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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=description content="JSON for Modern C++ is a header-only C++11 library that makes JSON a first-class data type."><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/integration/compile_times/" rel="canonical"><link href=../pkg-config/ rel=prev><link href=../../api/basic_json/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>Compile times - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel=stylesheet href=../../css/custom.css><link rel=stylesheet href=../../css/brand.css><link rel=stylesheet href=../../css/fig-sax.css><link rel=stylesheet href=../../css/fig-jsonview.css><link rel=stylesheet 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href=../../home/releases/v2.0.8/ class=md-nav__link> <span class=md-ellipsis> v2.0.8 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.7/ class=md-nav__link> <span class=md-ellipsis> v2.0.7 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.6/ class=md-nav__link> <span class=md-ellipsis> v2.0.6 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.5/ class=md-nav__link> <span class=md-ellipsis> v2.0.5 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.4/ class=md-nav__link> <span class=md-ellipsis> v2.0.4 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.3/ class=md-nav__link> <span class=md-ellipsis> v2.0.3 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.2/ class=md-nav__link> <span class=md-ellipsis> v2.0.2 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.1/ class=md-nav__link> <span class=md-ellipsis> v2.0.1 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v2.0.0/ class=md-nav__link> <span class=md-ellipsis> v2.0.0 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v1.1.0/ class=md-nav__link> <span class=md-ellipsis> v1.1.0 </span> </a> </li> <li class=md-nav__item> <a href=../../home/releases/v1.0.0/ class=md-nav__link> <span class=md-ellipsis> v1.0.0 </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../home/design_goals/ class=md-nav__link> <span class=md-ellipsis> Design goals </span> </a> </li> <li class=md-nav__item> <a href=../../home/architecture/ class=md-nav__link> <span class=md-ellipsis> Architecture </span> </a> </li> <li class=md-nav__item> <a href=../../home/customers/ class=md-nav__link> <span class=md-ellipsis> Customers </span> </a> </li> <li class=md-nav__item> <a href=../../home/sponsors/ class=md-nav__link> <span class=md-ellipsis> Sponsors </span> </a> </li> <li class=md-nav__item> <a href=../../home/debugging/ class=md-nav__link> <span class=md-ellipsis> Debugging </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2> <div class="md-nav__link md-nav__container"> <a href=../../features/ class="md-nav__link "> <span class=md-ellipsis> Features </span> </a> <label class="md-nav__link " for=__nav_2 id=__nav_2_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_2_label aria-expanded=false> <label class=md-nav__title for=__nav_2> <span class="md-nav__icon md-icon"></span> Features </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../features/arbitrary_types/ class=md-nav__link> <span class=md-ellipsis> Arbitrary Type Conversions </span> </a> </li> <li class=md-nav__item> <a href=../../features/type_recipes/ class=md-nav__link> <span class=md-ellipsis> Recipes for Common Types </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_4> <div class="md-nav__link md-nav__container"> <a href=../../features/binary_formats/ class="md-nav__link "> <span class=md-ellipsis> Binary Formats </span> </a> <label class="md-nav__link " for=__nav_2_4 id=__nav_2_4_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_4_label aria-expanded=false> <label class=md-nav__title for=__nav_2_4> <span class="md-nav__icon md-icon"></span> Binary Formats </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../features/binary_formats/bjdata/ class=md-nav__link> <span class=md-ellipsis> BJData </span> </a> </li> <li class=md-nav__item> <a href=../../features/binary_formats/bon8/ class=md-nav__link> <span class=md-ellipsis> BON8 </span> </a> </li> <li class=md-nav__item> <a href=../../features/binary_formats/bson/ class=md-nav__link> <span class=md-ellipsis> BSON </span> </a> </li> <li class=md-nav__item> <a href=../../features/binary_formats/cbor/ class=md-nav__link> <span class=md-ellipsis> CBOR </span> </a> </li> <li class=md-nav__item> <a href=../../features/binary_formats/messagepack/ class=md-nav__link> <span class=md-ellipsis> MessagePack </span> </a> </li> <li class=md-nav__item> <a href=../../features/binary_formats/ubjson/ class=md-nav__link> <span class=md-ellipsis> UBJSON </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../features/binary_values/ class=md-nav__link> <span class=md-ellipsis> Binary Values </span> </a> </li> <li class=md-nav__item> <a href=../../features/comments/ class=md-nav__link> <span class=md-ellipsis> Comments </span> </a> </li> <li class=md-nav__item> <a href=../../features/conversions/ class=md-nav__link> <span class=md-ellipsis> Converting values </span> </a> </li> <li class=md-nav__item> <a href=../../features/creating_values/ class=md-nav__link> <span class=md-ellipsis> Creating JSON values </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_9> <div class="md-nav__link md-nav__container"> <a href=../../features/element_access/ class="md-nav__link "> <span class=md-ellipsis> Element Access </span> </a> <label class="md-nav__link " for=__nav_2_9 id=__nav_2_9_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_9_label aria-expanded=false> <label class=md-nav__title for=__nav_2_9> <span class="md-nav__icon md-icon"></span> Element Access </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../features/element_access/unchecked_access/ class=md-nav__link> <span class=md-ellipsis> Unchecked access: operator[] </span> </a> </li> <li class=md-nav__item> <a href=../../features/element_access/checked_access/ class=md-nav__link> <span class=md-ellipsis> Checked access: at </span> </a> </li> <li class=md-nav__item> <a href=../../features/element_access/default_value/ class=md-nav__link> <span class=md-ellipsis> Access with default value: value </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../features/iterators/ class=md-nav__link> <span class=md-ellipsis> Iterators </span> </a> </li> <li class=md-nav__item> <a href=../../features/merge_patch/ class=md-nav__link> <span class=md-ellipsis> JSON Merge Patch </span> </a> </li> <li class=md-nav__item> <a href=../../features/json_patch/ class=md-nav__link> <span class=md-ellipsis> JSON Patch and Diff </span> </a> </li> <li class=md-nav__item> <a href=../../features/json_pointer/ class=md-nav__link> <span class=md-ellipsis> JSON Pointer </span> </a> </li> <li class=md-nav__item> <a href=../../features/modifying_values/ class=md-nav__link> <span class=md-ellipsis> Modifying values </span> </a> </li> <li class=md-nav__item> <a href=../../features/modules/ class=md-nav__link> <span class=md-ellipsis> Modules </span> </a> </li> <li class=md-nav__item> <a href=../../features/namespace/ class=md-nav__link> <span class=md-ellipsis> nlohmann Namespace </span> </a> </li> <li class=md-nav__item> <a href=../../features/no_exceptions/ class=md-nav__link> <span class=md-ellipsis> Working Without Exceptions </span> </a> </li> <li class=md-nav__item> <a href=../../features/object_order/ class=md-nav__link> <span class=md-ellipsis> Object Order </span> </a> </li> <li class=md-nav__item> <a href=../../features/performance/ class=md-nav__link> <span class=md-ellipsis> Performance </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_20> <div class="md-nav__link md-nav__container"> <a href=../../features/parsing/ class="md-nav__link "> <span class=md-ellipsis> Parsing </span> </a> <label class="md-nav__link " for=__nav_2_20 id=__nav_2_20_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_20_label aria-expanded=false> <label class=md-nav__title for=__nav_2_20> <span class="md-nav__icon md-icon"></span> Parsing </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../features/parsing/json_lines/ class=md-nav__link> <span class=md-ellipsis> JSON Lines </span> </a> </li> <li class=md-nav__item> <a href=../../features/parsing/large_and_partial_input/ class=md-nav__link> <span class=md-ellipsis> Large, Streamed, and Partial Input </span> </a> </li> <li class=md-nav__item> <a href=../../features/parsing/parse_exceptions/ class=md-nav__link> <span class=md-ellipsis> Parsing and Exceptions </span> </a> </li> <li class=md-nav__item> <a href=../../features/parsing/parser_callbacks/ class=md-nav__link> <span class=md-ellipsis> Parser Callbacks </span> </a> </li> <li class=md-nav__item> <a href=../../features/parsing/sax_interface/ class=md-nav__link> <span class=md-ellipsis> SAX Interface </span> </a> </li> <li class=md-nav__item> <a href=../../features/parsing/untrusted_input/ class=md-nav__link> <span class=md-ellipsis> Parsing Untrusted Input </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../features/assertions/ class=md-nav__link> <span class=md-ellipsis> Runtime Assertions </span> </a> </li> <li class=md-nav__item> <a href=../../features/serialization/ class=md-nav__link> <span class=md-ellipsis> Serialization </span> </a> </li> <li class=md-nav__item> <a href=../../features/enum_conversion/ class=md-nav__link> <span class=md-ellipsis> Specializing enum conversion </span> </a> </li> <li class=md-nav__item> <a href=../../features/macros/ class=md-nav__link> <span class=md-ellipsis> Supported Macros </span> </a> </li> <li class=md-nav__item> <a href=../../features/trailing_commas/ class=md-nav__link> <span class=md-ellipsis> Trailing Commas </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_2_26> <div class="md-nav__link md-nav__container"> <a href=../../features/types/ class="md-nav__link "> <span class=md-ellipsis> Types </span> </a> <label class="md-nav__link " for=__nav_2_26 id=__nav_2_26_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_2_26_label aria-expanded=false> <label class=md-nav__title for=__nav_2_26> <span class="md-nav__icon md-icon"></span> Types </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../features/types/number_handling/ class=md-nav__link> <span class=md-ellipsis> Number Handling </span> </a> </li> <li class=md-nav__item> <a href=../../features/types/template_parameters/ class=md-nav__link> <span class=md-ellipsis> Template Parameter Requirements </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../features/json_view/ class=md-nav__link> <span class=md-ellipsis> Zero-copy JSON views </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--active md-nav__item--section md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_3 checked> <div class="md-nav__link md-nav__container"> <a href=../ class="md-nav__link "> <span class=md-ellipsis> Integration </span> </a> <label class="md-nav__link " for=__nav_3 id=__nav_3_label tabindex> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_3_label aria-expanded=true> <label class=md-nav__title for=__nav_3> <span class="md-nav__icon md-icon"></span> Integration </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../migration_guide/ class=md-nav__link> <span class=md-ellipsis> Migration Guide </span> </a> </li> <li class=md-nav__item> <a href=../cmake/ class=md-nav__link> <span class=md-ellipsis> CMake </span> </a> </li> <li class=md-nav__item> <a href=../package_managers/ class=md-nav__link> <span class=md-ellipsis> Package Managers </span> </a> </li> <li class=md-nav__item> <a href=../pkg-config/ class=md-nav__link> <span class=md-ellipsis> Pkg-config </span> </a> </li> <li class="md-nav__item md-nav__item--active"> <input class="md-nav__toggle md-toggle" type=checkbox id=__toc> <label class="md-nav__link md-nav__link--active" for=__toc> <span class=md-ellipsis> Compile times </span> <span class="md-nav__icon md-icon"></span> </label> <a href=./ class="md-nav__link md-nav__link--active"> <span class=md-ellipsis> Compile times </span> </a> <nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class=md-nav__title