chars in conditional expression, 3b2 C compiler

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6 total messages Started by Dean Long Thu, 25 Dec 1986 23:23

#462

Author: Dean Long
Date: Thu, 25 Dec 1986 23:23

23 lines
1079 bytes

Try these two commands on a 3b2 running SYSV unix on the following program:

cc -c sub.c		# should work OK
cc -DCRASH -c sub.c	# /lib/ccom should core dump

Does anyone have any ideas?
----------------------------------------------------------------------

sub()
{
        char x;
        int i;

        i = ((x > 0) ? 1 : 0);
        i = ((x >= 1) ? 1 : 0);
#ifdef CRASH
        i = ((x >= 0) ? 1 : 0);
#endif
}
-- 
Dean Long
San Diego State Univ.
sdcsvax!sdsu!dlong

Re: chars in conditional expression, 3b2 C compiler

#463

Author: Kim Chr. Madsen
Date: Tue, 30 Dec 1986 23:00

22 lines
1176 bytes

In article <2489@sdsu.UUCP>, dlong@sdsu.UUCP (Dean Long) writes:
> Try these two commands on a 3b2 running SYSV unix on the following program:
> 
> cc -c sub.c		# should work OK
> cc -DCRASH -c sub.c	# /lib/ccom should core dump
> 
> [some code]....

Well, tried this one out without any problems on this 3b2 running UNIX
System V R2.1 are you running Release 3 or an older (pre 2.1 release)
system V.

The only thing that really bugs me is the fact that chars are unsigned
and therefore the following code will fail:

	while ((c=getc(stream)) != EOF) putchar(c);

And you will have to redefine EOF to 255 (0377 or 0xff) or cast it to a char!

						Kim Chr. Madsen

Re: chars in conditional expression, 3b2 C compiler (Now stdio)

#448

Author: Jim Webb
Date: Fri, 02 Jan 1987 01:07

12 lines
1050 bytes

> The only thing that really bugs me is the fact that chars are unsigned
> and therefore the following code will fail:
> 
> 	while ((c=getc(stream)) != EOF) putchar(c);
> 
> And you will have to redefine EOF to 255 (0377 or 0xff) or cast it to a char!

Ummm.  I always declare c as an int, not a char, and everything works fine
and dandy...
-- 
Jim Webb             "Out of phase--get help"          ...!ihnp4!hropus!jrw
    "Make sure comments and code agree.  If not, write a man page..."

Re: chars in conditional expression, 3b2 C compiler

#449

Author: James Van Artsdalen
Date: Fri, 02 Jan 1987 11:19

18 lines
1542 bytes

IN article <189@olamb.UUCP>, kimcm@olamb.UUCP (Kim Chr. Madsen) wrote:
> The only thing that really bugs me is the fact that chars are unsigned
> and therefore the following code will fail:
> 
> 	while ((c=getc(stream)) != EOF) putchar(c);
> 
> And you will have to redefine EOF to 255 (0377 or 0xff) or cast it to a char!

This code will fail no matter how chars are handled, assuming "c" is a "char".
If you remember that getc() returns an *int*, not a char, and have "int c"
instead of "char c", this works just fine.

If "c" is declared "char c;", the while loop above is broken even with signed
chars: what happens to the while loop if a 0xff is in the file?  It terminates
early, whereas if c is "int c;" is works OK.  lint will find this kind of bug.
-- 
James R. Van Artsdalen   ...!ut-sally!utastro!bigtex!james   "Live Free or Die"
Voice: (512)-323-2675  Modem: (512)-323-2773  5300B McCandless, Austin TX 78756

Re: chars in conditional expression, 3b2 C compiler

#450

Author: Mike Stump
Date: Sat, 03 Jan 1987 23:44

14 lines
1247 bytes

In article <189@olamb.UUCP> kimcm@olamb.UUCP (Kim Chr. Madsen) writes:
>In article <2489@sdsu.UUCP>, dlong@sdsu.UUCP (Dean Long) writes:
>> Try these two commands on a 3b2 running SYSV unix on the following program:
>> [edited for space]
>Well, tried this one out without any problems on this 3b2 running UNIX
>System V R2.1 are you running Release 3 or an older (pre 2.1 release)
>system V.

I tried it on 3b5 System V Version 2 release 2.0 and it bombs.
Looks like they fix the problem in 2.1...
Dean is probably running 2.0, like me.
I will be happy when we upgrade to a 3b15, and S5V3...

					Mike Stump

Re: chars in conditional expression, 3b2 C compiler

#451

Author: Doug Gwyn
Date: Mon, 05 Jan 1987 18:00

11 lines
1144 bytes

In article <189@olamb.UUCP> kimcm@olamb.UUCP (Kim Chr. Madsen) writes:
-The only thing that really bugs me is the fact that chars are unsigned
-and therefore the following code will fail:
-	while ((c=getc(stream)) != EOF) putchar(c);
-And you will have to redefine EOF to 255 (0377 or 0xff) or cast it to a char!

I suspect there will be a zillion follow-ups explaining
that getc() returns an (int), not a (char), and that EOF
should remain defined as -1.  This has been hashed over
many times in net.lang.c.  It is not a bug in the 3B2 C
implementation.

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