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* [Bug c/11663] New: gcc ignores the cast and emits a warning
@ 2003-07-24 17:34 jashepherd at usa dot net
2003-07-24 18:14 ` [Bug c/11663] " pinskia at physics dot uc dot edu
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: jashepherd at usa dot net @ 2003-07-24 17:34 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11663
Summary: gcc ignores the cast and emits a warning
Product: gcc
Version: 2.96 (redhat)
Status: UNCONFIRMED
Severity: minor
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jashepherd at usa dot net
CC: gcc-bugs at gcc dot gnu dot org
gcc -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.2 2.96-116.7.2)
/*
gcc ignores the cast and emits a warning
gcc bug.c -funsigned-char
bug.c: In function `main':
bug.c:13: warning: comparison is always true due to limited range of data type
*/
char trans_ind = 3;
int main(int argc, char *argv[])
{
if ((short)trans_ind >= 0 && (short)trans_ind <= 3)
printf("Yes\n");
else
printf("No\n");
return(0);
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/11663] gcc ignores the cast and emits a warning
2003-07-24 17:34 [Bug c/11663] New: gcc ignores the cast and emits a warning jashepherd at usa dot net
@ 2003-07-24 18:14 ` pinskia at physics dot uc dot edu
2003-07-24 18:54 ` jashepherd at usa dot net
2003-07-24 19:02 ` pinskia at physics dot uc dot edu
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at physics dot uc dot edu @ 2003-07-24 18:14 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11663
pinskia at physics dot uc dot edu changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Keywords| |diagnostic
Resolution| |INVALID
Summary|gcc ignores the cast and |gcc ignores the cast and
|emits a warning |emits a warning
Target Milestone|3.4 |---
------- Additional Comments From pinskia at physics dot uc dot edu 2003-07-24 18:14 -------
The warning is correct because converting unsigned char to short will always be positive
or zero. GCC is keeping the range information for trans_ind, if you want to convert
unsigned char to signed short with trans_ind > 127 being negative add a cast to signed
char first.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/11663] gcc ignores the cast and emits a warning
2003-07-24 17:34 [Bug c/11663] New: gcc ignores the cast and emits a warning jashepherd at usa dot net
2003-07-24 18:14 ` [Bug c/11663] " pinskia at physics dot uc dot edu
@ 2003-07-24 18:54 ` jashepherd at usa dot net
2003-07-24 19:02 ` pinskia at physics dot uc dot edu
2 siblings, 0 replies; 4+ messages in thread
From: jashepherd at usa dot net @ 2003-07-24 18:54 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11663
------- Additional Comments From jashepherd at usa dot net 2003-07-24 18:54 -------
Subject: Re: gcc ignores the cast and emits a warning
A cast to (short) has to assume the constraints of the cast datatype
not the original data type.
The result of the entire if test
if ((short)trans_ind >= 0 && (short)trans_ind <= 3)
can never be 'always true' regardless of whether the datatype
is char, unsigned char or short.
only in the case where the test is
if ( trans_ind >= 0 )
would the warning be valid.
At 2003-07-24 18:14 +0000, you wrote:
>PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
>
>http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11663
>
>
>pinskia at physics dot uc dot edu changed:
>
> What |Removed |Added
>----------------------------------------------------------------------------
> Status|UNCONFIRMED |RESOLVED
> Keywords| |diagnostic
> Resolution| |INVALID
> Summary|gcc ignores the cast and |gcc ignores the cast and
> |emits a warning |emits a warning
> Target Milestone|3.4 |---
>
>
>------- Additional Comments From pinskia at physics dot uc dot
>edu 2003-07-24 18:14 -------
>The warning is correct because converting unsigned char to short will
>always be positive
>or zero. GCC is keeping the range information for trans_ind, if you want
>to convert
>unsigned char to signed short with trans_ind > 127 being negative add a
>cast to signed
>char first.
>
>
>
>------- You are receiving this mail because: -------
>You reported the bug, or are watching the reporter.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/11663] gcc ignores the cast and emits a warning
2003-07-24 17:34 [Bug c/11663] New: gcc ignores the cast and emits a warning jashepherd at usa dot net
2003-07-24 18:14 ` [Bug c/11663] " pinskia at physics dot uc dot edu
2003-07-24 18:54 ` jashepherd at usa dot net
@ 2003-07-24 19:02 ` pinskia at physics dot uc dot edu
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at physics dot uc dot edu @ 2003-07-24 19:02 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11663
------- Additional Comments From pinskia at physics dot uc dot edu 2003-07-24 19:02 -------
But keeping the range information (because the cast will not change the sign in this case) is still
valid so the warning still stands.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2003-07-24 19:02 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2003-07-24 17:34 [Bug c/11663] New: gcc ignores the cast and emits a warning jashepherd at usa dot net
2003-07-24 18:14 ` [Bug c/11663] " pinskia at physics dot uc dot edu
2003-07-24 18:54 ` jashepherd at usa dot net
2003-07-24 19:02 ` pinskia at physics dot uc dot edu
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