* [Bug tree-optimization/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
@ 2021-01-12 8:11 ` rguenth at gcc dot gnu.org
2021-01-12 8:22 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-01-12 8:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |tree-optimization
Ever confirmed|0 |1
Known to fail| |11.0
Keywords| |wrong-code
Last reconfirmed| |2021-01-12
Status|UNCONFIRMED |NEW
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed with -O1 on trunk. We're losing the m initialization.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug tree-optimization/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
2021-01-12 8:11 ` [Bug tree-optimization/98630] " rguenth at gcc dot gnu.org
@ 2021-01-12 8:22 ` rguenth at gcc dot gnu.org
2021-01-12 8:26 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-01-12 8:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Vanishes in CCP - I'll see what happens.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug tree-optimization/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
2021-01-12 8:11 ` [Bug tree-optimization/98630] " rguenth at gcc dot gnu.org
2021-01-12 8:22 ` rguenth at gcc dot gnu.org
@ 2021-01-12 8:26 ` rguenth at gcc dot gnu.org
2021-01-12 8:29 ` [Bug c/98630] " rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-01-12 8:26 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |INVALID
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so the issue is that 'm' goes out of scope before the goto p; and this
goto skips the initialization. This means this is an invalid testcase unless
somehow C makes this well-defined.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (2 preceding siblings ...)
2021-01-12 8:26 ` rguenth at gcc dot gnu.org
@ 2021-01-12 8:29 ` rguenth at gcc dot gnu.org
2021-01-12 8:50 ` k.even-mendoza at imperial dot ac.uk
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From: rguenth at gcc dot gnu.org @ 2021-01-12 8:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |NEW
Assignee|rguenth at gcc dot gnu.org |unassigned at gcc dot gnu.org
Component|tree-optimization |c
Resolution|INVALID |---
Keywords|wrong-code |diagnostic
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
And -Wall says correctly
t.c: In function ‘j’:
t.c:16:14: warning: ‘m’ is used uninitialized [-Wuninitialized]
16 | ***o = 0;
| ~~~~~^~~
but we fail to diagnose that the goto crosses the initialization. Re-opening
for that to improve.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
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2021-01-12 8:29 ` [Bug c/98630] " rguenth at gcc dot gnu.org
@ 2021-01-12 8:50 ` k.even-mendoza at imperial dot ac.uk
2021-01-12 8:51 ` k.even-mendoza at imperial dot ac.uk
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From: k.even-mendoza at imperial dot ac.uk @ 2021-01-12 8:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #5 from Karine EM <k.even-mendoza at imperial dot ac.uk> ---
This is an automatically reduced program. If GCC will give the Wuninitialized
warning I can reduce the original program again, taking it into account.
I attached the long program in case you find it helpful. It also ends with
Seg-Fault for gcc-10 but not with gcc-7, gcc-8, gcc-9 for example. G++-10
doesn't give uninitialized warning on the long program.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (4 preceding siblings ...)
2021-01-12 8:50 ` k.even-mendoza at imperial dot ac.uk
@ 2021-01-12 8:51 ` k.even-mendoza at imperial dot ac.uk
2021-01-12 10:08 ` jakub at gcc dot gnu.org
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From: k.even-mendoza at imperial dot ac.uk @ 2021-01-12 8:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #6 from Karine EM <k.even-mendoza at imperial dot ac.uk> ---
Created attachment 49945
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49945&action=edit
Original large code that caused Seg-fault in GCC-10
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (5 preceding siblings ...)
2021-01-12 8:51 ` k.even-mendoza at imperial dot ac.uk
@ 2021-01-12 10:08 ` jakub at gcc dot gnu.org
2021-01-12 10:16 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-01-12 10:08 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Karine EM from comment #6)
> Created attachment 49945 [details]
> Original large code that caused Seg-fault in GCC-10
Can you please preprocess this (so that it doesn't contain csmith.h include)?
Thanks.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (6 preceding siblings ...)
2021-01-12 10:08 ` jakub at gcc dot gnu.org
@ 2021-01-12 10:16 ` jakub at gcc dot gnu.org
2021-01-12 10:33 ` rguenth at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-01-12 10:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
For goto crossing initialization, C++ makes it a hard error and C only has a
non-default warning (not even in -W), -Wjump-misses-init included in
-Wc++-compat.
