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* [Bug c++/24770] New: Incorrect "unreachable code" warning from 3.4.3 under specific conditions
@ 2005-11-09 23:51 dgsteffen at numerica dot us
2005-11-10 0:01 ` [Bug middle-end/24770] [3.4 Regression] " pinskia at gcc dot gnu dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: dgsteffen at numerica dot us @ 2005-11-09 23:51 UTC (permalink / raw)
To: gcc-bugs
This may be a duplicate of 8828, I'm not sure. (8828 is marked 'resolved' for
3.2.)
The following short program produces an incorrect warning about unreachable
code; this error is fragile, in that changing just about anything results in
correct behavior (e.g. no warning); details follow. The code is this:
#include <iostream>
#include <cmath>
using namespace std;
inline double DoThing(int dim = 3)
{
switch (dim) {
case 2:
return 2;
case 3:
return 3;
default:
return 4;
}
}
int main()
{
cout << sqrt( DoThing(2) ) << endl;
}
The compile command is this:
/usr/local/compilers/3.4/bin/c++ -Wall -Werror -O2 -o check check.C
and the result is:
check.C: In function `int main()':
check.C:9: warning: unreachable code at beginning of switch statement
Changing the value passed into DoThing (or removing it) does not change the
behavior. Things that _do_ change the behavior (e.g. result in no warnings and
a correct compile) are: compiling without optimization; remove 'inline'; change
return type of DoThing to int; don't take the sqrt of the answer.
Unfortunately I don't have a more recent version to test with. GCC 3.3 and 3.2
do not display this behavior.
Details about our compiler: /usr/local/compilers/3.4/bin/c++ -v
Reading specs from
/usr/local/compilers/.gcc-3.4.3/bin/../lib/gcc/i686-pc-linux-gnu/3.4.3/specs
Configured with: ./configure
--prefix=/scratch/mpdegroat/software/gcc-3.4.3/.gcc-3.4.3 --enable-shared
--enable-threads=posix --enable-__cxa_atexit --disable-checking
--with-system-zlib
Thread model: posix
gcc version 3.4.3
Please don't hesitate to bug me for more information! Thanks very much.
Dave Steffen, Ph.D.
Software Engineer IV
Numerica Corporation
ph (970) 419-8343 x27
fax (970) 223-6797
dgsteffen@numerica.us
--
Summary: Incorrect "unreachable code" warning from 3.4.3 under
specific conditions
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: dgsteffen at numerica dot us
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24770
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/24770] [3.4 Regression] Incorrect "unreachable code" warning from 3.4.3 under specific conditions
2005-11-09 23:51 [Bug c++/24770] New: Incorrect "unreachable code" warning from 3.4.3 under specific conditions dgsteffen at numerica dot us
@ 2005-11-10 0:01 ` pinskia at gcc dot gnu dot org
2005-11-21 2:44 ` gdr at gcc dot gnu dot org
2006-03-01 4:59 ` gdr at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-11-10 0:01 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2005-11-10 00:01 -------
Confirmed, only a 3.4 regression.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Component|c++ |middle-end
Ever Confirmed|0 |1
Keywords| |diagnostic
Known to fail| |3.4.0 3.4.5
Known to work| |4.0.0 4.1.0
Last reconfirmed|0000-00-00 00:00:00 |2005-11-10 00:01:21
date| |
Summary|Incorrect "unreachable code"|[3.4 Regression] Incorrect
|warning from 3.4.3 under |"unreachable code" warning
|specific conditions |from 3.4.3 under specific
| |conditions
Target Milestone|--- |3.4.5
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24770
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/24770] [3.4 Regression] Incorrect "unreachable code" warning from 3.4.3 under specific conditions
2005-11-09 23:51 [Bug c++/24770] New: Incorrect "unreachable code" warning from 3.4.3 under specific conditions dgsteffen at numerica dot us
2005-11-10 0:01 ` [Bug middle-end/24770] [3.4 Regression] " pinskia at gcc dot gnu dot org
@ 2005-11-21 2:44 ` gdr at gcc dot gnu dot org
2006-03-01 4:59 ` gdr at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: gdr at gcc dot gnu dot org @ 2005-11-21 2:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from gdr at gcc dot gnu dot org 2005-11-21 02:44 -------
Not release critical.
Postponed until GCC 3.4.6
--
gdr at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |gdr at gcc dot gnu dot org
Target Milestone|3.4.5 |3.4.6
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24770
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug middle-end/24770] [3.4 Regression] Incorrect "unreachable code" warning from 3.4.3 under specific conditions
2005-11-09 23:51 [Bug c++/24770] New: Incorrect "unreachable code" warning from 3.4.3 under specific conditions dgsteffen at numerica dot us
2005-11-10 0:01 ` [Bug middle-end/24770] [3.4 Regression] " pinskia at gcc dot gnu dot org
2005-11-21 2:44 ` gdr at gcc dot gnu dot org
@ 2006-03-01 4:59 ` gdr at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: gdr at gcc dot gnu dot org @ 2006-03-01 4:59 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from gdr at gcc dot gnu dot org 2006-03-01 04:59 -------
Fixed in 4.0.0. and up
--
gdr at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
Target Milestone|3.4.6 |4.0.0
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24770
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2006-03-01 4:59 UTC | newest]
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2005-11-09 23:51 [Bug c++/24770] New: Incorrect "unreachable code" warning from 3.4.3 under specific conditions dgsteffen at numerica dot us
2005-11-10 0:01 ` [Bug middle-end/24770] [3.4 Regression] " pinskia at gcc dot gnu dot org
2005-11-21 2:44 ` gdr at gcc dot gnu dot org
2006-03-01 4:59 ` gdr at gcc dot gnu dot org
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