sbrk return (was: att & osf)

[Doug Gwyn]

In article <3498 at encore.UUCP> bzs at encore.UUCP (Barry Shein) writes:
>Consider that sbrk() returns -1 (specifically, (char *)-1) as an error
>code in all Unix's I know of (BSD, SYSV.)

Actually it's not clear WHAT sbrk() returns for an error indication,
when expressed in C.  Traditionally (because of usage of a common
error handling return by all system call interfaces) it returns an
int with value -1, which may not even be in the same register as a
char * is returned in.  This is a horrible botch that COULD have been
fixed over the years by a phased transition strategy:
	0) existing bogus -1 return from sbrk
	1) edit applications to accept bogus -1 or useful 0 for error
	2) change sbrk to return 0 on error
	3) (optional) edit applications to no longer check bogus -1.
Other similar problems have been fixed by such a strategy.

The analogous IPC botch is less excusable, as the final form of that
interface was frozen several years after the problem with -1 as a
char * was well known.

P.S.  To avoid the problem with sbrk(), change
	if ( sbrk( incr ) == ??? )
		error();
to
	curbrk = sbrk( 0 );
	if ( brk( curbrk + incr ) == 0 )
		error();