for=__toc> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class=md-nav__list data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#include-json_fwdhpp-in-headers class=md-nav__link> <span class=md-ellipsis> Include json_fwd.hpp in headers </span> </a> </li> <li class=md-nav__item> <a href=#opt-out-of-the-automatic-user-defined-string-literals class=md-nav__link> <span class=md-ellipsis> Opt out of the automatic user-defined string literals </span> </a> </li> <li class=md-nav__item> <a href=#instantiate-basic_json-once class=md-nav__link> <span class=md-ellipsis> Instantiate basic_json once </span> </a> </li> <li class=md-nav__item> <a href=#switch-off-filesystem-support class=md-nav__link> <span class=md-ellipsis> Switch off filesystem support </span> </a> </li> <li class=md-nav__item> <a href=#use-c20-modules class=md-nav__link> <span class=md-ellipsis> Use C++20 modules </span> </a> </li> <li class=md-nav__item> <a href=#use-precompiled-headers class=md-nav__link> <span class=md-ellipsis> Use precompiled headers </span> </a> </li> <li class=md-nav__item> <a href=#options-without-effect-on-compile-times class=md-nav__link> <span class=md-ellipsis> Options without effect on compile times </span> </a> </li> <li class=md-nav__item> <a href=#see-also class=md-nav__link> <span class=md-ellipsis> See also </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4> <label class=md-nav__link for=__nav_4 id=__nav_4_label tabindex=0> <span class=md-ellipsis> API Documentation </span> <span class="md-nav__icon md-icon"></span> </label> <nav class=md-nav data-md-level=1 aria-labelledby=__nav_4_label aria-expanded=false> <label class=md-nav__title for=__nav_4> <span class="md-nav__icon md-icon"></span> API Documentation </label> <ul class=md-nav__list data-md-scrollfix> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_1> <div class="md-nav__link md-nav__container"> <a href=../../api/basic_json/ class="md-nav__link "> <span class=md-ellipsis> basic_json </span> </a> <label class="md-nav__link " for=__nav_4_1 id=__nav_4_1_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_1_label aria-expanded=false> <label class=md-nav__title for=__nav_4_1> <span class="md-nav__icon md-icon"></span> basic_json </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/basic_json/basic_json/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/~basic_json/ class=md-nav__link> <span class=md-ellipsis> (Destructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/accept/ class=md-nav__link> <span class=md-ellipsis> accept </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/array/ class=md-nav__link> <span class=md-ellipsis> array </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/array_t/ class=md-nav__link> <span class=md-ellipsis> array_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/as_base_class/ class=md-nav__link> <span class=md-ellipsis> as_base_class </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/at/ class=md-nav__link> <span class=md-ellipsis> at </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/back/ class=md-nav__link> <span class=md-ellipsis> back </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/begin/ class=md-nav__link> <span class=md-ellipsis> begin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/binary/ class=md-nav__link> <span class=md-ellipsis> binary </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/binary_t/ class=md-nav__link> <span class=md-ellipsis> binary_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/bjdata_version_t/ class=md-nav__link> <span class=md-ellipsis> bjdata_version_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/boolean_t/ class=md-nav__link> <span class=md-ellipsis> boolean_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/cbegin/ class=md-nav__link> <span class=md-ellipsis> cbegin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/cbor_tag_handler_t/ class=md-nav__link> <span class=md-ellipsis> cbor_tag_handler_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/cend/ class=md-nav__link> <span class=md-ellipsis> cend </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/clear/ class=md-nav__link> <span class=md-ellipsis> clear </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/contains/ class=md-nav__link> <span class=md-ellipsis> contains </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/count/ class=md-nav__link> <span class=md-ellipsis> count </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/crbegin/ class=md-nav__link> <span class=md-ellipsis> crbegin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/crend/ class=md-nav__link> <span class=md-ellipsis> crend </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/default_object_comparator_t/ class=md-nav__link> <span class=md-ellipsis> default_object_comparator_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/diff/ class=md-nav__link> <span class=md-ellipsis> diff </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/dump/ class=md-nav__link> <span class=md-ellipsis> dump </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/emplace/ class=md-nav__link> <span class=md-ellipsis> emplace </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/emplace_back/ class=md-nav__link> <span class=md-ellipsis> emplace_back </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/empty/ class=md-nav__link> <span class=md-ellipsis> empty </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/end/ class=md-nav__link> <span class=md-ellipsis> end </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/end_pos/ class=md-nav__link> <span class=md-ellipsis> end_pos </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/erase/ class=md-nav__link> <span class=md-ellipsis> erase </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/error_handler_t/ class=md-nav__link> <span class=md-ellipsis> error_handler_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/exception/ class=md-nav__link> <span class=md-ellipsis> exception </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/find/ class=md-nav__link> <span class=md-ellipsis> find </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/flatten/ class=md-nav__link> <span class=md-ellipsis> flatten </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/format_as/ class=md-nav__link> <span class=md-ellipsis> format_as </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_bjdata/ class=md-nav__link> <span class=md-ellipsis> from_bjdata </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_bon8/ class=md-nav__link> <span class=md-ellipsis> from_bon8 </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_bson/ class=md-nav__link> <span class=md-ellipsis> from_bson </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_cbor/ class=md-nav__link> <span class=md-ellipsis> from_cbor </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_msgpack/ class=md-nav__link> <span class=md-ellipsis> from_msgpack </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/from_ubjson/ class=md-nav__link> <span class=md-ellipsis> from_ubjson </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/front/ class=md-nav__link> <span class=md-ellipsis> front </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get/ class=md-nav__link> <span class=md-ellipsis> get </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get_allocator/ class=md-nav__link> <span class=md-ellipsis> get_allocator </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get_binary/ class=md-nav__link> <span class=md-ellipsis> get_binary </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get_ptr/ class=md-nav__link> <span class=md-ellipsis> get_ptr </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get_ref/ class=md-nav__link> <span class=md-ellipsis> get_ref </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/get_to/ class=md-nav__link> <span class=md-ellipsis> get_to </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/std_formatter/ class=md-nav__link> <span class=md-ellipsis> std::formatter&lt;basic_json&gt; </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/std_hash/ class=md-nav__link> <span class=md-ellipsis> std::hash&lt;basic_json&gt; </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/input_format_t/ class=md-nav__link> <span class=md-ellipsis> input_format_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/insert/ class=md-nav__link> <span class=md-ellipsis> insert </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/invalid_iterator/ class=md-nav__link> <span class=md-ellipsis> invalid_iterator </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_array/ class=md-nav__link> <span class=md-ellipsis> is_array </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_binary/ class=md-nav__link> <span class=md-ellipsis> is_binary </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_boolean/ class=md-nav__link> <span class=md-ellipsis> is_boolean </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_discarded/ class=md-nav__link> <span class=md-ellipsis> is_discarded </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_null/ class=md-nav__link> <span class=md-ellipsis> is_null </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_number/ class=md-nav__link> <span class=md-ellipsis> is_number </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_number_float/ class=md-nav__link> <span class=md-ellipsis> is_number_float </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_number_integer/ class=md-nav__link> <span class=md-ellipsis> is_number_integer </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_number_unsigned/ class=md-nav__link> <span class=md-ellipsis> is_number_unsigned </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_object/ class=md-nav__link> <span class=md-ellipsis> is_object </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_primitive/ class=md-nav__link> <span class=md-ellipsis> is_primitive </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_string/ class=md-nav__link> <span class=md-ellipsis> is_string </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/is_structured/ class=md-nav__link> <span class=md-ellipsis> is_structured </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/items/ class=md-nav__link> <span class=md-ellipsis> items </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/json_base_class_t/ class=md-nav__link> <span class=md-ellipsis> json_base_class_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/json_serializer/ class=md-nav__link> <span class=md-ellipsis> json_serializer </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/max_size/ class=md-nav__link> <span class=md-ellipsis> max_size </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/meta/ class=md-nav__link> <span class=md-ellipsis> meta </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/merge_diff/ class=md-nav__link> <span class=md-ellipsis> merge_diff </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/merge_patch/ class=md-nav__link> <span class=md-ellipsis> merge_patch </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/number_float_t/ class=md-nav__link> <span class=md-ellipsis> number_float_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/number_integer_t/ class=md-nav__link> <span class=md-ellipsis> number_integer_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/number_unsigned_t/ class=md-nav__link> <span class=md-ellipsis> number_unsigned_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/object/ class=md-nav__link> <span class=md-ellipsis> object </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/object_comparator_t/ class=md-nav__link> <span class=md-ellipsis> object_comparator_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/object_t/ class=md-nav__link> <span class=md-ellipsis> object_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_ValueType/ class=md-nav__link> <span class=md-ellipsis> operator ValueType </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_value_t/ class=md-nav__link> <span class=md-ellipsis> operator value_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator%5B%5D/ class=md-nav__link> <span