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* [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
@ 2012-12-20 15:36 bp at alien8 dot de
2012-12-20 15:43 ` [Bug regression/55759] " rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: bp at alien8 dot de @ 2012-12-20 15:36 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
Bug #: 55759
Summary: bogus warning when building drivers/ata/libata-core.c
in v3.7 of the linux kernel
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: regression
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: bp@alien8.de
Hi,
when building kernel v3.7 with Debian's gcc: (Debian 4.7.2-4) 4.7.2, I
get the following warning:
$ make CC=gcc-4.7 drivers/ata/libata-core.o
make[1]: Nothing to be done for `all'.
make[1]: Nothing to be done for `relocs'.
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CC kernel/bounds.s
GEN include/generated/bounds.h
CC arch/x86/kernel/asm-offsets.s
GEN include/generated/asm-offsets.h
CALL scripts/checksyscalls.sh
CC scripts/mod/empty.o
MKELF scripts/mod/elfconfig.h
HOSTCC scripts/mod/file2alias.o
HOSTCC scripts/mod/modpost.o
HOSTCC scripts/mod/sumversion.o
HOSTLD scripts/mod/modpost
CC drivers/ata/libata-core.o
drivers/ata/libata-core.c: In function ‘ata_hpa_resize’:
drivers/ata/libata-core.c:1397:3: warning: ‘native_sectors’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
$
it falsely complains that native_sectors might be used unitialized. The
variable's value is assigned-to in an auxiliary function and passed to
it as a pointer.
The auxiliary function returns negative value on error and 0 on success
and its caller uses the native_sectors value returned over the pointer
only in the success case and in that case, native_sectors is always
properly initialized.
Also, gcc-4.6 (gcc-4.6 (Debian 4.6.3-14) 4.6.3) doesn't trigger that
same warning:
$ make CC=gcc-4.6 drivers/ata/libata-core.o
make[1]: Nothing to be done for `all'.
make[1]: Nothing to be done for `relocs'.
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CALL scripts/checksyscalls.sh
CC drivers/ata/libata-core.o
$
Thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug regression/55759] bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
@ 2012-12-20 15:43 ` rguenth at gcc dot gnu.org
2012-12-20 16:20 ` bp at alien8 dot de
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2012-12-20 15:43 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2012-12-20
Ever Confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2012-12-20 15:43:24 UTC ---
Please provide preprocessed source.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug regression/55759] bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
2012-12-20 15:43 ` [Bug regression/55759] " rguenth at gcc dot gnu.org
@ 2012-12-20 16:20 ` bp at alien8 dot de
2012-12-20 16:38 ` markus at trippelsdorf dot de
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: bp at alien8 dot de @ 2012-12-20 16:20 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
--- Comment #2 from Boris <bp at alien8 dot de> 2012-12-20 16:20:34 UTC ---
Created attachment 29015
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29015
gzipped preprocessed source of drivers/ata/libata-core.c
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug regression/55759] bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
2012-12-20 15:43 ` [Bug regression/55759] " rguenth at gcc dot gnu.org
2012-12-20 16:20 ` bp at alien8 dot de
@ 2012-12-20 16:38 ` markus at trippelsdorf dot de
2012-12-20 18:34 ` markus at trippelsdorf dot de
2013-11-20 0:42 ` law at redhat dot com
4 siblings, 0 replies; 6+ messages in thread
From: markus at trippelsdorf dot de @ 2012-12-20 16:38 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
Markus Trippelsdorf <markus at trippelsdorf dot de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |markus at trippelsdorf dot
| |de
--- Comment #3 from Markus Trippelsdorf <markus at trippelsdorf dot de> 2012-12-20 16:38:04 UTC ---
It only happens with -Os, -O2 is fine.
gcc-4.8 is also affected.
I'm reducing this testcase right now.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug regression/55759] bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
` (2 preceding siblings ...)
