Which version of C is supported by VS2019 compiler?

Question

How can I know which version of C is supported by the VS2019 compiler? I looked in the project C/C++ and Linker command lines and found no -std=Cxx flag. The following code compiles:

for (int i = index; i < nb_users - 1; i++) {
    users[i] = users[i + 1];
}

So I guess it's C99 according to this, but is there a way to check this somewhere in VS2019?

@chux It does not compile, "identifier is undefined". Sorry I'm new in C as you can tell. — evilmandarine, Sep 17 '19 at 09:01
`__STDC_VERSION__` wasn't allowed in C90, nor was declaring a variable inside a for loop `for (int i =...`. If you are a newbie, you are much better off throwing VS in the garbage and get a standard C compiler. For example Codeblocks with gcc/mingw compiler, it is a reasonably newbie-friendly Windows toolchain. — Lundin, Sep 17 '19 at 09:42
@supafly *It does not compile...* That means VS2019 is not a [C99-compliant compiler](https://port70.net/~nsz/c/c99/n1256.html#6.10.8). — Andrew Henle, Sep 17 '19 at 11:25

score 3 · Accepted Answer · answered Sep 16 '19 at 22:42

VS2019 supports ANSI C90 plus a few other features from a few later standards that are required in C++.

For example, you can tell that C99 is not fully supported in MSVC with this code, which will fail to compile:

int foo(int n, char *s)
{
    char s2[n];
    strcpy(s2, s);
    return !strcmp(s, s2);
}

This specific feature (variable-length arrays) is not supported in MSVC, while the feature you mentioned (for loop initial declaration) is.

chux - Reinstate Monica · Answer 2 · 2019-09-17T11:45:22.503

1

Which version of C is supported by VS2019 compiler?

At best, C 1989.

A compliant compiler to some C standard is identifiable via the values of __STDC__ __STDC_VERSION__.

#ifndef __STDC__
  printf("Does not ID itself as compliant to any C standard.\n");
#else
  printf("Compliant to some C standard\n");
  #ifndef __STDC_VERSION__
    printf("C 1989\n");
  #else 
    // Expected values of of 2019
    // 199409L
    // 199901L
    // 201112L
    // 201710L
    printf("C %ld\n", __STDC_VERSION__);
  #endif
#endif

I'd expect VS2019 to not identify itself compliant to any C standard or perhaps 1989.

__STDC__ Defined as 1 only when compiled as C and if the /Za compiler option is specified. Otherwise, undefined. Predefined macros

VS2019 not on this incomplete list of C compilers

edited Sep 17 '19 at 11:45

answered Sep 17 '19 at 11:34

chux - Reinstate Monica

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Indeed, it does not identify itself compliant to any C standard. The `/Za` link in your answer is helpful. – evilmandarine Sep 17 '19 at 21:17
Should it be `#elif __STDC__ == 1 printf("Compliant ...");` instead of `#else printf("Compliant ...");`? – pmor Apr 01 '21 at 16:05
@pmor Maybe after the `#ifndef __STDC__ printf("Does ...` could as `#elif __STDC__ != 1 printf("Not Compliant");` for a pedantic test - and then go on to the `#else printf("Compliant to some C standard\n");` – chux - Reinstate Monica Apr 01 '21 at 18:10
@chux-ReinstateMonica `__STDC__` is defined using "positive logic". Hence, I find logical to use "positive logic" as well: `#if __STDC__ == 1 /* compliant */ #else /* not defined OR defined to != 1 => not compliant */ #endif`. – pmor Apr 01 '21 at 22:26

Which version of C is supported by VS2019 compiler?

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