class=md-ellipsis> operator[] </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator%3D/ class=md-nav__link> <span class=md-ellipsis> operator= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator%2B%3D/ class=md-nav__link> <span class=md-ellipsis> operator+= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_lt/ class=md-nav__link> <span class=md-ellipsis> operator< </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_gt/ class=md-nav__link> <span class=md-ellipsis> operator> </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_le/ class=md-nav__link> <span class=md-ellipsis> operator<= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_ge/ class=md-nav__link> <span class=md-ellipsis> operator>= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/operator_spaceship/ class=md-nav__link> <span class=md-ellipsis> operator<=> </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/out_of_range/ class=md-nav__link> <span class=md-ellipsis> out_of_range </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/other_error/ class=md-nav__link> <span class=md-ellipsis> other_error </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/parse/ class=md-nav__link> <span class=md-ellipsis> parse </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/parse_error/ class=md-nav__link> <span class=md-ellipsis> parse_error </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/parse_event_t/ class=md-nav__link> <span class=md-ellipsis> parse_event_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/parser_callback_t/ class=md-nav__link> <span class=md-ellipsis> parser_callback_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/patch/ class=md-nav__link> <span class=md-ellipsis> patch </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/patch_inplace/ class=md-nav__link> <span class=md-ellipsis> patch_inplace </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/push_back/ class=md-nav__link> <span class=md-ellipsis> push_back </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/rbegin/ class=md-nav__link> <span class=md-ellipsis> rbegin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/rend/ class=md-nav__link> <span class=md-ellipsis> rend </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/sax_parse/ class=md-nav__link> <span class=md-ellipsis> sax_parse </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/size/ class=md-nav__link> <span class=md-ellipsis> size </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/start_pos/ class=md-nav__link> <span class=md-ellipsis> start_pos </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/string_t/ class=md-nav__link> <span class=md-ellipsis> string_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/swap/ class=md-nav__link> <span class=md-ellipsis> swap </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/std_swap/ class=md-nav__link> <span class=md-ellipsis> std::swap&lt;basic_json&gt; </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_bjdata/ class=md-nav__link> <span class=md-ellipsis> to_bjdata </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_bon8/ class=md-nav__link> <span class=md-ellipsis> to_bon8 </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_bson/ class=md-nav__link> <span class=md-ellipsis> to_bson </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_cbor/ class=md-nav__link> <span class=md-ellipsis> to_cbor </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_msgpack/ class=md-nav__link> <span class=md-ellipsis> to_msgpack </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_string/ class=md-nav__link> <span class=md-ellipsis> to_string </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/to_ubjson/ class=md-nav__link> <span class=md-ellipsis> to_ubjson </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/type/ class=md-nav__link> <span class=md-ellipsis> type </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/type_error/ class=md-nav__link> <span class=md-ellipsis> type_error </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/type_name/ class=md-nav__link> <span class=md-ellipsis> type_name </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/unflatten/ class=md-nav__link> <span class=md-ellipsis> unflatten </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/update/ class=md-nav__link> <span class=md-ellipsis> update </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/value/ class=md-nav__link> <span class=md-ellipsis> value </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/value_t/ class=md-nav__link> <span class=md-ellipsis> value_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json/with_t/ class=md-nav__link> <span class=md-ellipsis> with_t </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_2> <div class="md-nav__link md-nav__container"> <a href=../../api/basic_json_document/ class="md-nav__link "> <span class=md-ellipsis> basic_json_document </span> </a> <label class="md-nav__link " for=__nav_4_2 id=__nav_4_2_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_2_label aria-expanded=false> <label class=md-nav__title for=__nav_4_2> <span class="md-nav__icon md-icon"></span> basic_json_document </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/basic_json_document/basic_json_document/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/accept/ class=md-nav__link> <span class=md-ellipsis> accept </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/erase/ class=md-nav__link> <span class=md-ellipsis> erase </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/insert/ class=md-nav__link> <span class=md-ellipsis> insert </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/is_discarded/ class=md-nav__link> <span class=md-ellipsis> is_discarded </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/load/ class=md-nav__link> <span class=md-ellipsis> load </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/memory_usage/ class=md-nav__link> <span class=md-ellipsis> memory_usage </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/node_count/ class=md-nav__link> <span class=md-ellipsis> node_count </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/owns_source/ class=md-nav__link> <span class=md-ellipsis> owns_source </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/parse/ class=md-nav__link> <span class=md-ellipsis> parse </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/parse_copy/ class=md-nav__link> <span class=md-ellipsis> parse_copy </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/push_back/ class=md-nav__link> <span class=md-ellipsis> push_back </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/read/ class=md-nav__link> <span class=md-ellipsis> read </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/root/ class=md-nav__link> <span class=md-ellipsis> root </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/save/ class=md-nav__link> <span class=md-ellipsis> save </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/set/ class=md-nav__link> <span class=md-ellipsis> set </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/shrink_to_fit/ class=md-nav__link> <span class=md-ellipsis> shrink_to_fit </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_document/source/ class=md-nav__link> <span class=md-ellipsis> source </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_3> <div class="md-nav__link md-nav__container"> <a href=../../api/basic_json_view/ class="md-nav__link "> <span class=md-ellipsis> basic_json_view </span> </a> <label class="md-nav__link " for=__nav_4_3 id=__nav_4_3_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_3_label aria-expanded=false> <label class=md-nav__title for=__nav_4_3> <span class="md-nav__icon md-icon"></span> basic_json_view </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/basic_json_view/basic_json_view/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/at/ class=md-nav__link> <span class=md-ellipsis> at </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/back/ class=md-nav__link> <span class=md-ellipsis> back </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/begin/ class=md-nav__link> <span class=md-ellipsis> begin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/cbegin/ class=md-nav__link> <span class=md-ellipsis> cbegin </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/cend/ class=md-nav__link> <span class=md-ellipsis> cend </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/contains/ class=md-nav__link> <span class=md-ellipsis> contains </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/count/ class=md-nav__link> <span class=md-ellipsis> count </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/dump/ class=md-nav__link> <span class=md-ellipsis> dump </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/empty/ class=md-nav__link> <span class=md-ellipsis> empty </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/end/ class=md-nav__link> <span class=md-ellipsis> end </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/find/ class=md-nav__link> <span class=md-ellipsis> find </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/front/ class=md-nav__link> <span class=md-ellipsis> front </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/get/ class=md-nav__link> <span class=md-ellipsis> get </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/get_string/ class=md-nav__link> <span class=md-ellipsis> get_string </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/get_to/ class=md-nav__link> <span class=md-ellipsis> get_to </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_array/ class=md-nav__link> <span class=md-ellipsis> is_array </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_binary/ class=md-nav__link> <span class=md-ellipsis> is_binary </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_boolean/ class=md-nav__link> <span class=md-ellipsis> is_boolean </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_discarded/ class=md-nav__link> <span class=md-ellipsis> is_discarded </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_null/ class=md-nav__link> <span class=md-ellipsis> is_null </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_number/ class=md-nav__link> <span class=md-ellipsis> is_number </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_number_float/ class=md-nav__link> <span class=md-ellipsis> is_number_float </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_number_integer/ class=md-nav__link> <span class=md-ellipsis> is_number_integer </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_number_unsigned/ class=md-nav__link> <span class=md-ellipsis> is_number_unsigned </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_object/ class=md-nav__link> <span class=md-ellipsis> is_object </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_primitive/ class=md-nav__link> <span class=md-ellipsis> is_primitive </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_string/ class=md-nav__link> <span class=md-ellipsis> is_string </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/is_structured/ class=md-nav__link> <span class=md-ellipsis> is_structured </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/items/ class=md-nav__link> <span class=md-ellipsis> items </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/materialize/ class=md-nav__link> <span class=md-ellipsis> materialize </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/number_format/ class=md-nav__link> <span class=md-ellipsis> number_format </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/number_token/ class=md-nav__link> <span class=md-ellipsis> number_token </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/operator_ltlt/ class=md-nav__link> <span class=md-ellipsis> operator<< </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/operator%5B%5D/ class=md-nav__link> <span class=md-ellipsis> operator[] </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/size/ class=md-nav__link> <span class=md-ellipsis> size </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/source_offset/ class=md-nav__link> <span class=md-ellipsis> source_offset </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/type/ class=md-nav__link> <span class=md-ellipsis> type </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/type_name/ class=md-nav__link> <span class=md-ellipsis> type_name </span> </a> </li> <li class=md-nav__item> <a href=../../api/basic_json_view/value/ class=md-nav__link> <span class=md-ellipsis> value </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_4> <div class="md-nav__link md-nav__container"> <a href=../../api/byte_container_with_subtype/ class="md-nav__link "> <span class=md-ellipsis> byte_container_with_subtype </span> </a> <label class="md-nav__link " for=__nav_4_4 id=__nav_4_4_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_4_label aria-expanded=false> <label class=md-nav__title for=__nav_4_4> <span class="md-nav__icon md-icon"></span> byte_container_with_subtype </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/byte_container_with_subtype/ class=md-nav__link> <span class=md-ellipsis> (constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/clear_subtype/ class=md-nav__link> <span class=md-ellipsis> clear_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/has_subtype/ class=md-nav__link> <span class=md-ellipsis> has_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/set_subtype/ class=md-nav__link> <span class=md-ellipsis> set_subtype </span> </a> </li> <li class=md-nav__item> <a href=../../api/byte_container_with_subtype/subtype/ class=md-nav__link> <span class=md-ellipsis> subtype </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_5> <div class="md-nav__link md-nav__container"> <a href=../../api/adl_serializer/ class="md-nav__link "> <span class=md-ellipsis> adl_serializer </span> </a> <label class="md-nav__link " for=__nav_4_5 id=__nav_4_5_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_5_label aria-expanded=false> <label class=md-nav__title for=__nav_4_5> <span class="md-nav__icon md-icon"></span> adl_serializer </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/adl_serializer/from_json/ class=md-nav__link> <span class=md-ellipsis> from_json </span> </a> </li> <li class=md-nav__item> <a href=../../api/adl_serializer/to_json/ class=md-nav__link> <span class=md-ellipsis> to_json </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../api/is_json_view/ class=md-nav__link> <span class=md-ellipsis> is_json_view </span> </a> </li> <li class=md-nav__item> <a href=../../api/json/ class=md-nav__link> <span class=md-ellipsis> json </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_document/ class=md-nav__link> <span class=md-ellipsis> json_document </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_editable_document/ class=md-nav__link> <span class=md-ellipsis> json_editable_document </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_editable_view/ class=md-nav__link> <span class=md-ellipsis> json_editable_view </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_11> <div class="md-nav__link md-nav__container"> <a href=../../api/json_pointer/ class="md-nav__link "> <span class=md-ellipsis> json_pointer </span> </a> <label class="md-nav__link " for=__nav_4_11 id=__nav_4_11_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_11_label aria-expanded=false> <label class=md-nav__title for=__nav_4_11> <span class="md-nav__icon md-icon"></span> json_pointer </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/json_pointer/json_pointer/ class=md-nav__link> <span class=md-ellipsis> (Constructor) </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/back/ class=md-nav__link> <span class=md-ellipsis> back </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/empty/ class=md-nav__link> <span class=md-ellipsis> empty </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/front/ class=md-nav__link> <span class=md-ellipsis> front </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_string_t/ class=md-nav__link> <span class=md-ellipsis> operator string_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_eq/ class=md-nav__link> <span class=md-ellipsis> operator== </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_ne/ class=md-nav__link> <span class=md-ellipsis> operator!= </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_spaceship/ class=md-nav__link> <span class=md-ellipsis> operator<=> </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_slash/ class=md-nav__link> <span class=md-ellipsis> operator/ </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/operator_slasheq/ class=md-nav__link> <span class=md-ellipsis> operator/= </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/parent_pointer/ class=md-nav__link> <span class=md-ellipsis> parent_pointer </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/pop_back/ class=md-nav__link> <span class=md-ellipsis> pop_back </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/pop_front/ class=md-nav__link> <span class=md-ellipsis> pop_front </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/push_back/ class=md-nav__link> <span class=md-ellipsis> push_back </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/push_front/ class=md-nav__link> <span class=md-ellipsis> push_front </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/string_t/ class=md-nav__link> <span class=md-ellipsis> string_t </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_pointer/to_string/ class=md-nav__link> <span class=md-ellipsis> to_string </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_12> <div class="md-nav__link md-nav__container"> <a href=../../api/json_sax/ class="md-nav__link "> <span class=md-ellipsis> json_sax </span> </a> <label class="md-nav__link " for=__nav_4_12 id=__nav_4_12_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_12_label aria-expanded=false> <label class=md-nav__title for=__nav_4_12> <span class="md-nav__icon md-icon"></span> json_sax </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/json_sax/binary/ class=md-nav__link> <span class=md-ellipsis> binary </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/boolean/ class=md-nav__link> <span class=md-ellipsis> boolean </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/end_array/ class=md-nav__link> <span class=md-ellipsis> end_array </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/end_object/ class=md-nav__link> <span class=md-ellipsis> end_object </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/key/ class=md-nav__link> <span class=md-ellipsis> key </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/null/ class=md-nav__link> <span class=md-ellipsis> null </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/number_float/ class=md-nav__link> <span class=md-ellipsis> number_float </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/number_integer/ class=md-nav__link> <span class=md-ellipsis> number_integer </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/number_unsigned/ class=md-nav__link> <span class=md-ellipsis> number_unsigned </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/parse_error/ class=md-nav__link> <span class=md-ellipsis> parse_error </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/start_array/ class=md-nav__link> <span class=md-ellipsis> start_array </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/start_object/ class=md-nav__link> <span class=md-ellipsis> start_object </span> </a> </li> <li class=md-nav__item> <a href=../../api/json_sax/string/ class=md-nav__link> <span class=md-ellipsis> string </span> </a> </li> </ul> </nav> </li> <li class=md-nav__item> <a href=../../api/json_view/ class=md-nav__link> <span class=md-ellipsis> json_view </span> </a> </li> <li class=md-nav__item> <a href=../../api/operator_ltlt/ class=md-nav__link> <span class=md-ellipsis> operator<<(basic_json), operator<<(json_pointer) </span> </a> </li> <li class=md-nav__item> <a href=../../api/operator_gtgt/ class=md-nav__link> <span class=md-ellipsis> operator>>(basic_json) </span> </a> </li> <li class=md-nav__item> <a href=../../api/operator_literal_json/ class=md-nav__link> <span class=md-ellipsis> operator""_json </span> </a> </li> <li class=md-nav__item> <a href=../../api/operator_literal_json_pointer/ class=md-nav__link> <span class=md-ellipsis> operator""_json_pointer </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_json/ class=md-nav__link> <span class=md-ellipsis> ordered_json </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_json_document/ class=md-nav__link> <span class=md-ellipsis> ordered_json_document </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_json_editable_document/ class=md-nav__link> <span class=md-ellipsis> ordered_json_editable_document </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_json_editable_view/ class=md-nav__link> <span class=md-ellipsis> ordered_json_editable_view </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_json_view/ class=md-nav__link> <span class=md-ellipsis> ordered_json_view </span> </a> </li> <li class=md-nav__item> <a href=../../api/ordered_map/ class=md-nav__link> <span class=md-ellipsis> ordered_map </span> </a> </li> <li class=md-nav__item> <a href=../../api/view_mode/ class=md-nav__link> <span class=md-ellipsis> view_mode </span> </a> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_4_25> <div class="md-nav__link md-nav__container"> <a href=../../api/macros/ class="md-nav__link "> <span class=md-ellipsis> macros </span> </a> <label class="md-nav__link " for=__nav_4_25 id=__nav_4_25_label tabindex=0> <span class="md-nav__icon md-icon"></span> </label> </div> <nav class=md-nav data-md-level=2 aria-labelledby=__nav_4_25_label aria-expanded=false> <label class=md-nav__title for=__nav_4_25> <span class="md-nav__icon md-icon"></span> macros </label> <ul class=md-nav__list data-md-scrollfix> <li class=md-nav__item> <a href=../../api/macros/json_assert/ class=md-nav__link> <span class=md-ellipsis> JSON_ASSERT </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_brace_init_copy_semantics/ class=md-nav__link> <span class=md-ellipsis> JSON_BRACE_INIT_COPY_SEMANTICS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_throw_user/ class=md-nav__link> <span class=md-ellipsis> JSON_CATCH_USER, JSON_THROW_USER, JSON_TRY_USER </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_diagnostics/ class=md-nav__link> <span class=md-ellipsis> JSON_DIAGNOSTICS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_delete_deprecated_functions/ class=md-nav__link> <span class=md-ellipsis> JSON_DELETE_DEPRECATED_FUNCTIONS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_diagnostic_positions/ class=md-nav__link> <span class=md-ellipsis> JSON_DIAGNOSTIC_POSITIONS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_disable_enum_serialization/ class=md-nav__link> <span class=md-ellipsis> JSON_DISABLE_ENUM_SERIALIZATION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_disable_stream_bulk_scan/ class=md-nav__link> <span class=md-ellipsis> JSON_DISABLE_STREAM_BULK_SCAN </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_disable_tuple_reference_conversion/ class=md-nav__link> <span class=md-ellipsis> JSON_DISABLE_TUPLE_REFERENCE_CONVERSION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_disable_unlocked_file_io/ class=md-nav__link> <span class=md-ellipsis> JSON_DISABLE_UNLOCKED_FILE_IO </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_cpp_11/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_CPP_11, JSON_HAS_CPP_14, JSON_HAS_CPP_17, JSON_HAS_CPP_20, JSON_HAS_CPP_23, JSON_HAS_CPP_26 </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_filesystem/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_EXPERIMENTAL_FILESYSTEM, JSON_HAS_FILESYSTEM </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_range_view_conversion/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_RANGE_VIEW_CONVERSION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_ranges/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_RANGES </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_static_rtti/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_STATIC_RTTI </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_std_format/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_STD_FORMAT </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_has_three_way_comparison/ class=md-nav__link> <span class=md-ellipsis> JSON_HAS_THREE_WAY_COMPARISON </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_no_automatic_udls/ class=md-nav__link> <span class=md-ellipsis> JSON_NO_AUTOMATIC_UDLS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_noexception/ class=md-nav__link> <span class=md-ellipsis> JSON_NOEXCEPTION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_no_io/ class=md-nav__link> <span class=md-ellipsis> JSON_NO_IO </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_no_simd/ class=md-nav__link> <span class=md-ellipsis> JSON_NO_SIMD </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_no_thread_local/ class=md-nav__link> <span class=md-ellipsis> JSON_NO_THREAD_LOCAL </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_precise_stream_position/ class=md-nav__link> <span class=md-ellipsis> JSON_PRECISE_STREAM_POSITION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_skip_library_version_check/ class=md-nav__link> <span class=md-ellipsis> JSON_SKIP_LIBRARY_VERSION_CHECK </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_skip_unsupported_compiler_check/ class=md-nav__link> <span class=md-ellipsis> JSON_SKIP_UNSUPPORTED_COMPILER_CHECK </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_strict_binary_utf8/ class=md-nav__link> <span class=md-ellipsis> JSON_STRICT_BINARY_UTF8 </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_strict_nul_handling/ class=md-nav__link> <span class=md-ellipsis> JSON_STRICT_NUL_HANDLING </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_use_global_udls/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_GLOBAL_UDLS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_use_implicit_conversions/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_IMPLICIT_CONVERSIONS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_use_legacy_discarded_value_comparison/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_use_objects_for_enum_keyed_maps/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/json_use_simdutf/ class=md-nav__link> <span class=md-ellipsis> JSON_USE_SIMDUTF </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_define_derived_type/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_define_type_intrusive/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_define_type_non_intrusive/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_define_type_with_names/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES, NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_namespace/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_namespace_begin/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_BEGIN, NLOHMANN_JSON_NAMESPACE_END </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_namespace_no_version/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_NAMESPACE_NO_VERSION </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_serialize_enum/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_SERIALIZE_ENUM </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_serialize_enum_strict/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_SERIALIZE_ENUM_STRICT </span> </a> </li> <li class=md-nav__item> <a href=../../api/macros/nlohmann_json_version_major/ class=md-nav__link> <span class=md-ellipsis> NLOHMANN_JSON_VERSION_MAJOR, NLOHMANN_JSON_VERSION_MINOR, NLOHMANN_JSON_VERSION_PATCH </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type=checkbox id=__nav_5> <div class="md-nav__link md-nav__container"> <a href=../../community/ 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data-md-component=toc data-md-scrollfix> <li class=md-nav__item> <a href=#include-json_fwdhpp-in-headers class=md-nav__link> <span class=md-ellipsis> Include json_fwd.hpp in headers </span> </a> </li> <li class=md-nav__item> <a href=#opt-out-of-the-automatic-user-defined-string-literals class=md-nav__link> <span class=md-ellipsis> Opt out of the automatic user-defined string literals </span> </a> </li> <li class=md-nav__item> <a href=#instantiate-basic_json-once class=md-nav__link> <span class=md-ellipsis> Instantiate basic_json once </span> </a> </li> <li class=md-nav__item> <a href=#switch-off-filesystem-support class=md-nav__link> <span class=md-ellipsis> Switch off filesystem support </span> </a> </li> <li class=md-nav__item> <a href=#use-c20-modules class=md-nav__link> <span class=md-ellipsis> Use C++20 modules </span> </a> </li> <li class=md-nav__item> <a href=#use-precompiled-headers class=md-nav__link> <span class=md-ellipsis> Use precompiled headers </span> </a> </li> <li class=md-nav__item> <a href=#options-without-effect-on-compile-times class=md-nav__link> <span class=md-ellipsis> Options without effect on compile times </span> </a> </li> <li class=md-nav__item> <a href=#see-also class=md-nav__link> <span class=md-ellipsis> See also </span> </a> </li> </ul> </nav> </div> </div> </div> <div class=md-content data-md-component=content> <article class="md-content__inner md-typeset"> <a href="https://github.com/nlohmann/json/edit/develop/docs/mkdocs/docs/integration/compile_times.md" title="Edit this page" class="md-content__button md-icon" rel="edit"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M10 20H6V4h7v5h5v3.1l2-2V8l-6-6H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h4zm10.2-7c.1 0 .3.1.4.2l1.3 1.3c.2.2.2.6 0 .8l-1 1-2.1-2.1 1-1c.1-.1.2-.2.4-.2m0 3.9L14.1 23H12v-2.1l6.1-6.1z"/></svg> </a> <a href="https://github.com/nlohmann/json/raw/develop/docs/mkdocs/docs/integration/compile_times.md" title="View source of this page" class="md-content__button md-icon"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M17 18c.56 0 1 .44 1 1s-.44 1-1 1-1-.44-1-1 .44-1 1-1m0-3c-2.73 0-5.06 1.66-6 4 .94 2.34 3.27 4 6 4s5.06-1.66 6-4c-.94-2.34-3.27-4-6-4m0 6.5a2.5 2.5 0 0 1-2.5-2.5 2.5 2.5 0 0 1 2.5-2.5 2.5 2.5 0 0 1 2.5 2.5 2.5 2.5 0 0 1-2.5 2.5M9.27 20H6V4h7v5h5v4.07c.7.08 1.36.25 2 .49V8l-6-6H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h4.5a8.2 8.2 0 0 1-1.23-2"/></svg> </a> <h1 id=compile-times>Compile times<a class=headerlink href=#compile-times title="Permanent link">&para;</a></h1> <p>The library is header-only and makes heavy use of templates, so every translation unit that includes <code>&lt;nlohmann/json.hpp&gt;</code> pays for parsing the header and instantiating what it uses. This page lists the options to reduce that cost, ordered by how much they typically save.</p> <div class="admonition info"> <p class=admonition-title>Measurements</p> <p>The numbers below are medians of the wall-clock time of nine runs compiling a single translation unit with <code>-std=c++17 -c</code> against the single-header version, with Apple clang 21.0.0 (clang-2100.3.34.2) and Homebrew <abbr title="GNU Compiler Collection">GCC</abbr> 16.2.0 on macOS (Apple M1 Max). All configurations were run interleaved, in alternating order. They show the order of magnitude to expect; measure your own code before and after a change.</p> <p>The translation units are listed below. They replace the ones used for earlier versions of this page, whose sources were not published, so the numbers differ from earlier versions.</p> </div> <details class=example> <summary>Measured translation units</summary> <p>The <em>model</em> and <em>parsing</em> translation units start with <code>#include &lt;string&gt;</code>, <code>#include &lt;vector&gt;</code>, and <code>#include &lt;nlohmann/json.hpp&gt;</code>; the <em>header-only</em> translation unit includes only the library header.</p> <div class=highlight><span class=filename>model translation unit</span><pre><span></span><code><span class=k>struct</span><span class=w> </span><span class=nc>person</span>
<span class=p>{</span>
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=w> </span><span class=n>name</span><span class=p>;</span>
<span class=w> </span><span class=kt>int</span><span class=w> </span><span class=n>age</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=mi>0</span><span class=p>;</span>
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>vector</span><span class=o>&lt;</span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=o>&gt;</span><span class=w> </span><span class=n>tags</span><span class=p>;</span>
<span class=p>};</span>
<span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>)</span>
<span class=p>{</span>
<span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=p>{{</span><span class=s>"name"</span><span class=p>,</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>name</span><span class=p>},</span><span class=w> </span><span class=p>{</span><span class=s>"age"</span><span class=p>,</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>},</span><span class=w> </span><span class=p>{</span><span class=s>"tags"</span><span class=p>,</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>tags</span><span class=p>}};</span>
<span class=p>}</span>
<span class=kt>void</span><span class=w> </span><span class=nf>from_json</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>)</span>
<span class=p>{</span>
<span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>"name"</span><span class=p>).</span><span class=n>get_to</span><span class=p>(</span><span class=n>p</span><span class=p>.</span><span class=n>name</span><span class=p>);</span>
<span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>"age"</span><span class=p>).</span><span class=n>get_to</span><span class=p>(</span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>);</span>
<span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>at</span><span class=p>(</span><span class=s>"tags"</span><span class=p>).</span><span class=n>get_to</span><span class=p>(</span><span class=n>p</span><span class=p>.</span><span class=n>tags</span><span class=p>);</span>
<span class=p>}</span>
<span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=nf>roundtrip</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>)</span>
<span class=p>{</span>
<span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>;</span>
<span class=w> </span><span class=k>return</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=p>(</span><span class=n>j</span><span class=p>.</span><span class=n>get</span><span class=o>&lt;</span><span class=n>person</span><span class=o>&gt;</span><span class=p>());</span>
<span class=p>}</span>
</code></pre></div> <div class=highlight><span class=filename>parsing translation unit</span><pre><span></span><code><span class=n>std</span><span class=o>::</span><span class=kt>size_t</span><span class=w> </span><span class=nf>parse_and_dump</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>string</span><span class=o>&amp;</span><span class=w> </span><span class=n>s</span><span class=p>)</span>
<span class=p>{</span>
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=n>s</span><span class=p>);</span>
<span class=w> </span><span class=k>return</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>dump</span><span class=p>(</span><span class=mi>2</span><span class=p>).</span><span class=n>size</span><span class=p>();</span>
<span class=p>}</span>
</code></pre></div> <div class=highlight><span class=filename>header-only translation unit</span><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span><span class=w> </span><span class=c1>// or &lt;nlohmann/json_fwd.hpp&gt;</span>
<span class=k>struct</span><span class=w> </span><span class=nc>person</span><span class=p>;</span>
<span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>);</span>
<span class=kt>void</span><span class=w> </span><span class=nf>from_json</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>);</span>
