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Asked: 2026-05-10T22:35:19+00:00

I long thought that in C, all variables had to be declared at the

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I long thought that in C, all variables had to be declared at the beginning of the function. I know that in C99, the rules are the same as in C++, but what are the variable declaration placement rules for C89/ANSI C?

The following code compiles successfully with gcc -std=c89 and gcc -ansi:

#include <stdio.h> int main() {     int i;     for (i = 0; i < 10; i++) {         char c = (i % 95) + 32;         printf('%i: %c\n', i, c);         char *s;         s = 'some string';         puts(s);     }     return 0; }

Shouldn’t the declarations of c and s cause an error in C89/ANSI mode?

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1 Answer

  1. It compiles successfully because GCC allows the declaration of s as a GNU extension, even though it’s not part of the C89 or ANSI standard. If you want to adhere strictly to those standards, you must pass the -pedantic flag.

    The declaration of c at the start of a { } block is part of the C89 standard; the block doesn’t have to be a function.

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