https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80147
Bug ID: 80147
Summary: missing maybe-uninitialized warning on variable with
no side effects
Product: gcc
Version: 6.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vincent-gcc at vinc17 dot net
Target Milestone: ---
On the following test, GCC 6.3.0 with -Wuninitialize and -Wmaybe-uninitialized
(both implied by -Wall) warns as expected in the 4 cases without optimization,
but if -O is used, GCC misses the warning for j1.
----------------------------------------
void f0 (int i);
static void f1 (int i) { }
static void f2 (int i) { f0 (i); }
void g (int b)
{
int i1, i2, j1, j2;
f1 (i1);
f2 (i2);
if (b)
{
f1 (j1);
f2 (j2);
}
}
----------------------------------------
The following is OK:
zira% gcc -Wall -c tst.c
tst.c: In function ‘g’:
tst.c:8:3: warning: ‘i1’ is used uninitialized in this function
[-Wuninitialize]
f1 (i1);
^~~~~~~
tst.c:9:3: warning: ‘i2’ is used uninitialized in this function
[-Wuninitialize]
f2 (i2);
^~~~~~~
tst.c:12:7: warning: ‘j1’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
f1 (j1);
^~~~~~~
tst.c:13:7: warning: ‘j2’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
f2 (j2);
^~~~~~~
But the warning for j1 is missing if -O is added:
zira% gcc -Wall -c tst.c -O
tst.c: In function ‘g’:
tst.c:8:3: warning: ‘i1’ is used uninitialized in this function
[-Wuninitialize]
f1 (i1);
^~~~~~~
tst.c:9:3: warning: ‘i2’ is used uninitialized in this function
[-Wuninitialize]
f2 (i2);
^~~~~~~
tst.c:3:26: warning: ‘j2’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
static void f2 (int i) { f0 (i); }
^~~~~~
tst.c:7:19: note: ‘j2’ was declared here
int i1, i2, j1, j2;
^~