</code></pre></div> </details> <div class=nj-fig-wrap> <p><svg class="nj-fig nj-charts nj-charts--compile" viewbox="0 0 470 516" role=img aria-labelledby="nj-charts-ct nj-charts-ct-d" xmlns=http://www.w3.org/2000/svg> <title id=nj-charts-ct>Change in compile time against the default configuration at -O0, Apple clang and G&#8203;CC 16</title> <desc id=nj-charts-ct-d>Grouped horizontal bars, negative is faster. json_fwd.hpp instead of json.hpp on a header-only translation unit: Apple clang -62 %, G&#8203;CC 16 -82 %; extern template on a parsing translation unit: Apple clang -7 %, G&#8203;CC 16 -21 %; JSON_NO_AUTOMATIC_UDLS on a model translation unit: Apple clang -11 %, G&#8203;CC 16 -11 %; JSON_NO_AUTOMATIC_UDLS on a parsing translation unit: Apple clang -1 %, G&#8203;CC 16 -2 %; JSON_HAS_FILESYSTEM=0 + JSON_NO_IO on a model translation unit: Apple clang -8 %, G&#8203;CC 16 -11 %; JSON_HAS_FILESYSTEM=0 on a model translation unit: Apple clang -5 %, G&#8203;CC 16 -9 %; JSON_NO_IO on a model translation unit: Apple clang -2 %, G&#8203;CC 16 -2 %; 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model TU*</tspan></text> <path class=nj-charts-clang d="M362.6 382 H358.72 Q354.72 382 354.72 386 V390 Q354.72 394 358.72 394 H362.6 Z"><title>JSON_NO_IO, model TU (Apple clang): &#8722;2 %</title></path> <text class=nj-charts-val x=367.6 y=392.5>&#8722;2 %</text> <path class=nj-charts-gcc d="M362.6 396 H358.72 Q354.72 396 354.72 400 V404 Q354.72 408 358.72 408 H362.6 Z"><title>JSON_NO_IO, model TU (G&#8203;CC 16): &#8722;2 %</title></path> <text class=nj-charts-val x=367.6 y=406.5>&#8722;2 %</text> <text class=nj-charts-rowlabel x=8 y=426><tspan class=nj-charts-code>JSON_USE_GLOBAL_UDLS=0</tspan><tspan class=nj-charts-sub> &#183; model TU*</tspan></text> <path class=nj-charts-clang d="M362.6 434 h0.5 v12 h-0.5 Z"><title>JSON_USE_GLOBAL_UDLS=0, model TU (Apple clang): 0 %</title></path> <text class=nj-charts-val x=367.6 y=444.5>0 %</text> <path class=nj-charts-gcc d="M362.6 448 H362.6 Q358.66 448 358.66 451.94 V456.06 Q358.66 460 362.6 460 H362.6 Z"><title>JSON_USE_GLOBAL_UDLS=0, model TU (G&#8203;CC 16): &#8722;1 %</title></path> <text class=nj-charts-val x=367.6 y=458.5>&#8722;1 %</text> <line class=nj-charts-zero x1=362.6 y1=58 x2=362.6 y2=472 /> </svg></p> </div> <p class=nj-charts-caption>Change in compile time at <code>-O0</code> against the default configuration of the same translation unit, taken from the tables below (medians of nine runs, see above). * computed from the milliseconds in <a href=#options-without-effect-on-compile-times>Options without effect on compile times</a>.</p> <h2 id=include-json_fwdhpp-in-headers>Include <code>json_fwd.hpp</code> in headers<a class=headerlink href=#include-json_fwdhpp-in-headers title="Permanent link">&para;</a></h2> <p>Header files that only need to <em>name</em> the <code>json</code> type — for function declarations, members held by pointer or reference, or friend declarations — can include <code>&lt;nlohmann/json_fwd.hpp&gt;</code> instead of <code>&lt;nlohmann/json.hpp&gt;</code>. It only forward-declares <code>basic_json</code>, <code>json_pointer</code>, <code>adl_serializer</code>, and <code>ordered_map</code>, and defines the aliases <code>json</code> and <code>ordered_json</code>. The translation units that actually use the values then include <code>&lt;nlohmann/json.hpp&gt;</code>.</p> <div class=highlight><span class=filename>person.hpp</span><pre><span></span><code><span class=cp>#pragma once</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_fwd.hpp&gt;</span>
<span class=k>struct</span><span class=w> </span><span class=nc>person</span><span class=p>;</span>
<span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>);</span>
<span class=kt>void</span><span class=w> </span><span class=nf>from_json</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>);</span>
</code></pre></div> <div class=highlight><span class=filename>person.cpp</span><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>"person.hpp"</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=kt>void</span><span class=w> </span><span class=nf>to_json</span><span class=p>(</span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>)</span><span class=w> </span><span class=p>{</span><span class=w> </span><span class=cm>/* ... */</span><span class=w> </span><span class=p>}</span>
<span class=kt>void</span><span class=w> </span><span class=nf>from_json</span><span class=p>(</span><span class=k>const</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=o>&amp;</span><span class=w> </span><span class=n>j</span><span class=p>,</span><span class=w> </span><span class=n>person</span><span class=o>&amp;</span><span class=w> </span><span class=n>p</span><span class=p>)</span><span class=w> </span><span class=p>{</span><span class=w> </span><span class=cm>/* ... */</span><span class=w> </span><span class=p>}</span>
</code></pre></div> <table> <thead> <tr> <th>Compiler</th> <th style="text-align: right;"><code>json.hpp</code> (<code>-O0</code>)</th> <th style="text-align: right;"><code>json_fwd.hpp</code> (<code>-O0</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td style="text-align: right;">868 ms</td> <td style="text-align: right;">332 ms</td> <td style="text-align: right;">−62%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td style="text-align: right;">1164 ms</td> <td style="text-align: right;">210 ms</td> <td style="text-align: right;">−82%</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time of the header-only translation unit at <code>-O0</code> with each header, as the median wall-clock time of nine runs (see "Measurements" above). A negative change means a faster build.</p> <p>This is the most effective option, because it avoids the full header in every translation unit that includes <em>your</em> headers.</p> <h2 id=opt-out-of-the-automatic-user-defined-string-literals>Opt out of the automatic user-defined string literals<a class=headerlink href=#opt-out-of-the-automatic-user-defined-string-literals title="Permanent link">&para;</a></h2> <p>The user-defined string literals <a href=../../api/operator_literal_json/ ><code>operator""_json</code></a> and <a href=../../api/operator_literal_json_pointer/ ><code>operator""_json_pointer</code></a> are ordinary inline functions whose bodies call the parser. As <code>&lt;nlohmann/json.hpp&gt;</code> includes them by default, every translation unit instantiates the parser, even if it never parses anything itself.</p> <p>Define <a href=../../api/macros/json_no_automatic_udls/ ><code>JSON_NO_AUTOMATIC_UDLS</code></a> for the whole project and include <code>&lt;nlohmann/json_literals.hpp&gt;</code> instead of <code>&lt;nlohmann/json.hpp&gt;</code> in the files that use the literals (it includes <code>&lt;nlohmann/json.hpp&gt;</code> itself):</p> <div class=highlight><pre><span></span><code><span class=nb>target_compile_definitions</span><span class=p>(</span><span class=s>my_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>JSON_NO_AUTOMATIC_UDLS</span><span class=p>)</span>
</code></pre></div> <div class=highlight><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json_literals.hpp&gt;</span><span class=w> </span><span class=c1>// only where "..."_json is used; includes &lt;nlohmann/json.hpp&gt;</span>
</code></pre></div> <p>The saving applies to translation units that do not parse <abbr title="JavaScript Object Notation">JSON</abbr>, for example ones that define types and their conversions or only pass <code>json</code> values around:</p> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;">Default (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;"><code>JSON_NO_AUTOMATIC_UDLS</code> (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>model</td> <td style="text-align: right;">1051 ms / 1300 ms</td> <td style="text-align: right;">935 ms / 1170 ms</td> <td style="text-align: right;">−11% / −10%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>model</td> <td style="text-align: right;">1801 ms / 2106 ms</td> <td style="text-align: right;">1598 ms / 1983 ms</td> <td style="text-align: right;">−11% / −6%</td> </tr> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1157 ms / 2016 ms</td> <td style="text-align: right;">1146 ms / 2006 ms</td> <td style="text-align: right;">−1% / 0%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2529 ms / 4087 ms</td> <td style="text-align: right;">2484 ms / 4059 ms</td> <td style="text-align: right;">−2% / −1%</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time of the model and parsing translation units without and with <code>JSON_NO_AUTOMATIC_UDLS</code>, at <code>-O0</code> and <code>-O2</code>.</p> <p>The model translation unit saves about a tenth. Translation units that parse anyway instantiate the parser regardless and see no difference.</p> <h2 id=instantiate-basic_json-once>Instantiate <code>basic_json</code> once<a class=headerlink href=#instantiate-basic_json-once title="Permanent link">&para;</a></h2> <p>Each translation unit instantiates the member functions of <code>nlohmann::json</code> it uses. An explicit instantiation declaration tells the compiler that the non-template members are instantiated elsewhere, so it can skip them:</p> <div class=highlight><span class=filename>json_instance.hpp</span><pre><span></span><code><span class=cp>#pragma once</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=k>extern</span><span class=w> </span><span class=k>template</span><span class=w> </span><span class=k>class</span><span class=w> </span><span class=nc>nlohmann</span><span class=o>::</span><span class=n>basic_json</span><span class=o>&lt;&gt;</span><span class=p>;</span>
</code></pre></div> <div class=highlight><span class=filename>json_instance.cpp</span><pre><span></span><code><span class=cp>#include</span><span class=w> </span><span class=cpf>"json_instance.hpp"</span>
<span class=k>template</span><span class=w> </span><span class=k>class</span><span class=w> </span><span class=nc>nlohmann</span><span class=o>::</span><span class=n>basic_json</span><span class=o>&lt;&gt;</span><span class=p>;</span>
</code></pre></div> <p>Include <code>json_instance.hpp</code> instead of <code>&lt;nlohmann/json.hpp&gt;</code> and compile and link <code>json_instance.cpp</code> once.</p> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;">Default (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;"><code>extern template</code> (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1157 ms / 2016 ms</td> <td style="text-align: right;">1071 ms / 1844 ms</td> <td style="text-align: right;">−7% / −9%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2529 ms / 4087 ms</td> <td style="text-align: right;">1994 ms / 3190 ms</td> <td style="text-align: right;">−21% / −22%</td> </tr> <tr> <td>Apple clang</td> <td><code>json_instance.cpp</code></td> <td style="text-align: right;">—</td> <td style="text-align: right;">2573 ms / 6221 ms</td> <td style="text-align: right;">—</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td><code>json_instance.cpp</code></td> <td style="text-align: right;">—</td> <td style="text-align: right;">6489 ms / 13759 ms</td> <td style="text-align: right;">—</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time of the parsing translation unit without and with the <code>extern template</code> declaration, at <code>-O0</code> and <code>-O2</code>. The <code>json_instance.cpp</code> rows are the one-off cost of the translation unit that holds the instantiation.</p> <p>Notes:</p> <ul> <li>The saving grows with the number of translation units that use <code>json</code>, while the instantiation translation unit is compiled only once (and is rarely recompiled, as it does not depend on your code).</li> <li>Member function templates (such as <code>get&lt;T&gt;()</code>, <code>parse(InputType&amp;&amp;)</code>, or <code>value(key, default)</code>) are not covered by the explicit instantiation and are still instantiated where they are used.</li> <li>The declaration covers exactly <code>nlohmann::json</code>. Add the same lines for <code>nlohmann::ordered_json</code> (<code>nlohmann::basic_json&lt;nlohmann::ordered_map&gt;</code>) or your own <code>basic_json</code> specializations if you use them.</li> </ul> <h2 id=switch-off-filesystem-support>Switch off filesystem support<a class=headerlink href=#switch-off-filesystem-support title="Permanent link">&para;</a></h2> <p>With C++17, the library includes <code>&lt;filesystem&gt;</code> to provide conversions from and to <code>std::filesystem::path</code> (see <a href=../../api/macros/json_has_filesystem/ ><code>JSON_HAS_FILESYSTEM</code></a>). Parsing <code>&lt;filesystem&gt;</code> is a fixed cost in every translation unit, and it also pulls in <code>&lt;iomanip&gt;</code>, <code>&lt;istream&gt;</code>, and <code>&lt;ostream&gt;</code> (and, with <abbr title="GNU Compiler Collection">GCC</abbr>'s libstdc++, <code>&lt;sstream&gt;</code>). If you do not convert paths, switch the detection off for the whole project:</p> <div class=highlight><pre><span></span><code><span class=nb>target_compile_definitions</span><span class=p>(</span><span class=s>my_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>JSON_HAS_FILESYSTEM=0</span><span class=w> </span><span class=s>JSON_HAS_EXPERIMENTAL_FILESYSTEM=0</span><span class=p>)</span>
