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List:       asterisk-dev
Subject:    [asterisk-dev] gcc bug with zero-sized arrays and struct
From:       Luigi Rizzo <rizzo () icir ! org>
Date:       2007-10-30 10:27:41
Message-ID: 20071030032741.A86261 () xorpc ! icir ! org
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Some time ago i hit a problem with chan_iax which I eventually tracked
down as related to the problem below - namely a compiler bug with
struct initializers after zero-sized arrays.

This was with gcc 2.95 - now, i know this is obsolete, but the bug is
very subtle and it is unclear that other compiler versions are not
affected.

I am mentioning it in this list because this construct is used widely
in asterisk (string fields have a zero-sized array used as a marker),
and it would be good to check whether other compiler versions handle
this correctly.

	cheers
	luigi


/* This code shows a problem with gcc 2.95, 0-sized arrays and initializers:
 * Initializing a field right after a 0-sized array fails (the compiler emits
 * no code).
 */

struct foo {
        char *pre[0];
        int a;
};

struct bar {
        char *pre[1];
        int a;
};

int main(int argc, char *argv[])
{
        struct foo a = { .a = 123 };
        struct bar b = { .a = 123 };

        printf("a.a is %d, should be 123\n", a.a);
        printf("b.a is %d, should be 123\n", b.a);
        return 0;
}


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