How to find my current compiler's standard, like if it is C90, etc

c compiler-construction c99 c89

37,151

Solution 1

This is compiler dependent, I'm supposing you're using GCC. You could check your compiler defined macros using:

gcc -dM -E - < /dev/null

Check the manual about the flags, specially:

__STDC_VERSION__

This macro expands to the C Standard's version number, a long integer constant of the form yyyymmL where yyyy and mm are the year and month of the Standard version. This signifies which version of the C Standard the compiler conforms to. Like STDC, this is not necessarily accurate for the entire implementation, unless GNU CPP is being used with GCC.

The value 199409L signifies the 1989 C standard as amended in 1994, which is the current default; the value 199901L signifies the 1999 revision of the C standard. Support for the 1999 revision is not yet complete.

This macro is not defined if the -traditional-cpp option is used, nor when compiling C++ or Objective-C.

In this site you can find a lot of information about this. See the table present here.

Solution 2

You can also test this in your code using standard macros, for example (originally from sourceforge project of the same name):

#if defined(__STDC__)
# define PREDEF_STANDARD_C_1989
# if defined(__STDC_VERSION__)
#  define PREDEF_STANDARD_C_1990
#  if (__STDC_VERSION__ >= 199409L)
#   define PREDEF_STANDARD_C_1994
#  endif
#  if (__STDC_VERSION__ >= 199901L)
#   define PREDEF_STANDARD_C_1999
#  endif
#  if (__STDC_VERSION__ >= 201710L)
#   define PREDEF_STANDARD_C_2018
#  endif
# endif
#endif

If you want to check this from the command line you can pick one (e.g. c89) and check the return value from a minimal program:

echo -e "#ifdef __STDC__\n#error\n#endif"|gcc -xc -c - > /dev/null 2>&1; test $? -eq 0  || echo "c89

Solution 3

At compile time, check against preprocessor macro:

__ANSI__
__STDC__
__STDC_VERSION__ >= 199901L for c99

Solution 4

You probably have gcc, in which case you can specify the standard at compile-time, e.g.

$ gcc -Wall -std=c89 foo.c -o foo

or:

$ gcc -Wall -std=c99 foo.c -o foo

Type:

$ man gcc

for full details.

Solution 5

If your C compiler is gcc, you can use the -std option to specify which C standard to follow. The default is gnu89. There's no general system command to determine the standard for any given compiler. You'll need to check the documentation.

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