</code></pre></div> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;">Default (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Filesystem off (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>model</td> <td style="text-align: right;">1051 ms / 1300 ms</td> <td style="text-align: right;">998 ms / 1257 ms</td> <td style="text-align: right;">−5% / −3%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>model</td> <td style="text-align: right;">1801 ms / 2106 ms</td> <td style="text-align: right;">1636 ms / 2008 ms</td> <td style="text-align: right;">−9% / −5%</td> </tr> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1157 ms / 2016 ms</td> <td style="text-align: right;">1107 ms / 1971 ms</td> <td style="text-align: right;">−4% / −2%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2529 ms / 4087 ms</td> <td style="text-align: right;">2405 ms / 4029 ms</td> <td style="text-align: right;">−5% / −1%</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time with <code>JSON_HAS_FILESYSTEM=0</code> and <code>JSON_HAS_EXPERIMENTAL_FILESYSTEM=0</code> against the default configuration, at <code>-O0</code> and <code>-O2</code>.</p> <p>Only with filesystem support switched off does <a href=../../api/macros/json_no_io/ ><code>JSON_NO_IO</code></a> remove the stream headers from the translation unit, so the two macros save most together:</p> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;">Default (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Filesystem off and <code>JSON_NO_IO</code> (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>model</td> <td style="text-align: right;">1051 ms / 1300 ms</td> <td style="text-align: right;">969 ms / 1219 ms</td> <td style="text-align: right;">−8% / −6%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>model</td> <td style="text-align: right;">1801 ms / 2106 ms</td> <td style="text-align: right;">1605 ms / 1982 ms</td> <td style="text-align: right;">−11% / −6%</td> </tr> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1157 ms / 2016 ms</td> <td style="text-align: right;">1083 ms / 1947 ms</td> <td style="text-align: right;">−6% / −3%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2529 ms / 4087 ms</td> <td style="text-align: right;">2384 ms / 3972 ms</td> <td style="text-align: right;">−6% / −3%</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time with filesystem support switched off and <code>JSON_NO_IO</code> defined, against the default configuration, at <code>-O0</code> and <code>-O2</code>.</p> <p>The trade-off: the library's own <code>to_json</code>/<code>from_json</code> overloads for <code>std::filesystem::path</code> (which store the path as <abbr title="Unicode Transformation Format">UTF</abbr>-8) are removed. In a test with both compilers on macOS, paths still converted through their implicit conversion from and to <code>std::string</code>; whether that fallback exists depends on the platform's native path string type (<code>std::wstring</code> on Windows), so check code that converts paths. <code>JSON_NO_IO</code> additionally removes all stream functions (see <a href=#options-without-effect-on-compile-times>Options without effect</a>).</p> <h2 id=use-c20-modules>Use C++20 modules<a class=headerlink href=#use-c20-modules title="Permanent link">&para;</a></h2> <p>With a toolchain that supports named modules, <code>import nlohmann.json;</code> compiles the library once into a module and avoids parsing the header in every translation unit. See <a href=../../features/modules/ >Modules</a> for requirements and known issues. Module support is experimental and currently depends heavily on the compiler version.</p> <div class=nj-fig-wrap> <p><svg class="nj-fig nj-charts nj-charts--compile" viewbox="0 0 440 282" role=img aria-labelledby="nj-charts-mod nj-charts-mod-d" xmlns=http://www.w3.org/2000/svg> <title id=nj-charts-mod>Compile time per translation unit with import nlohmann.json at -O0, and the one-off cost of the module</title> <desc id=nj-charts-mod-d>Horizontal bars, negative is faster, medians of nine runs, -std=c++20 for both. model TU, Apple clang: -48 % (1311 ms to 680 ms); model TU, G&#8203;CC 16: -47 % (2156 ms to 1153 ms); parsing TU, Apple clang: -42 % (1387 ms to 800 ms); parsing TU, G&#8203;CC 16: -36 % (2838 ms to 1810 ms); one-off build, Apple clang: 1630 ms; one-off build, G&#8203;CC 16: 2538 ms.</desc> <rect class=nj-charts-clang x=8 y=10 width=12 height=12 rx=3 /> <text class=nj-charts-leg x=26 y=20.5>Apple clang</text> <rect class=nj-charts-gcc x=126 y=10 width=12 height=12 rx=3 /> <text class=nj-charts-leg x=144 y=20.5>G&#8203;CC 16</text> <line class=nj-charts-grid x1=68.6667 y1=58 x2=68.6667 y2=160 /> <text class=nj-charts-tick x=68.6667 y=176>&#8722;50 %</text> <line class=nj-charts-grid x1=220.333 y1=58 x2=220.333 y2=160 /> <text class=nj-charts-tick x=220.333 y=176>&#8722;25 %</text> <text class=nj-charts-tick x=372 y=176>0 %</text> <text class="nj-charts-tick nj-charts-tick--l" x=8 y=194>&#8592; faster per TU</text> <text class=nj-charts-rowlabel x=8 y=62>model TU<tspan class=nj-charts-sub> &#183; import nlohmann.json</tspan></text> <path class=nj-charts-clang d="M372 70 H84.8 Q80.8 70 80.8 74 V78 Q80.8 82 84.8 82 H372 Z"><title>model TU, Apple clang: 1311 ms by default, 680 ms import nlohmann.json (&#8722;48 %)</title></path> <text class=nj-charts-val x=377 y=80.5>&#8722;48 %</text> <path class=nj-charts-gcc d="M372 84 H90.8667 Q86.8667 84 86.8667 88 V92 Q86.8667 96 90.8667 96 H372 Z"><title>model TU, G&#8203;CC 16: 2156 ms by default, 1153 ms import nlohmann.json (&#8722;47 %)</title></path> <text class=nj-charts-val x=377 y=94.5>&#8722;47 %</text> <text class=nj-charts-rowlabel x=8 y=114>parsing TU<tspan class=nj-charts-sub> &#183; import nlohmann.json</tspan></text> <path class=nj-charts-clang d="M372 122 H121.2 Q117.2 122 117.2 126 V130 Q117.2 134 121.2 134 H372 Z"><title>parsing TU, Apple clang: 1387 ms by default, 800 ms import nlohmann.json (&#8722;42 %)</title></path> <text class=nj-charts-val x=377 y=132.5>&#8722;42 %</text> <path class=nj-charts-gcc d="M372 136 H157.6 Q153.6 136 153.6 140 V144 Q153.6 148 157.6 148 H372 Z"><title>parsing TU, G&#8203;CC 16: 2838 ms by default, 1810 ms import nlohmann.json (&#8722;36 %)</title></path> <text class=nj-charts-val x=377 y=146.5>&#8722;36 %</text> <line class=nj-charts-zero x1=372 y1=58 x2=372 y2=160 /> <text class=nj-charts-rowlabel x=8 y=222>One-off cost<tspan class=nj-charts-sub> &#183; built once, reused by every TU</tspan></text> <rect class=nj-charts-clang x=8 y=232.5 width=10 height=10 rx=2.5 /> <text class=nj-charts-val x=24 y=242>Apple clang: 1630 ms once, saves 587 to 631 ms per TU</text> <rect class=nj-charts-gcc x=8 y=252.5 width=10 height=10 rx=2.5 /> <text class=nj-charts-val x=24 y=262>G&#8203;CC 16: 2538 ms once, saves 1003 to 1028 ms per TU</text> </svg></p> </div> <p class=nj-caption>Change in compile time per translation unit at <code>-O0</code> when <code>#include &lt;nlohmann/json.hpp&gt;</code> is replaced by <code>import nlohmann.json;</code>, both with <code>-std=c++20</code>, and the one-off cost of building the module, taken from the table below.</p> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;"><code>#include</code> (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;"><code>import nlohmann.json;</code> (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>model</td> <td style="text-align: right;">1311 ms / 1597 ms</td> <td style="text-align: right;">680 ms / 914 ms</td> <td style="text-align: right;">−48% / −43%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>model</td> <td style="text-align: right;">2156 ms / 2588 ms</td> <td style="text-align: right;">1153 ms / 1580 ms</td> <td style="text-align: right;">−47% / −39%</td> </tr> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1387 ms / 2319 ms</td> <td style="text-align: right;">800 ms / 1676 ms</td> <td style="text-align: right;">−42% / −28%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2838 ms / 4520 ms</td> <td style="text-align: right;">1810 ms / 3476 ms</td> <td style="text-align: right;">−36% / −23%</td> </tr> <tr> <td>Apple clang</td> <td><code>json.cppm</code> (module)</td> <td style="text-align: right;">—</td> <td style="text-align: right;">1630 ms / 1642 ms</td> <td style="text-align: right;">—</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td><code>json.cppm</code> (module)</td> <td style="text-align: right;">—</td> <td style="text-align: right;">2538 ms / 2547 ms</td> <td style="text-align: right;">—</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time with <code>#include &lt;nlohmann/json.hpp&gt;</code> and with <code>import nlohmann.json;</code>, both with <code>-std=c++20</code>, at <code>-O0</code> and <code>-O2</code>. The <code>json.cppm</code> rows are the one-off cost of building the module.</p> <p>Both columns use <code>-std=c++20</code>; with <code>-std=c++17</code>, the <code>#include</code> baseline is 17% to 20% faster (see the next section). The module is built once per set of compiler flags and pays for itself from about the third translation unit that imports it. Notes from the measurement:</p> <ul> <li>Apple clang only accepts the module declarations with <code>-fcxx-modules</code>; without it, <code>module;</code> is a syntax error.</li> <li><abbr title="GNU Compiler Collection">GCC</abbr> 16 warns with <code>-Wexpose-global-module-tu-local</code> about internal constants of the library when building the module. With <abbr title="GNU Compiler Collection">GCC</abbr> 16.2, including <code>&lt;string&gt;</code> and <code>&lt;vector&gt;</code> before <code>import nlohmann.json;</code> works, but including them after it fails with redefinition errors (<a href="https://github.com/nlohmann/json/issues/5103">#5103</a>).</li> </ul> <details class=example> <summary>How these numbers were measured</summary> <p>The model and parsing translation units are the ones listed at the top of this page, with <code>import nlohmann.json;</code> in place of <code>#include &lt;nlohmann/json.hpp&gt;</code> (after <code>#include &lt;string&gt;</code> and <code>#include &lt;vector&gt;</code>). Same method as for the other tables, with <code>-std=c++20</code>.</p> <div class=highlight><pre><span></span><code><span class=c1># Apple clang: build the module once, then import it</span>
clang++<span class=w> </span>-std<span class=o>=</span>c++20<span class=w> </span>-fcxx-modules<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-c<span class=w> </span>-x<span class=w> </span>c++-module<span class=w> </span>src/modules/json.cppm<span class=w> </span><span class=se>\</span>
<span class=w> </span>-fmodule-output<span class=o>=</span>nlohmann.json.pcm<span class=w> </span>-o<span class=w> </span>json_mod.o
clang++<span class=w> </span>-std<span class=o>=</span>c++20<span class=w> </span>-fcxx-modules<span class=w> </span>-O0<span class=w> </span>-fmodule-file<span class=o>=</span>nlohmann.json<span class=o>=</span>nlohmann.json.pcm<span class=w> </span>-c<span class=w> </span>model.cpp
<span class=c1># GCC 16 (Homebrew on macOS): writes gcm.cache/nlohmann.json.gcm, found by the importing translation unit</span>
