https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88889
Bug ID: 88889
Summary: [9 Regression] New valgrind warning since r261039
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: marxin at gcc dot gnu.org
Target Milestone: ---
I've just isolated a test-case from curl package and there's a new valgrind
error:
$ cat lib1560.c
void
__attribute__((noipa))
updateurl(const char *p)
{
char part[16];
if(1 == __builtin_sscanf(p, "%1[^=]=", part)) {
{
__builtin_printf ("part:%s\n", part);
int what = __builtin_strcmp("1234567", part);
if(!what)
__builtin_abort ();
}
}
}
int main()
{
updateurl("a=");
return 0;
}
$ gcc lib1560.c -O2 -g && valgrind ./a.out
==4115== Memcheck, a memory error detector
==4115== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==4115== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==4115== Command: ./a.out
==4115==
part:a
==4115== Conditional jump or move depends on uninitialised value(s)
==4115== at 0x40119D: updateurl (lib1560.c:9)
==4115== by 0x40106D: main (lib1560.c:18)
we correctly emit:
what_7 = __builtin_strcmp_eq ("1234567", &part, 8);
which is transformed into following assembly:
movabsq $15540725856023089, %rax
cmpq %rax, (%rsp)
That's correct transformation, but as part[2:] is uninitialized, valgrind
complains about comparison of the uninitialized bytes of 'part'.
What to do with that?
