https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106008
Bug ID: 106008
Summary: [12 Regression] warning: ‘(((char *)loadcmds.113_68 +
_933 + 16))[329406144173384849].mapend’ may be used
uninitialized [-Wmaybe-uninitialized]
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
Target Milestone: ---
Created attachment 53156
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53156&action=edit
A testcase
When building glibc master branch with -mavx512f, I got
[hjl@gnu-tgl-2 tmp]$ gcc -O2 -march=x86-64 -S -Wall x.i -mavx512f
dl-load.c: In function ‘_dl_map_object_from_fd.constprop’:
dl-load.c:1158:30: warning: ‘(((char *)loadcmds.113_68 + _933 +
16))[329406144173384849].mapend’ may be used uninitialized
[-Wmaybe-uninitialized]
[hjl@gnu-tgl-2 tmp]$
The code looks like
struct loadcmd *c = &loadcmds[nloadcmds++];
c->mapstart = ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize));
c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize));
c->dataend = ph->p_vaddr + ph->p_filesz;
c->allocend = ph->p_vaddr + ph->p_memsz;
/* Remember the maximum p_align. */
if (powerof2 (ph->p_align) && ph->p_align > p_align_max)
p_align_max = ph->p_align;
c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize));
/* Determine whether there is a gap between the last segment
and this one. */
if (nloadcmds > 1 && c[-1].mapend != c->mapstart)
has_holes = true;
c[-1].mapend should always be initialized.