g++-16<span class=w> </span>--sysroot<span class=o>=</span><span class=k>$(</span>xcrun<span class=w> </span>--show-sdk-path<span class=k>)</span><span class=w> </span>-std<span class=o>=</span>c++20<span class=w> </span>-fmodules<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-c<span class=w> </span>src/modules/json.cppm<span class=w> </span><span class=se>\</span>
<span class=w> </span>-o<span class=w> </span>json_mod.o
g++-16<span class=w> </span>--sysroot<span class=o>=</span><span class=k>$(</span>xcrun<span class=w> </span>--show-sdk-path<span class=k>)</span><span class=w> </span>-std<span class=o>=</span>c++20<span class=w> </span>-fmodules<span class=w> </span>-O0<span class=w> </span>-c<span class=w> </span>model.cpp
</code></pre></div> <p>Link <code>json_mod.o</code> into the program.</p> </details> <h2 id=use-precompiled-headers>Use precompiled headers<a class=headerlink href=#use-precompiled-headers title="Permanent link">&para;</a></h2> <p>Build systems can precompile <code>&lt;nlohmann/json.hpp&gt;</code> together with other stable headers, for example with CMake's <a href="https://cmake.org/cmake/help/latest/command/target_precompile_headers.html"><code>target_precompile_headers</code></a>:</p> <div class=highlight><pre><span></span><code><span class=nb>target_precompile_headers</span><span class=p>(</span><span class=s>my_target</span><span class=w> </span><span class=s>PRIVATE</span><span class=w> </span><span class=s>&lt;nlohmann/json.hpp&gt;</span><span class=p>)</span>
</code></pre></div> <p>This removes the cost of parsing the header, but not of instantiating templates in each translation unit, so it combines well with the options above.</p> <div class=nj-fig-wrap> <p><svg class="nj-fig nj-charts nj-charts--compile" viewbox="0 0 440 282" role=img aria-labelledby="nj-charts-pch nj-charts-pch-d" xmlns=http://www.w3.org/2000/svg> <title id=nj-charts-pch>Compile time per translation unit with a precompiled json.hpp at -O0, and the one-off cost of the PCH</title> <desc id=nj-charts-pch-d>Horizontal bars, negative is faster, medians of nine runs, -std=c++17. model TU, Apple clang: -43 % (1045 ms to 594 ms); model TU, G&#8203;CC 16: -41 % (1789 ms to 1060 ms); parsing TU, Apple clang: -38 % (1148 ms to 714 ms); parsing TU, G&#8203;CC 16: -25 % (2498 ms to 1884 ms); one-off build, Apple clang: 771 ms; one-off build, G&#8203;CC 16: 2254 ms.</desc> <rect class=nj-charts-clang x=8 y=10 width=12 height=12 rx=3 /> <text class=nj-charts-leg x=26 y=20.5>Apple clang</text> <rect class=nj-charts-gcc x=126 y=10 width=12 height=12 rx=3 /> <text class=nj-charts-leg x=144 y=20.5>G&#8203;CC 16</text> <line class=nj-charts-grid x1=68.6667 y1=58 x2=68.6667 y2=160 /> <text class=nj-charts-tick x=68.6667 y=176>&#8722;50 %</text> <line class=nj-charts-grid x1=220.333 y1=58 x2=220.333 y2=160 /> <text class=nj-charts-tick x=220.333 y=176>&#8722;25 %</text> <text class=nj-charts-tick x=372 y=176>0 %</text> <text class="nj-charts-tick nj-charts-tick--l" x=8 y=194>&#8592; faster per TU</text> <text class=nj-charts-rowlabel x=8 y=62>model TU<tspan class=nj-charts-sub> &#183; with PCH</tspan></text> <path class=nj-charts-clang d="M372 70 H115.133 Q111.133 70 111.133 74 V78 Q111.133 82 115.133 82 H372 Z"><title>model TU, Apple clang: 1045 ms by default, 594 ms with PCH (&#8722;43 %)</title></path> <text class=nj-charts-val x=377 y=80.5>&#8722;43 %</text> <path class=nj-charts-gcc d="M372 84 H127.267 Q123.267 84 123.267 88 V92 Q123.267 96 127.267 96 H372 Z"><title>model TU, G&#8203;CC 16: 1789 ms by default, 1060 ms with PCH (&#8722;41 %)</title></path> <text class=nj-charts-val x=377 y=94.5>&#8722;41 %</text> <text class=nj-charts-rowlabel x=8 y=114>parsing TU<tspan class=nj-charts-sub> &#183; with PCH</tspan></text> <path class=nj-charts-clang d="M372 122 H145.467 Q141.467 122 141.467 126 V130 Q141.467 134 145.467 134 H372 Z"><title>parsing TU, Apple clang: 1148 ms by default, 714 ms with PCH (&#8722;38 %)</title></path> <text class=nj-charts-val x=377 y=132.5>&#8722;38 %</text> <path class=nj-charts-gcc d="M372 136 H224.333 Q220.333 136 220.333 140 V144 Q220.333 148 224.333 148 H372 Z"><title>parsing TU, G&#8203;CC 16: 2498 ms by default, 1884 ms with PCH (&#8722;25 %)</title></path> <text class=nj-charts-val x=377 y=146.5>&#8722;25 %</text> <line class=nj-charts-zero x1=372 y1=58 x2=372 y2=160 /> <text class=nj-charts-rowlabel x=8 y=222>One-off cost<tspan class=nj-charts-sub> &#183; built once, reused by every TU</tspan></text> <rect class=nj-charts-clang x=8 y=232.5 width=10 height=10 rx=2.5 /> <text class=nj-charts-val x=24 y=242>Apple clang: 771 ms once, saves 434 to 451 ms per TU</text> <rect class=nj-charts-gcc x=8 y=252.5 width=10 height=10 rx=2.5 /> <text class=nj-charts-val x=24 y=262>G&#8203;CC 16: 2254 ms once, saves 614 to 729 ms per TU</text> </svg></p> </div> <p class=nj-caption>Change in compile time per translation unit at <code>-O0</code> with a precompiled <code>&lt;nlohmann/json.hpp&gt;</code> (<code>-std=c++17</code>), and the one-off cost of building the precompiled header, taken from the table below.</p> <table> <thead> <tr> <th>Compiler</th> <th>Translation unit</th> <th style="text-align: right;">Default (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">With PCH (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;">Change</th> </tr> </thead> <tbody> <tr> <td>Apple clang</td> <td>model</td> <td style="text-align: right;">1045 ms / 1295 ms</td> <td style="text-align: right;">594 ms / 842 ms</td> <td style="text-align: right;">−43% / −35%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>model</td> <td style="text-align: right;">1789 ms / 2101 ms</td> <td style="text-align: right;">1060 ms / 1376 ms</td> <td style="text-align: right;">−41% / −35%</td> </tr> <tr> <td>Apple clang</td> <td>parsing</td> <td style="text-align: right;">1148 ms / 2008 ms</td> <td style="text-align: right;">714 ms / 1584 ms</td> <td style="text-align: right;">−38% / −21%</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>parsing</td> <td style="text-align: right;">2498 ms / 4075 ms</td> <td style="text-align: right;">1884 ms / 3452 ms</td> <td style="text-align: right;">−25% / −15%</td> </tr> <tr> <td>Apple clang</td> <td>building the PCH</td> <td style="text-align: right;">—</td> <td style="text-align: right;">771 ms / 760 ms</td> <td style="text-align: right;">—</td> </tr> <tr> <td><abbr title="GNU Compiler Collection">GCC</abbr> 16</td> <td>building the PCH</td> <td style="text-align: right;">—</td> <td style="text-align: right;">2254 ms / 2218 ms</td> <td style="text-align: right;">—</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time without and with a precompiled <code>&lt;nlohmann/json.hpp&gt;</code>, at <code>-O0</code> and <code>-O2</code>. The last two rows are the one-off cost of building the precompiled header.</p> <p>The saving is largest in translation units that instantiate little, and the PCH pays for itself from the second (Apple clang) or fourth (<abbr title="GNU Compiler Collection">GCC</abbr>) translation unit. A precompiled header only works with the flags it was built with: <abbr title="GNU Compiler Collection">GCC</abbr> silently ignores a mismatching <code>.gch</code> file (for example one built with another <code>-O</code> level) unless <code>-Winvalid-pch</code> is given.</p> <details class=example> <summary>How these numbers were measured</summary> <p><code>pch.hpp</code> contains only <code>#include &lt;nlohmann/json.hpp&gt;</code>; the translation units are the ones listed at the top of this page.</p> <div class=highlight><pre><span></span><code><span class=c1># Apple clang</span>
clang++<span class=w> </span>-std<span class=o>=</span>c++17<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-x<span class=w> </span>c++-header<span class=w> </span>pch.hpp<span class=w> </span>-o<span class=w> </span>pch.hpp.pch
clang++<span class=w> </span>-std<span class=o>=</span>c++17<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-include-pch<span class=w> </span>pch.hpp.pch<span class=w> </span>-include<span class=w> </span>pch.hpp<span class=w> </span>-c<span class=w> </span>model.cpp
<span class=c1># GCC 16 (Homebrew on macOS): pch.hpp.gch next to pch.hpp is picked up by -include pch.hpp</span>
g++-16<span class=w> </span>--sysroot<span class=o>=</span><span class=k>$(</span>xcrun<span class=w> </span>--show-sdk-path<span class=k>)</span><span class=w> </span>-std<span class=o>=</span>c++17<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-x<span class=w> </span>c++-header<span class=w> </span>pch.hpp<span class=w> </span>-o<span class=w> </span>pch.hpp.gch
g++-16<span class=w> </span>--sysroot<span class=o>=</span><span class=k>$(</span>xcrun<span class=w> </span>--show-sdk-path<span class=k>)</span><span class=w> </span>-std<span class=o>=</span>c++17<span class=w> </span>-O0<span class=w> </span>-I<span class=w> </span>single_include<span class=w> </span>-include<span class=w> </span>pch.hpp<span class=w> </span>-Winvalid-pch<span class=w> </span>-c<span class=w> </span>model.cpp
</code></pre></div> </details> <h2 id=options-without-effect-on-compile-times>Options without effect on compile times<a class=headerlink href=#options-without-effect-on-compile-times title="Permanent link">&para;</a></h2> <p>Some configuration macros change what the library declares, but do not measurably change compile times:</p> <table> <thead> <tr> <th>Macro</th> <th style="text-align: right;">Apple clang, model (<code>-O0</code> / <code>-O2</code>)</th> <th style="text-align: right;"><abbr title="GNU Compiler Collection">GCC</abbr> 16, model (<code>-O0</code> / <code>-O2</code>)</th> </tr> </thead> <tbody> <tr> <td>default</td> <td style="text-align: right;">1051 ms / 1300 ms</td> <td style="text-align: right;">1801 ms / 2106 ms</td> </tr> <tr> <td><a href=../../api/macros/json_no_io/ ><code>JSON_NO_IO</code></a></td> <td style="text-align: right;">1034 ms / 1288 ms</td> <td style="text-align: right;">1756 ms / 2087 ms</td> </tr> <tr> <td><a href=../../api/macros/json_use_global_udls/ ><code>JSON_USE_GLOBAL_UDLS</code></a><code>=0</code></td> <td style="text-align: right;">1055 ms / 1298 ms</td> <td style="text-align: right;">1783 ms / 2109 ms</td> </tr> </tbody> </table> <p class=nj-table-caption>Compile time of the model translation unit with each macro defined; the first row is the default configuration for comparison.</p> <p><code>JSON_NO_IO</code> removes the library's stream functions and its <code>#include</code>s of <code>&lt;istream&gt;</code> and <code>&lt;ostream&gt;</code>, but with the default C++17 settings <code>&lt;filesystem&gt;</code> includes these headers anyway (and with libc++, <code>&lt;vector&gt;</code> already includes <code>&lt;streambuf&gt;</code> via <code>&lt;locale&gt;</code>), so only a few hundred lines of the library's own stream code go away. It also does not change what the translation unit instantiates. On the parsing translation unit, the change is 0% / 0% (Apple clang) and −2% / 0% (<abbr title="GNU Compiler Collection">GCC</abbr>). To get a saving, combine it with <a href=#switch-off-filesystem-support>switching off filesystem support</a>.</p> <p><code>JSON_USE_GLOBAL_UDLS</code> only controls <em>where</em> the literals are declared; to avoid their cost, use <code>JSON_NO_AUTOMATIC_UDLS</code> instead.</p> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../api/macros/json_has_filesystem/ ><code>JSON_HAS_FILESYSTEM</code></a> - control the conversions from and to <code>std::filesystem::path</code></li> <li><a href=../../api/macros/json_no_automatic_udls/ ><code>JSON_NO_AUTOMATIC_UDLS</code></a> - do not include the user-defined string literals automatically</li> <li><a href=../../features/modules/ >Modules</a> - C++20 module support</li> <li><a href=../ >Header only</a> - including the library</li> <li><a href=../../api/macros/ >Macros</a> - reference of all macros</li> <li><a href=../../features/macros/ >Supported Macros</a> - overview of all configuration macros</li> <li><a href=../../features/performance/ >Performance</a> - 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