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* [Bug tree-optimization/66946] New: Spurious uninitialized warning @ 2015-07-20 16:25 wdijkstr at arm dot com 2015-07-21 13:10 ` [Bug tree-optimization/66946] " wdijkstr at arm dot com ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: wdijkstr at arm dot com @ 2015-07-20 16:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946 Bug ID: 66946 Summary: Spurious uninitialized warning Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: wdijkstr at arm dot com Target Milestone: --- Created attachment 36016 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36016&action=edit preprocessed iso-2022-cn-ext.c Since recently (around May) GCC6 has started to emit spurious uninitialized warnings. An example from building GLIBC (compiled attached pp file with -O2 -Wall -c out.i): In file included from iso-2022-cn-ext.c:659:0: ../iconv/skeleton.c: In function 'gconv': ../iconv/loop.c:325:295: warning: '*((void *)&buf+1)' is used uninitialized in this function [-Wuninitialized] ../iconv/loop.c:325:295: warning: 'buf' is used uninitialized in this function [-Wuninitialized] ../iconv/loop.c:325:295: warning: '*((void *)&buf+1)' is used uninitialized in this function [-Wuninitialized] ../iconv/loop.c:325:295: warning: 'buf' is used uninitialized in this function [-Wuninitialized] In file included from iso-2022-cn-ext.c:659:0: ../iconv/loop.c:435:295: warning: '*((void *)&buf+1)' is used uninitialized in this function [-Wuninitialized] ../iconv/loop.c:435:295: warning: 'buf' is used uninitialized in this function [-Wuninitialized] I checked the control flow and it seems correct. glibc/iconvdata/iso-2022-cn-ext.c calls one of ucs4_to_gb2312, ucs4_to_isoir165 and ucs4_to_cns11643l1 at lines 432-447 - buf is not written if __UNKNOWN_10646_CHAR is returned. In that case however the if statement is executed which does eventually set buf[0] and buf[1]. There is no warning if inlining is disabled, so it is caused by the ucs4_* inline functions not always setting buf. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/66946] Spurious uninitialized warning 2015-07-20 16:25 [Bug tree-optimization/66946] New: Spurious uninitialized warning wdijkstr at arm dot com @ 2015-07-21 13:10 ` wdijkstr at arm dot com 2015-07-21 13:28 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: wdijkstr at arm dot com @ 2015-07-21 13:10 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946 --- Comment #1 from Wilco <wdijkstr at arm dot com> --- Created attachment 36021 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36021&action=edit minimal example Minimal example which still reports the spurious warning. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/66946] Spurious uninitialized warning 2015-07-20 16:25 [Bug tree-optimization/66946] New: Spurious uninitialized warning wdijkstr at arm dot com 2015-07-21 13:10 ` [Bug tree-optimization/66946] " wdijkstr at arm dot com @ 2015-07-21 13:28 ` pinskia at gcc dot gnu.org 2015-07-21 13:31 ` pinskia at gcc dot gnu.org 2015-07-21 13:42 ` wdijkstr at arm dot com 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2015-07-21 13:28 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Comment on attachment 36021 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36021 minimal example written == ((wchar_t) 0xfffd) Will ever be true or is there some sign extending going on which causes this to be false for the default case? ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/66946] Spurious uninitialized warning 2015-07-20 16:25 [Bug tree-optimization/66946] New: Spurious uninitialized warning wdijkstr at arm dot com 2015-07-21 13:10 ` [Bug tree-optimization/66946] " wdijkstr at arm dot com 2015-07-21 13:28 ` pinskia at gcc dot gnu.org @ 2015-07-21 13:31 ` pinskia at gcc dot gnu.org 2015-07-21 13:42 ` wdijkstr at arm dot com 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2015-07-21 13:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946 --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Ok. This just looks like a missing jump threading. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/66946] Spurious uninitialized warning 2015-07-20 16:25 [Bug tree-optimization/66946] New: Spurious uninitialized warning wdijkstr at arm dot com ` (2 preceding siblings ...) 2015-07-21 13:31 ` pinskia at gcc dot gnu.org @ 2015-07-21 13:42 ` wdijkstr at arm dot com 3 siblings, 0 replies; 5+ messages in thread From: wdijkstr at arm dot com @ 2015-07-21 13:42 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946 --- Comment #4 from Wilco <wdijkstr at arm dot com> --- (In reply to Andrew Pinski from comment #2) > Comment on attachment 36021 [details] > minimal example > > written == ((wchar_t) 0xfffd) > > Will ever be true or is there some sign extending going on which causes this > to be false for the default case? The issue seems related to signextension indeed. My GCC builds include this patch: https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00005.html When I disable this new phase the warning disappears, so it might be due to a transformation it makes. The generated code is virtually identical, just different register allocation. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-07-21 13:42 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-07-20 16:25 [Bug tree-optimization/66946] New: Spurious uninitialized warning wdijkstr at arm dot com 2015-07-21 13:10 ` [Bug tree-optimization/66946] " wdijkstr at arm dot com 2015-07-21 13:28 ` pinskia at gcc dot gnu.org 2015-07-21 13:31 ` pinskia at gcc dot gnu.org 2015-07-21 13:42 ` wdijkstr at arm dot com
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