C variable declaration place

Question

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Variable declaration placement in C

I really dont understand why when I declare variable 'm' like in snipped code below why it doesn't work???I declare m before I use it so what's the point?? thanks

    int main(){

    int a[] = {2,-4,6,47,59,-6,0};
    sort(a, 7);

    int m;
    for(m = 0; m < 7; m++){
        printf("%d ",a[m]);
    }
}

But if I put declaration at beggining, above the array, it works.

What options did you compile with? – squiguy Oct 27 '12 at 19:55 — squiguy, Oct 27 '12 at 19:55

score 5 · Accepted Answer · answered Oct 27 '12 at 19:58

5

Looks like you are compiling in ANSI C mode. In C89, variable declaration is allowed only at the beginning of a block.

Since C99, this restriction has been removed. Compile with -std=c99 which will allow you to declare variables anywhere.

answered Oct 27 '12 at 19:58

P.P

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I use compiler within Visual Studio 2010, I begin C++ project and in properties change to Compile as C code (/TC) What does it mean?? – exeq Oct 27 '12 at 20:12
Visual Studio supports only few C99 features. So you may have to declare variables at the beginning of a block. Simply move `int m;` to the top of main().For more information: [Visual Studio support for new C / C++ standards?](http://stackoverflow.com/questions/146381/visual-studio-support-for-new-c-c-standards). – P.P Oct 27 '12 at 20:16

score 2 · Answer 2 · answered Oct 27 '12 at 19:54

2

as far as i know in C, all declarations must be above the code

answered Oct 27 '12 at 19:54

Abdusalam Ben Haj

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That used to be the case in C89, it is not so since C99. – Daniel Fischer Oct 27 '12 at 19:57
I studied C as an introductory Course back in 2001, I blame my instructor for not telling me this info lol – Abdusalam Ben Haj Oct 27 '12 at 20:08
Probably he didn't know that then, it was only two years. – Daniel Fischer Oct 27 '12 at 20:09

score 1 · Answer 3 · answered Oct 27 '12 at 19:57

You're probably using a compiler that supports C99 partially(or doesn't support it at all), in which, in-place variable declaration is forbidden.

Using such a compiler would need you to declare your variables before an "executable" code.

This was a restriction in C89 and previous.

score 0 · Answer 4 · answered Oct 27 '12 at 20:13

Not actually an answer but I can't comment on questions yet. I agree with people's answer above regarding the C implementation you;re using is causing the error. What I suggest you try is for (int m = 0, ...) for two reasons: to see if it compiles, and scope (from the looks of it you don't need m outside the for loop) Hope this helps

C variable declaration place

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