daveh@marob.uucp (Dave Hammond) (04/10/91)
[ this is a repost (I'm not sure if the distribution was correct on
the first article) -- apologies if this is a duplicate article ]
In the following code examples, the '\nnn' representation causes the
compiler to sign-extend 8 bit values, causing comparisons to fail (255
!= -1). This occurred on every machine I tested (Generic 386, Altos
386, DEC uVax). Is this because the '\nnn' token being seen as a char
value and chars are signed on the machines I tested on? Or must I
expect this result from all C compilers?
/* c1.c */
main()
{
int a = '\xFF';
printf("a=%o\n",a);
}
/* c2.c */
main()
{
int a = 0xFF;
printf("a=%o\n",a);
}
output from diff c1.s c2.s:
4c4
< TITLE $c1
---
> TITLE $c2
33c33
< mov DWORD PTR [ebp-4], -1
---
> mov DWORD PTR [ebp-4], 255
--
Dave Hammond
daveh@marob.uucp
uunet!rutgers!phri!marob!daveh