For the source code below, compiling gcc -O2/-O3 seem to produce
incorrect code.

-----------------------------------
#include <stdio.h>
int main(int argc, char* argv[])
{
    unsigned int x = 0x12345678;
    unsigned short tmp;
    printf("%x\n", x);
    tmp = ((unsigned short *)&x)[0];
    ((unsigned short *)&x)[0] = ((unsigned short *)&x)[1];
    ((unsigned short *)&x)[1] = tmp;
    printf("%x\n", x);
    return 0;
}
-----------------------------------


% gcc -O1 a.c
% ./a.out 
12345678
56781234

% gcc -O2 a.c
% ./a.out
12345678
12341234

% gcc -v
Using built-in specs.
Configured with: FreeBSD/i386 system compiler
Thread model: posix
gcc version 3.2.1 [FreeBSD] 20021009 (prerelease)




Is this a gcc bug or the source code problem ?

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