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* [Bug lto/56578] New: Testcase behaves differently when compiled with LTO
@ 2013-03-09 9:56 d.g.gorbachev at gmail dot com
2013-03-11 10:31 ` [Bug lto/56578] " rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2013-03-09 9:56 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
Bug #: 56578
Summary: Testcase behaves differently when compiled with LTO
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: d.g.gorbachev@gmail.com
Created attachment 29625
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29625
Testcases
The last testcase prints "FAIL". gcc-nm says "no symbols" in the object file
(a.o).
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug lto/56578] Testcase behaves differently when compiled with LTO
2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
@ 2013-03-11 10:31 ` rguenth at gcc dot gnu.org
2013-03-12 0:46 ` d.g.gorbachev at gmail dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-03-11 10:31 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2013-03-11
Ever Confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-11 10:30:13 UTC ---
Hmm, it works for me both with 4.7 and trunk. And
rguenther@murzim:/tmp> gcc-nm-4.7 a.o
00000000 T malloc
rguenther@murzim:/tmp> gcc-nm-4.8 a.o
00000000 T malloc
I'm using GNU ld 2.23.1. Even with gold 2.23.1 it works for me
(that is, 'make' prints three times OK). glibc 2.14.1, x86_64-linux.
Can you elaborate on your configuration?
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug lto/56578] Testcase behaves differently when compiled with LTO
2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
2013-03-11 10:31 ` [Bug lto/56578] " rguenth at gcc dot gnu.org
@ 2013-03-12 0:46 ` d.g.gorbachev at gmail dot com
2013-03-12 9:52 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2013-03-12 0:46 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
--- Comment #2 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2013-03-12 00:46:13 UTC ---
GCC 4.8.0, 4.7.3, 4.6.4; build = host = target = i686-pc-linux-gnu; configured
with "--enable-languages=c,c++ --enable-version-specific-runtime-libs
--disable-nls --disable-shared"; glibc 2.17; recent binutils (GNU ld and gold).
> that is, 'make' prints three times OK
The 4th time (prog3) it prints "FAIL" for me -- free() is from main.c, but
malloc() is from glibc.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug lto/56578] Testcase behaves differently when compiled with LTO
2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
2013-03-11 10:31 ` [Bug lto/56578] " rguenth at gcc dot gnu.org
2013-03-12 0:46 ` d.g.gorbachev at gmail dot com
@ 2013-03-12 9:52 ` rguenth at gcc dot gnu.org
2013-03-12 13:30 ` d.g.gorbachev at gmail dot com
2022-12-01 1:25 ` [Bug lto/56578] Testcase behaves differently when compiled with LTO (builtin for malloc is not getting the right one) pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu.org @ 2013-03-12 9:52 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Status|WAITING |NEW
CC| |hubicka at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
Known to fail| |4.6.4, 4.7.3, 4.8.0
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-12 09:51:51 UTC ---
Thanks. With fixing the size_t issues of the testcase I can reproduce it
on x86_64 as well (original testcase reproduces with -m32).
We could say the bug is in the testcase. Failing is:
gcc-4.8 -B /abuild/rguenther/trunk-g/gcc -flto -c func.c -o a.o
ar --plugin=/abuild/rguenther/trunk-g/gcc/liblto_plugin.so -cr libxxx.a a.o
gcc-4.8 -B /abuild/rguenther/trunk-g/gcc -flto main.c libxxx.a -o prog3
./prog3
FAIL
that's because you are providing an implementation of malloc in libxxx.a a.o
from func.c that does not have the C standards semantics. You have to
compile this module with -fno-builtin-malloc (or -fno-builtins).
Honza: I believe we _should_ tell the linker that we have a definition of
malloc available, even if it is a "builtin". That is, the testcase should
work as it is clearly well-defined on the linker side (setting aside that
GCC might still optimize the result in an unexpected way because it can
rely on malloc/free semantics).
Thus, confirmed as a bug in LTO symtab handling.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug lto/56578] Testcase behaves differently when compiled with LTO
2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
` (2 preceding siblings ...)
2013-03-12 9:52 ` rguenth at gcc dot gnu.org
@ 2013-03-12 13:30 ` d.g.gorbachev at gmail dot com
2022-12-01 1:25 ` [Bug lto/56578] Testcase behaves differently when compiled with LTO (builtin for malloc is not getting the right one) pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: d.g.gorbachev at gmail dot com @ 2013-03-12 13:30 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
--- Comment #4 from Dmitry Gorbachev <d.g.gorbachev at gmail dot com> 2013-03-12 13:30:30 UTC ---
> We could say the bug is in the testcase. Failing is:
[...]
> that's because you are providing an implementation of
> malloc in libxxx.a a.o from func.c that does not have
> the C standards semantics.
The TC is invalid but it is not buggy, gcc-nm could not even find the "malloc"
symbol in a.o
> You have to compile this module with -fno-builtin-malloc
> (or -fno-builtins).
It is not enough to compile just func.c with -fno-builtin(-malloc), as one
might expect. I have to use it for main.c as well.
> GCC might still optimize the result in an unexpected way
> because it can rely on malloc/free semantics
There is a "volatile" modifier in the TC. It should inhibit such optimizations,
I think?
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug lto/56578] Testcase behaves differently when compiled with LTO (builtin for malloc is not getting the right one)
2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
` (3 preceding siblings ...)
2013-03-12 13:30 ` d.g.gorbachev at gmail dot com
@ 2022-12-01 1:25 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-01 1:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56578
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Testcase behaves |Testcase behaves
|differently when compiled |differently when compiled
|with LTO |with LTO (builtin for
| |malloc is not getting the
| |right one)
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I remember seeing another bug that is very similar issue with respect to
builtins.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-12-01 1:25 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2013-03-09 9:56 [Bug lto/56578] New: Testcase behaves differently when compiled with LTO d.g.gorbachev at gmail dot com
2013-03-11 10:31 ` [Bug lto/56578] " rguenth at gcc dot gnu.org
2013-03-12 0:46 ` d.g.gorbachev at gmail dot com
2013-03-12 9:52 ` rguenth at gcc dot gnu.org
2013-03-12 13:30 ` d.g.gorbachev at gmail dot com
2022-12-01 1:25 ` [Bug lto/56578] Testcase behaves differently when compiled with LTO (builtin for malloc is not getting the right one) pinskia at gcc dot gnu.org
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