Is there a preprocessor macro to detect C99 across platforms?

Question

C++ has a __cplusplus preprocessor define that lets you detect the version. Is there anything similar for C?

Preferably I'd like it to be portable across XCode, GCC, and Visual Studio versions.

score 11 · Accepted Answer · answered Oct 30 '13 at 05:24

11

As per article on Wikipedia on C99

A standard macro __STDC_VERSION__ is defined with value 199901L to indicate that C99 support is available

#if __STDC_VERSION__ >= 199901L
   /*C99*/
#else
  /*Not C99*/
#endif

answered Oct 30 '13 at 05:24

doptimusprime

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`__STDC_VERSION__` is maybe not defined in C90 compilers, you should check first if it is defined, without you can get a compiletime error. – 12431234123412341234123 Jan 03 '17 at 15:47
1

By default this macro do not work in MSVS C. The MSVS https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros states: `__STDC_VERSION__` Defined when compiled as C and one of the /std C11 or C17 options is specified. It expands to 201112L for /std:c11, and 201710L for /std:c17. – Jan Bergström Oct 18 '21 at 00:02

Yu Hao · Answer 2 · 2013-10-30T05:32:38.437

You can test the value of the macro __STDC_VERSION__ (note there are two underscores in the beginning and in the end), it should be larger than or equal to 199901L for C99 compatible platforms.

C11(ISO/IEC 9899:201x) §6.10.8.1 Mandatory macros

__STDC_VERSION__ The integer constant 201ymmL.

In the footnote:

This macro was not specified in ISO/IEC 9899:1990 and was specified as 199409L in ISO/IEC 9899/AMD1:1995 and as 199901L in ISO/IEC 9899:1999. The intention is that this will remain an integer constant of type long int that is increased with each revision of this International Standard.

Is there a preprocessor macro to detect C99 across platforms?

2 Answers2

C11(ISO/IEC 9899:201x) §6.10.8.1 Mandatory macros

Linked