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I have been looking for related GCC document which allows to declare something like this. 

unsigned int subs = 10;
unsigned int array1[subs];

I'm aware such declaration is valid and work using gcc. I would like to get the relevant GCC document that specifies it's okay to declare.

Thanks,

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  • gcc.gnu.org/onlinedocs/gcc/Variable-Length.html ? Commented Mar 5, 2015 at 18:42
  • 3
    Is also valid in C99 Commented Mar 5, 2015 at 18:43
  • This is not a duplicate, the OP doesn't care how they are implemented. Commented Mar 5, 2015 at 18:53
  • @iharob: Duplicate means that the other question is a superset and also provides the answer to this. Which it does. The accepted answer has a link to the documentation and additionally shows what the compiler produces. The fact that this question doesn't ask for the second part doesn't make it deserve a duplicated answer. Commented Mar 5, 2015 at 18:55

2 Answers 2

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From 6.9 Arrays of Variable Length:

As an extension, GCC accepts variable-length arrays as a member of a structure or a union. For example:

    void
    foo (int n)
    {
      struct S { int x[n]; };
    }
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2 Comments

I don't think this is the question.
@iharob: As requested in the question, this is the "relevant GCC document that specifies it's okay to declare".
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As stated here

Another GNU extension allows you to declare an array size using variables, rather than only constants.

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