2012-12-20 16:38 ` markus at trippelsdorf dot de
@ 2012-12-20 18:34 ` markus at trippelsdorf dot de
2013-11-20 0:42 ` law at redhat dot com
4 siblings, 0 replies; 6+ messages in thread
From: markus at trippelsdorf dot de @ 2012-12-20 18:34 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
--- Comment #4 from Markus Trippelsdorf <markus at trippelsdorf dot de> 2012-12-20 18:34:19 UTC ---
This is what creduce came up with:
markus@x4 /tmp % cat test.i
struct ata_taskfile
{
int feature;
};
struct ata_eh_info
{
int flags;
};
struct ata_eh_context
{
struct ata_eh_info i;
};
struct
{
struct ata_eh_context eh_context;
}
g, n;
int a, c, e, f, m, o;
void fn1 (char *, ...);
int fn2 ();
int fn3 ();
static int
fn4 (long long *p1)
{
struct ata_taskfile b;
if (a && b.feature)
return 1;
*p1 = fn3 ();
return 0;
}
static int
fn5 ()
{
struct ata_taskfile d;
if (c && d.feature)
return -13;
return 0;
}
static int
fn6 ()
{
struct ata_eh_context h = g.eh_context;
int i = h.i.flags, l;
_Bool j = f;
long long k;
l = fn4 (&k);
if (l)
return 0;
if (e || j)
return 0;
l = fn5 ();
if (l == -13)
return 0;
if (l)
return 1;
l = fn2 ();
if (l)
if (i)
fn1 ("HPA > %llu\n", k);
return 0;
}
int
fn7 ()
{
struct ata_eh_context p = n.eh_context;
int q = p.i.flags;
o = 0;
m = fn6 ();
goto err_out_nosup;
if (q)
err_out_nosup:
return 0;
}
markus@x4 /tmp % gcc -c -Wall -Os test.i
test.i: In function ‘fn7’:
test.i:61:17: warning: ‘k’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
fn1 ("HPA > %llu\n", k);
^
test.i:47:15: note: ‘k’ was declared here
long long k;
^
markus@x4 /tmp % gcc -c -Wall test.i
markus@x4 /tmp % gcc -c -Wall -O2 test.i
markus@x4 /tmp % /usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3/gcc -c -Wall -Os test.i
markus@x4 /tmp % /usr/x86_64-pc-linux-gnu/gcc-bin/4.7.2/gcc -c -Wall -Os test.i
test.i: In function ‘fn7’:
test.i:61:17: warning: ‘k’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
test.i:47:15: note: ‘k’ was declared here
markus@x4 /tmp % /usr/x86_64-pc-linux-gnu/gcc-bin/4.7.2/gcc -c -Wall -O2 test.i
markus@x4 /tmp %
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug regression/55759] bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel
2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
` (3 preceding siblings ...)
2012-12-20 18:34 ` markus at trippelsdorf dot de
@ 2013-11-20 0:42 ` law at redhat dot com
4 siblings, 0 replies; 6+ messages in thread
From: law at redhat dot com @ 2013-11-20 0:42 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55759
Jeffrey A. Law <law at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #5 from Jeffrey A. Law <law at redhat dot com> ---
-Os was changed to throttle jump threading as the block copying can result in
larger code. With jump threading throttled, unexecutable paths are left in the
CFG which reduces the preciseness of warnings such as Wuninitialized.
Tracking via BZ 42145, but not expecting to fix it anytime soon.
*** This bug has been marked as a duplicate of bug 42145 ***
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-11-20 0:42 UTC | newest]
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2012-12-20 15:36 [Bug regression/55759] New: bogus warning when building drivers/ata/libata-core.c in v3.7 of the linux kernel bp at alien8 dot de
2012-12-20 15:43 ` [Bug regression/55759] " rguenth at gcc dot gnu.org
2012-12-20 16:20 ` bp at alien8 dot de
2012-12-20 16:38 ` markus at trippelsdorf dot de
2012-12-20 18:34 ` markus at trippelsdorf dot de
2013-11-20 0:42 ` law at redhat dot com
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