Array with variable size in C in VS

Question

Under GCC 4.8.1

static int len = 10;
int main() {
    int a[len];
    return 0;
}

can compile success.

But compile will fail if changed like this:

static int len = 10;
int main() {
    static int a[len];
    return 0;
}

But in my Visual Studio, the former also can not compile success. How can I fix this problem? And is there a way to change latter one to make it compile success?

If you want to use Visual Studio, the obvious fix is to replace the VLAs by pointers and explicitly malloc the memory. In C99 they are really a rather minor conviencence and are easy enough to live without. — John Coleman, Apr 16 '16 at 10:50
@JohnColeman You're right, but I disagree with VLAs being "a minor convenience". In most implementations, they're segfaults waiting to happen, because they're essentially uncontrollable calls to `alloca()`. — , Apr 16 '16 at 11:16
@JohnColeman I don't know. The C11 rationale hasn't been published yet. Hurray, standards organisations. — , Apr 16 '16 at 11:33

score 1 · Accepted Answer · edited May 23 '17 at 11:59

1

The MSVC compiler only supports C90, it does not support C99, and variable length arrays are a feature of C99.

See this; it's not possible even with MSVC++.

edited May 23 '17 at 11:59

Community

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answered Apr 16 '16 at 10:44

RastaJedi

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score 0 · Answer 2 · answered Apr 16 '16 at 10:58

0

The MSVC on windows does not support VLAs yet, so you will need to make the array with dynamic memory allocation:

static int len = 10;
int main() {
    int *a = malloc(len * sizeof(int));
    if (a == NULL) exit(1);
    return 0;
}

answered Apr 16 '16 at 10:58

fluter

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Array with variable size in C in VS

2 Answers2