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* [Bug c++/96057] New: -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition
@ 2020-07-04 8:21 haoxintu at gmail dot com
2020-07-04 8:24 ` [Bug c++/96057] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: haoxintu at gmail dot com @ 2020-07-04 8:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96057
Bug ID: 96057
Summary: -Wreturn-type warning message disappears with -O1 to
-Os in unnamed namespace definition
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: haoxintu at gmail dot com
Target Milestone: ---
Hi, all.
This small code, bug.cc, the -Wreturn-type warning disappears when add -O1 or
higher optimization option.
$cat bug.cc
namespace {
int foo() { 1 ? 0 : throw 0 ; }
}
$g++ -c -Wreturn-type -O0 bug.cc
bug.cc: In function 'int {anonymous}::foo()':
bug.cc:2:35: warning: control reaches end of non-void function [-Wreturn-type]
2 | int foo() { 1 ? 0 : throw 0 ; }
|
$g++ -c -Wreturn-type -O1 bug.cc
//emit nothing with -O1 to -Os option
While in Clang, the output of -O0 to -Os is the same. For example,
$clang++ -c -Wreturn-type -O1 bug.cc
bug.cc:2:35: warning: non-void function does not return a value [-Wreturn-type]
int foo() { 1 ? 0 : throw 0 ; }
^
1 warning generated.
$g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/home/haoxin/corpus-compilers/gcc-trunk/gcc-master/build/libexec/gcc/x86_64-pc-linux-gnu/11.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure
--prefix=/home/haoxin/corpus-compilers/gcc-trunk/gcc-master/build/
--enable-languages=c,c++ CC=gcc CXX=g++
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.0.0 20200630 (experimental) (GCC)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/96057] -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition
2020-07-04 8:21 [Bug c++/96057] New: -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition haoxintu at gmail dot com
@ 2020-07-04 8:24 ` pinskia at gcc dot gnu.org
2022-01-05 20:55 ` [Bug c++/96057] [9/10/11/12 Regression] -Wreturn-type warning message disappears with -O1+ in anonymous " pinskia at gcc dot gnu.org
2022-01-21 13:30 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-07-04 8:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96057
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There was another report about static inline where this happens too. The same
reasoning applies here. The function is unused and there for there is no
undefined runtime behavior can happen.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/96057] [9/10/11/12 Regression] -Wreturn-type warning message disappears with -O1+ in anonymous namespace definition
2020-07-04 8:21 [Bug c++/96057] New: -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition haoxintu at gmail dot com
2020-07-04 8:24 ` [Bug c++/96057] " pinskia at gcc dot gnu.org
@ 2022-01-05 20:55 ` pinskia at gcc dot gnu.org
2022-01-21 13:30 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-01-05 20:55 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96057
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|-Wreturn-type warning |[9/10/11/12 Regression]
|message disappears with -O1 |-Wreturn-type warning
|to -Os in unnamed namespace |message disappears with
|definition |-O1+ in anonymous namespace
| |definition
Known to fail| |12.0, 4.4.7
Ever confirmed|0 |1
Target Milestone|--- |9.5
Status|UNCONFIRMED |NEW
Last reconfirmed| |2022-01-05
Known to work| |4.1.2
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/96057] [9/10/11/12 Regression] -Wreturn-type warning message disappears with -O1+ in anonymous namespace definition
2020-07-04 8:21 [Bug c++/96057] New: -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition haoxintu at gmail dot com
2020-07-04 8:24 ` [Bug c++/96057] " pinskia at gcc dot gnu.org
2022-01-05 20:55 ` [Bug c++/96057] [9/10/11/12 Regression] -Wreturn-type warning message disappears with -O1+ in anonymous " pinskia at gcc dot gnu.org
@ 2022-01-21 13:30 ` rguenth at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-01-21 13:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96057
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |WONTFIX
Status|NEW |RESOLVED
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
That's because the -Wreturn-type diagnostic happens after we remove unused
functions which we only do at -O1+:
t.c: At global scope:
t.c:2:9: warning: 'int {anonymous}::foo()' defined but not used
[-Wunused-function]
2 | int foo() { 1 ? 0 : throw 0 ; }
| ^~~
which in turn is because the function is local (in an anonymous namespace).
Likely GCC 4.1 removed the function only later.
IMHO a WONTFIX, sorry.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-01-21 13:30 UTC | newest]
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-- links below jump to the message on this page --
2020-07-04 8:21 [Bug c++/96057] New: -Wreturn-type warning message disappears with -O1 to -Os in unnamed namespace definition haoxintu at gmail dot com
2020-07-04 8:24 ` [Bug c++/96057] " pinskia at gcc dot gnu.org
2022-01-05 20:55 ` [Bug c++/96057] [9/10/11/12 Regression] -Wreturn-type warning message disappears with -O1+ in anonymous " pinskia at gcc dot gnu.org
2022-01-21 13:30 ` rguenth at gcc dot gnu.org
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