[SystemSafety] Fwd: Re: Correcting the SECOND screw-up (grovelling apologies)

[Derek M Jones]

Roberto,

>    sizeof(char) == sizeof(int) == 1

The (common) assumption that this does not occur creates all
manner of interesting behavior, when it does occur.

Other common assumptions tend to involve equalities holding,
such as:

sizeof(int) == sizeof(long)    // once a very common assumption
sizeof(long) == sizeof(void *) // still common


I believe the following does not rely on undefined behavior (because
conversion of negative values is defined for unsigned):

#include <limits.h>
#include <stdio.h>

int main(void)
{
char ch=CHAR_MIN;

if (ch < 0)
    printf("char is signed\n");
else
    printf("char is unsigned\n");

}


-- 
Derek M. Jones           Evidence-based software engineering
tel: +44 (0)1252 520667  blog:shape-of-code.coding-guidelines.com