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.
