Another strict-alias puzzle with (unsigned) char ptrs

Adam Dickmeiss adam@indexdata.dk
Tue Sep 26 21:02:00 GMT 2006


The program below prints 1 or 0 depending on GCC version and 
-O2/-fstrict-aliasing being present or not. With proper optimizations 
enabled, 0 is printed. Otherwise, 1 is printed.

So just to understand: strict aliases also take effect for 
signed/unsigned char pointers?
/ Adam


#include <stdio.h>

static void decode_ptr(const unsigned char **src)
{
     (*src)++;
}

int main(int argc, char **argv)
{
     const char *src0 = "";
     const char *src = src0;

     decode_ptr(&src);
     printf("sz = %lld\n", (long long)(src - src0));
}



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