Variable-Length Arrays in c programming

Question

I want to create an variable-length array. Here is my code:

#include <stdio.h>

int main (void)
{
    int n,i, response;
    while(true){
        printf("Enter the number of responses:");
        scanf("%i",&n);
        if(n<1){
            printf("Wrong number\n");
        }
        else
            break;
    } 
    int raiting[n];
}

Here I assign the value, that user enter, to the variable n and the value should be greater than one.

But it give me errors:

1)expected constant expression

2)cannot allocate an array of constant size 0

3)'raiting unknown size'

I am using Visual Studio.

How can I fix that? Why it's wrong?

What compiler are you using, and what compiler flags are you passing it? VLAs require C99 support. — interjay, Sep 12 '16 at 17:00
Normally, when one wants a variable-sized array, they allocate memory for it on the heap with `malloc`. — ForceBru, Sep 12 '16 at 17:02
@interjay I am using Visual Studio. So, the problem is in compiler? Everything is ok with code? — Daniel Yefimov, Sep 12 '16 at 17:05
@ForceBru `malloc()` does not provide an _array_, but a pointer to memory. Although similar, there are differences. See C11 6.7.6.2 2 Array declarators. — chux - Reinstate Monica, Sep 12 '16 at 17:06
@interjay: **at least** C99. C11 also supports them (they have been made optional, though). — too honest for this site, Sep 12 '16 at 17:06
visual studio 2015 incorporates a number of tools and compilers. Are you using a C++ compiler or a C compiler within visual studio 2015? — chux - Reinstate Monica, Sep 12 '16 at 17:07
@chux, this is why I said `malloc` _allocates memory_ for data. — ForceBru, Sep 12 '16 at 17:07
Visual Studio doesn't support a lot of C99. I don't think it has VLAs. — interjay, Sep 12 '16 at 17:07
MSVC is not standard compliant and never has supported C99. Get a modern compiler like gcc or clang which **are** standard compliant. Note this does not only apply to VLAs, but also other modern features of C which are introduced with C99. — too honest for this site, Sep 12 '16 at 17:07
@Olaf Thank you! Which compiler would you advice: gcc or clang? — Daniel Yefimov, Sep 12 '16 at 17:10
I'm fine with gcc, but actually don't use clang, so far. For standard code both should be fine. — too honest for this site, Sep 12 '16 at 17:13
@ForceBru OP clearly wants a variable length array, VLA, which has a specific meaning in C. — hyde, Sep 12 '16 at 17:20
Sidenote: check for `n <= 0` to avoid a zero-length array (valid, but nonsense). — too honest for this site, Sep 12 '16 at 17:22
This question was answered here:http://stackoverflow.com/questions/5246900/enabling-vlasvariable-length-arrays-in-ms-visual-c. The bottom line: MSVC is not C99 compliant and doesn't support VLAs. I tried to suggest an alternative, but for whatever reason you did not like it. — Victor Havin, Sep 15 '16 at 19:19

Variable-Length Arrays in c programming

0 Answers0