Can the severity of signed/unsigned comparisons be raised, since GCC
does not properly handle the comparisons.
Every example below is false compiled with gcc 4.5.0
int main()
{
int s = -2;
unsigned int u = 0xFFFFFFFDU;
if( s < u )
printf( "okay\n" );
else
printf( "incorrect handling\n" ); // gets here
{
int i = -2;
unsigned u = 2;
if (i < u) {
// Does GCC get here? no, it doesn't
printf( "Ya, of course\n" );
}
else
printf( "gcc puked\n" ); // gets here
}
{
unsigned int i = -3;
if( i < 0 )
printf( "this can't happen, it's unsigned.\n" );
else
printf( "this is actually a correct result here\n" ); // does
get this
}
{
int i = -3;
// visual studio does not warn on this one either... just the first
two comparisons
if( i < (unsigned)0 )
printf( "-3 is < 0 \n" );
else
printf( "-3 is more than 0?\n" ); // gets here
}
return 0;
}
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I said a lot of words on
http://social.msdn.microsoft.com/Forums/en-US/vclanguage/thread/d0ec33f0-2534-48f8-9673-538d68d8ef86
to describe how this might be handled.... and even if 5% of the cases
were fixed, it would be 250% better overall.
I don't know why standards left this open, other than there isn't a
single-instruction translation from code to CPU for the comparison;
But if it's not fixed, this warning should definatly be issued at
default warning level. This should be more like 'if this comparison
can be wrong, it will be wrong'.
