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Fix documentation of __STDC__ #5431

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ad233f6
Fix documentation of __STDC__
puetzk Jun 17, 2025
b51bd8f
Update predefined-macros.md
TylerMSFT Jun 18, 2025
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4 changes: 2 additions & 2 deletions docs/preprocessor/predefined-macros.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
title: "Predefined macros"
description: "Lists and describes the Microsoft C++ compiler predefined preprocessor macros."
ms.custom: "update_every_version"
ms.date: 06/11/2024
ms.date: 06/18/2025
f1_keywords: ["__ARM_ARCH", "_ATL_VER", "__ATOM__", "__AVX__", "__AVX2__", "__AVX512BW__", "__AVX512CD__", "__AVX512DQ__", "__AVX512F__", "__AVX512VL__", "_CHAR_UNSIGNED", "__CLR_VER", "_CONTROL_FLOW_GUARD", "__COUNTER__", "__cplusplus", "__cplusplus_cli", "__cplusplus_winrt", "_CPPRTTI", "_CPPUNWIND", "__DATE__", "_DEBUG", "_DLL", "__FILE__", "__FUNCDNAME__", "__FUNCSIG__", "__FUNCTION__", "_INTEGRAL_MAX_BITS", "_ISO_VOLATILE", "_KERNEL_MODE", "__LINE__", "_M_AMD64", "_M_ARM", "_M_ARM_ARMV7VE", "_M_ARM_FP", "_M_ARM64", "_M_CEE", "_M_CEE_PURE", "_M_CEE_SAFE", "_M_FP_EXCEPT", "_M_FP_FAST", "_M_FP_PRECISE", "_M_FP_STRICT", "_M_IX86", "_M_IX86_FP", "_M_X64", "_MANAGED", "_MFC_VER", "_MSC_BUILD", "_MSC_EXTENSIONS", "_MSC_FULL_VER", "_MSC_VER", "_MSVC_LANG", "__MSVC_RUNTIME_CHECKS", "_MT", "_NATIVE_WCHAR_T_DEFINED", "_NO_SIZED_DEALLOCATION", "_OPENMP", "_PREFAST_", "_RESUMABLE_FUNCTIONS_SUPPORTED", "_RTC_CONVERSION_CHECKS_ENABLED", "__SANITIZE_ADDRESS__", "__STDC__", "__STDC_HOSTED__", "__STDC_NO_ATOMICS__", "__STDC_NO_COMPLEX__", "__STDC_NO_THREADS__", "__STDC_NO_VLA__", "__STDC_VERSION__", "__STDCPP_DEFAULT_NEW_ALIGNMENT__", "__STDCPP_THREADS__", "__TIME__", "__TIMESTAMP__", "__VA_ARGS__", "_VC_NODEFAULTLIB", "_WCHAR_T_DEFINED", "_WIN32", "_WIN64", "_WINRT_DLL"]
helpviewer_keywords: ["__ARM_ARCH macro", "timestamps, preprocessor macro", "cl.exe compiler, version number", "version numbers, C/C++ compiler (cl.exe)", "macros, predefined C++", "preprocessor, macros", "predefined macros", "_ATL_VER macro", "__ATOM__ macro", "__AVX__ macro", "__AVX2__ macro", "__AVX512BW__ macro", "__AVX512CD__ macro", "__AVX512DQ__ macro", "__AVX512F__ macro", "__AVX512VL__ macro", "_CHAR_UNSIGNED macro", "__CLR_VER macro", "_CONTROL_FLOW_GUARD macro", "__COUNTER__ macro", "__cplusplus macro", "__cplusplus_cli macro", "__cplusplus_winrt macro", "_CPPRTTI macro", "_CPPUNWIND macro", "__DATE__ macro", "_DEBUG macro", "_DLL macro", "__FILE__ macro", "__FUNCDNAME__ macro", "__FUNCSIG__ macro", "__FUNCTION__ macro", "_INTEGRAL_MAX_BITS macro", "_ISO_VOLATILE macro", "_KERNEL_MODE macro", "__LINE__ macro", "_M_AMD64 macro", "_M_ARM macro", "_M_ARM_ARMV7VE macro", "_M_ARM_FP macro", "_M_ARM64 macro", "_M_ARM64EC macro", "_M_CEE macro", "_M_CEE_PURE macro", "_M_CEE_SAFE macro", "_M_FP_EXCEPT macro", "_M_FP_FAST macro", "_M_FP_PRECISE macro", "_M_FP_STRICT macro", "_M_IX86 macro", "_M_IX86_FP macro", "_M_X64 macro", "_MANAGED macro", "_MFC_VER macro", "_MSC_BUILD macro", "_MSC_EXTENSIONS macro", "_MSC_FULL_VER macro", "_MSC_VER macro", "_MSVC_LANG macro", "__MSVC_RUNTIME_CHECKS macro", "_MT macro", "_NATIVE_WCHAR_T_DEFINED macro", "_NO_SIZED_DEALLOCATION macro", "_OPENMP macro", "_PREFAST_ macro", "_RESUMABLE_FUNCTIONS_SUPPORTED macro", "_RTC_CONVERSION_CHECKS_ENABLED macro", "__SANITIZE_ADDRESS__ macro", "__STDC__ macro", "__STDC_HOSTED__ macro", "__STDC_NO_ATOMICS__ macro", "__STDC_NO_COMPLEX__ macro", "__STDC_NO_THREADS__ macro", "__STDC_NO_VLA__ macro", "__STDC_VERSION__ macro", "__STDCPP_DEFAULT_NEW_ALIGNMENT__", "__STDCPP_THREADS__ macro", "__TIME__ macro", "__TIMESTAMP__ macro", "__VA_ARGS__ macro", "_VC_NODEFAULTLIB macro", "_WCHAR_T_DEFINED macro", "_WIN32 macro", "_WIN64 macro", "_WINRT_DLL macro", "__func__ identifier"]
ms.assetid: 1cc5f70a-a225-469c-aed0-fe766238e23f
Expand Down Expand Up @@ -41,7 +41,7 @@ The compiler supports these predefined macros specified by the ISO C99, C11, C17

- `__LINE__` Defined as the integer line number in the current source file. The value of this macro can be changed by using a `#line` directive. The integral type of the value of `__LINE__` can vary depending on context. This macro is always defined.

- `__STDC__` Defined as 1 when compiled as C and if the [`/Za`](../build/reference/za-ze-disable-language-extensions.md) compiler option is specified. Starting in Visual Studio 2022 version 17.2, it's defined as 1 when compiled as C and if the [`/std:c11`](../build/reference/std-specify-language-standard-version.md) or [`/std:c17`](../build/reference/std-specify-language-standard-version.md) compiler option is specified. Otherwise, undefined.
- `__STDC__` Defined as 1 when compiled as C and if the [`/Za`](../build/reference/za-ze-disable-language-extensions.md) compiler option is specified. Starting in Visual Studio 2022 version 17.2, it's defined as 1 when compiled as C and if the [`/Zc:__STDC__`](../build/reference/zc-stdc.md) compiler option is specified. Otherwise, undefined.

- `__STDC_HOSTED__` Defined as 1 if the implementation is a *hosted implementation*, one that supports the entire required standard library. Otherwise, defined as 0.

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