20 lines
2.2 KiB
Markdown
20 lines
2.2 KiB
Markdown
# Debugging
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This page collects the library's built-in debugger integrations and other debugging-related features. They are not linked from a single place elsewhere in the docs, so are collected here.
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## Visual Studio (natvis)
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The repository ships [`nlohmann_json.natvis`](https://github.com/nlohmann/json/blob/develop/nlohmann_json.natvis) at its root, a [Natvis](https://learn.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects) file that gives `json`/`ordered_json` values a friendly, key/value debugger view instead of showing raw internal fields, when debugging with the MSVC debug engine (`cppvsdbg`) in Visual Studio or VS Code.
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The checked-in visualizers cover namespace variants with zero, one, or two ABI tags. Configurations with three or more ABI tags are not covered and may show raw internal fields instead.
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Debug engines that wrap LLDB instead of the MSVC debug engine (for example, `codelldb` in VS Code) only have partial/experimental Natvis support, and commonly fall back to showing raw internal fields even with the `.natvis` file present. Switching to `cppvsdbg` where available, or checking your debug extension's own Natvis support/version, are the next things to try if this happens. There is currently no bundled LLDB-native pretty-printer script in this repository.
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## GDB
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The repository ships a [GDB Python pretty printer](https://github.com/nlohmann/json/tree/develop/tools/gdb_pretty_printer) under `tools/gdb_pretty_printer`, with its own usage instructions in that directory's `README.md`.
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## Extended exception diagnostics
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Defining [`JSON_DIAGNOSTICS`](https://json.nlohmann.me/api/macros/json_diagnostics/index.md) before including the library augments `type_error`/`out_of_range`-style exceptions with a JSON Pointer to the offending value, which can help pinpoint where in a large document a runtime error occurred. This only applies to exceptions thrown *after* a value exists (e.g. during element access); parse errors, which happen before any value exists to point at, are not covered by this mechanism -- see [Parsing and exceptions](https://json.nlohmann.me/features/parsing/parse_exceptions/index.md) for how parse errors report their own location instead.
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