As can be seen on:
int
foo (void)
{
goto a;
int b = 1;
a:
b++;
return b;
}
int
bar (void)
{
goto a;
{
int b = 1;
a:
b++;
return b;
}
}
int
baz (void)
{
{
int b = 1;
if (1)
;
else
{
a:
b++;
return b;
}
}
goto a;
}
with g++ or gcc -Wjump-misses-init
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (7 preceding siblings ...)
2021-01-12 10:16 ` jakub at gcc dot gnu.org
@ 2021-01-12 10:33 ` rguenth at gcc dot gnu.org
2021-01-12 10:40 ` jakub at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-01-12 10:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
Given we now place CLOBBERS at scope ends even for C code (which is why we
"miscompile" the reduced testcase) doesn't it make sense to at least include
-Wjump-misses-init into -W[extra] or even -Wall?
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (8 preceding siblings ...)
2021-01-12 10:33 ` rguenth at gcc dot gnu.org
@ 2021-01-12 10:40 ` jakub at gcc dot gnu.org
2021-01-12 10:43 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-01-12 10:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Maybe, but I think it is too late to do it now for GCC 11, it will take time
before we figure out how many projects will be affected by that.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (9 preceding siblings ...)
2021-01-12 10:40 ` jakub at gcc dot gnu.org
@ 2021-01-12 10:43 ` jakub at gcc dot gnu.org
2021-01-12 14:34 ` k.even-mendoza at imperial dot ac.uk
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From: jakub at gcc dot gnu.org @ 2021-01-12 10:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The reason why C++ has it as hard error is I think object
construction/destruction, in C the warning is for code to be portable to C++,
in plain C it is all about making sure variables are initialized, which users
can do correctly even if they cross variable initialization.
So in C there is nothing wrong per se on the crossing, just the warning can
help if -Wuninitialized or -Wmaybe-uninitialized has false negatives as in this
case.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (10 preceding siblings ...)
2021-01-12 10:43 ` jakub at gcc dot gnu.org
@ 2021-01-12 14:34 ` k.even-mendoza at imperial dot ac.uk
2021-01-12 14:39 ` jakub at gcc dot gnu.org
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From: k.even-mendoza at imperial dot ac.uk @ 2021-01-12 14:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #12 from Karine EM <k.even-mendoza at imperial dot ac.uk> ---
Yes, I could do that (comment #7). But I reduce manually the program and the
problem was indeed the scenario in comment #8 (not between functions, only
different blocks, but I assume it is pretty much the same).
If you add a new warning also to GCC at some point, it will be useful.
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (11 preceding siblings ...)
2021-01-12 14:34 ` k.even-mendoza at imperial dot ac.uk
@ 2021-01-12 14:39 ` jakub at gcc dot gnu.org
2021-01-12 14:42 ` k.even-mendoza at imperial dot ac.uk
2021-01-12 14:44 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-01-12 14:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Then -Wjump-misses-init should warn even on the unreduced testcase...
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (12 preceding siblings ...)
2021-01-12 14:39 ` jakub at gcc dot gnu.org
@ 2021-01-12 14:42 ` k.even-mendoza at imperial dot ac.uk
2021-01-12 14:44 ` jakub at gcc dot gnu.org
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From: k.even-mendoza at imperial dot ac.uk @ 2021-01-12 14:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #14 from Karine EM <k.even-mendoza at imperial dot ac.uk> ---
I did compile it that way:
> gcc-10 -w -O2 r.c -pedantic -Wall -Wextra
but got no warnings at all. Should I add any flag?
Thanks!
^ permalink raw reply [flat|nested] 16+ messages in thread
* [Bug c/98630] Seg-fault when using a goto after condition (if)
2021-01-11 22:48 [Bug c/98630] New: Seg-fault when using a goto after condition (if) k.even-mendoza at imperial dot ac.uk
` (13 preceding siblings ...)
2021-01-12 14:42 ` k.even-mendoza at imperial dot ac.uk
@ 2021-01-12 14:44 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-01-12 14:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98630
--- Comment #15 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Yes, that -Wjump-misses-init or -Wc++-compat.
^ permalink raw reply [flat|nested] 16+ messages in thread