Array subscript in C

Question

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,

This is not a duplicate, the OP doesn't care how they are implemented. — Iharob Al Asimi, Mar 05 '15 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. — Ben Voigt, Mar 05 '15 at 18:55

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

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]; };
    }

edited Jun 20 '20 at 09:12

Community

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answered Mar 05 '15 at 18:43

Greg Hewgill

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I don't think this is the question. – Iharob Al Asimi Mar 05 '15 at 18:44
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@iharob: As requested in the question, this is the "relevant GCC document that specifies it's okay to declare". – Greg Hewgill Mar 05 '15 at 18:45

score 0 · Answer 2 · answered Mar 05 '15 at 18:44

0

As stated here

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

answered Mar 05 '15 at 18:44

Eugene Sh.

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Array subscript in C

2 Answers2