The macros are found here:
General guidelines are found here:
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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; #else typedef char * t_pointer; #endif
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 #endif
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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