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Pre-defined C/C++ Compiler Macros

The macros are found here:

General guidelines are found here:

Please send updates/corrections to predef-contribute.


C and C++ compilers automatically define certain macros that can be used to check for compiler or operating system features. This is useful when writing portable software.

These pages lists various pre-defined compiler macros that can be used to identify standards, compilers, operating systems, hardware architectures, and even basic run-time libraries at compile-time.

For example, if we want to use a generic or opaque pointer type, we use void pointers. However, ancient K&R compilers (from the time before the first ANSI C standard) do not support void pointers. Instead we can define our own type:

#if defined(__STDC__) || defined(__cplusplus) || defined(_MSC_EXTENSIONS)
typedef void * t_pointer;
typedef char * t_pointer;

Another example, Microsoft Visual C++ version 4.2 added a pragma to reduce compilation times by only including a file once (if _MSC_VER is not defined then it will evaluate to 0 (zero) — however, some compilers may complain about an undefined macro)

#if defined(_MSC_VER) && (_MSC_VER >= 1020)
#pragma once

The macros contained in these pages have been obtained through vendor documentation, the defines script, contributors, and third-party source code. No guarantee about the correctness of the macros is given.

An often-used alternative is Autoconf, which is a more powerful tool to examine various types of features, including compilation options. However, Autoconf is fairly Unix-centric, and requires a Unix layer on other platforms (e.g. Cygwin on Windows). Other alternatives are Buildtool, CMake, SCons, PMK, Jam, Ant, and Bakefile.


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Wiki: Architectures
Wiki: Compilers
Wiki: Endianness
Wiki: FeatureMacros
Wiki: Libraries
Wiki: OperatingSystems
Wiki: Standards
Wiki: VersionNormalization