Remove 32-bit limitation (#2388)

* Remove 32-bit limitation

* Fix build problems

* Add 32-bit disclaimer and fix MSVC x86 warnings

- Move 32-bit warning to top of README with strong disclaimer
- Add static_cast<size_t> to fix truncation warnings on 32-bit MSVC

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/test-32bit.yml

@@ -0,0 +1,36 @@
+name: 32-bit Build Test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  test-win32:
+    name: Windows 32-bit (MSVC x86)
+    runs-on: windows-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build (Win32)
+        shell: cmd
+        run: |
+          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" x86
+          cl /std:c++14 /EHsc /W4 /WX /c /Fo:NUL test\test_32bit_build.cpp
+
+  test-arm32:
+    name: ARM 32-bit (cross-compile)
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install cross compiler
+        run: sudo apt-get update && sudo apt-get install -y g++-arm-linux-gnueabihf
+      - name: Build (ARM 32-bit)
+        run: arm-linux-gnueabihf-g++ -std=c++11 -Wall -Wextra -Wno-psabi -Werror -c -o /dev/null test/test_32bit_build.cpp

.github/workflows/test.yaml

@@ -40,7 +40,7 @@ jobs:
           clang-format --version
           cd test && make style_check
 
-  build-error-check-on-32bit:
+  build-and-test-on-32bit:
     runs-on: ubuntu-latest
     if: >
       (github.event_name == 'push') ||
@@ -64,9 +64,8 @@ jobs:
             libssl-dev${{ matrix.config.arch_suffix }} libcurl4-openssl-dev${{ matrix.config.arch_suffix }} \
             zlib1g-dev${{ matrix.config.arch_suffix }} libbrotli-dev${{ matrix.config.arch_suffix }} \
             libzstd-dev${{ matrix.config.arch_suffix }}
-      - name: build and run tests (expect failure)
+      - name: build and run tests
         run: cd test && make test EXTRA_CXXFLAGS="${{ matrix.config.arch_flags }}"
-        continue-on-error: true
 
   ubuntu:
     runs-on: ubuntu-latest

CMakeLists.txt

@@ -173,9 +173,6 @@ if(CMAKE_SYSTEM_NAME MATCHES "Windows")
 		message(WARNING "The target is Windows but CMAKE_SYSTEM_VERSION is not set, the default system version is set to Windows 10.")
 	endif()
 endif()
-if(CMAKE_SIZEOF_VOID_P LESS 8)
-	message(WARNING "Pointer size ${CMAKE_SIZEOF_VOID_P} is not supported. Please use a 64-bit compiler.")
-endif()
 
 # Set some variables that are used in-tree and while building based on our options
 set(HTTPLIB_IS_COMPILED ${HTTPLIB_COMPILE})

README.md

@@ -10,6 +10,9 @@ Learn more in the [official documentation](https://yhirose.github.io/cpp-httplib
 > [!IMPORTANT]
 > This library uses 'blocking' socket I/O. If you are looking for a library with 'non-blocking' socket I/O, this is not the one that you want.
 
+> [!WARNING]
+> 32-bit platforms are **NOT supported**. Use at your own risk. The library may compile on 32-bit targets, but no security review has been conducted for 32-bit environments. Integer truncation and other 32-bit-specific issues may exist. **Security reports that only affect 32-bit platforms will be closed without action.** The maintainer does not have access to 32-bit environments for testing or fixing issues. CI includes basic compile checks only, not functional or security testing.
+
 ## Main Features
 
 - HTTP Server/Client

httplib.h

@@ -11,26 +11,6 @@
 #define CPPHTTPLIB_VERSION "0.37.0"
 #define CPPHTTPLIB_VERSION_NUM "0x002500"
 
-/*
- * Platform compatibility check
- */
-
-#if defined(_WIN32) && !defined(_WIN64)
-#if defined(_MSC_VER)
-#pragma message(                                                               \
-    "cpp-httplib doesn't support 32-bit Windows. Please use a 64-bit compiler.")
-#else
-#warning                                                                       \
-    "cpp-httplib doesn't support 32-bit Windows. Please use a 64-bit compiler."
-#endif
-#elif defined(__SIZEOF_POINTER__) && __SIZEOF_POINTER__ < 8
-#warning                                                                       \
-    "cpp-httplib doesn't support 32-bit platforms. Please use a 64-bit compiler."
-#elif defined(__SIZEOF_SIZE_T__) && __SIZEOF_SIZE_T__ < 8
-#warning                                                                       \
-    "cpp-httplib doesn't support platforms where size_t is less than 64 bits."
-#endif
-
 #ifdef _WIN32
 #if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
 #error                                                                         \
@@ -2801,7 +2781,7 @@ inline size_t get_header_value_u64(const Headers &headers,
   std::advance(it, static_cast<ssize_t>(id));
   if (it != rng.second) {
     if (is_numeric(it->second)) {
-      return std::strtoull(it->second.data(), nullptr, 10);
+      return static_cast<size_t>(std::strtoull(it->second.data(), nullptr, 10));
     } else {
       is_invalid_value = true;
     }
@@ -8241,7 +8221,8 @@ get_range_offset_and_length(Range r, size_t content_length) {
   assert(r.first <= r.second &&
          r.second < static_cast<ssize_t>(content_length));
   (void)(content_length);
-  return std::make_pair(r.first, static_cast<size_t>(r.second - r.first) + 1);
+  return std::make_pair(static_cast<size_t>(r.first),
+                        static_cast<size_t>(r.second - r.first) + 1);
 }
 
 inline std::string make_content_range_header_field(

test/test_32bit_build.cpp

@@ -0,0 +1,9 @@
+#include "../httplib.h"
+
+int main() {
+  httplib::Server svr;
+  httplib::Client cli("localhost", 8080);
+  (void)svr;
+  (void)cli;
+  return 0;
+}