[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

Buildbots are back to green. It seems like the bug is gone with "gcc (GCC) 
10.2.1 20201125 (Red Hat 10.2.1-9)".

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resolution:  -> fixed
stage: needs patch -> resolved
status: open -> closed

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

I reported the issue to Fedora: 
https://bugzilla.redhat.com/show_bug.cgi?id=1891657

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

> Yeah, now try to compile with LTO and CFLAGS='-O0'

Using LTO:

* "-O1 -finline-functions -finline-small-functions -fpartial-inlining" 
reproduces the issue.
* "-O1" does not reproduce the issue.

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

> With LTO, compile.o requires an undefined _Py_Mangle symbol:


Yeah, now try to compile with LTO and CFLAGS='-O0'

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

With LTO, compile.o requires an undefined _Py_Mangle symbol:

$ gcc -pthread -c -DNDEBUG -fwrapv -O3 -std=c99 -fvisibility=hidden -flto 
-I./Include/internal  -I. -I./Include -DPy_BUILD_CORE -o Python/compile.o 
Python/compile.c; nm Python/compile.o | grep _Py_Mangle

 U _Py_Mangle


Without LTO, compile.o defines _Py_Mangle symbol:

$ gcc -pthread -c -DNDEBUG -fwrapv -O3 -std=c99 -fvisibility=hidden 
-I./Include/internal  -I. -I./Include -DPy_BUILD_CORE -o Python/compile.o 
Python/compile.c; nm Python/compile.o | grep _Py_Mangle

3c20 T _Py_Mangle

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

I reproduced the bug on Fedora 32 with gcc-10.2.1-6.fc32.x86_64 (new) but I 
failed to reproduce with gcc-10.2.1-1.fc32.x86_64 (old, before I upgraded GCC). 
So it's a regression of gcc-10.2.1-6.fc32.x86_64 package.

The package contains multiple downstream patches:

   https://src.fedoraproject.org/rpms/gcc/tree/f32

Commands used to reproduce the issue:

   export MAKEFLAGS=-j10
   ./configure --with-lto 
   make

Extract of my Makefile:

OPT=-DNDEBUG -g -fwrapv -O3 -Wall
BASECFLAGS=  -Wno-unused-result -Wsign-compare
CONFIGURE_CFLAGS_NODIST= -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g -std=c99 -Wextra -Wno-unused-result 
-Wno-unused-parameter -Wno-missing-field-initializers 
-Werror=implicit-function-declaration -fvisibility=hidden
CONFIGURE_LDFLAGS_NODIST= -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g

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[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[STINNER Victor]

STINNER Victor  added the comment:

> I have been trying to diagnose this failure:
> https://buildbot.python.org/all/#/builders/271/builds/710/steps/3/logs/stdio

This is the "AMD64 Fedora Stable LTO 3.x" worker. The latest successful build 
was build 684, finished 6 days ago. test.pythoninfo of build 684:

CC.version: gcc (GCC) 10.2.1 20200723 (Red Hat 10.2.1-1)
platform.libc_ver: glibc 2.31
platform.platform: Linux-5.8.14-200.fc32.x86_64-x86_64-with-glibc2.31
sys.version: 3.10.0a1+ (heads/master:c0f22fb8b3, Oct 21 2020, 00:02:36)  [GCC 
10.2.1 20200723 (Red Hat 10.2.1-1)]
sysconfig[CCSHARED]: -fPIC
sysconfig[CC]: gcc -pthread
sysconfig[CFLAGS]: -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 
-Wall
sysconfig[OPT]: -DNDEBUG -g -fwrapv -O3 -Wall
sysconfig[PY_CFLAGS]: -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 
-Wall
sysconfig[PY_CFLAGS_NODIST]: -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g -std=c99 -Wextra -Wno-unused-result 
-Wno-unused-parameter -Wno-missing-field-initializers 
-Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal
sysconfig[PY_CORE_LDFLAGS]: -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g
sysconfig[PY_LDFLAGS_NODIST]: -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g
sysconfig[PY_STDMODULE_CFLAGS]: -Wno-unused-result -Wsign-compare -DNDEBUG -g 
-fwrapv -O3 -Wall -flto -fuse-linker-plugin -ffat-lto-objects 
-flto-partition=none -g -std=c99 -Wextra -Wno-unused-result 
-Wno-unused-parameter -Wno-missing-field-initializers 
-Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal 
-I. -I./Include


It started to fail at October 21 (build 685). At 2020-10-21, GCC package was 
upgraded from version 10.2.1-1 to 10.2.1-5 to gcc-10.2.1-5 according to 
/var/log/dnf.log:

2020-10-21T06:58:01-0400 SUBDEBUG drpm: spawned 2243855: /usr/bin/applydeltarpm 
-a x86_64 
/var/cache/dnf/updates-b3cb4614b6495970/packages/gcc-10.2.1-1.fc32_10.2.1-5.fc32.x86_64.drpm
 /var/cache/dnf/updates-b3cb4614b6495970/packages/gcc-10.2.1-5.fc32.x86_64.rpm

Package changelog between 10.2.1-1 and 10.2.1-5:
---
* Mon Oct 05 2020 Jakub Jelinek  10.2.1-5
- update from releases/gcc-10 branch
  - PRs bootstrap/97163, bootstrap/97183, c++/96994, c++/97145, c++/97195,
fortran/93423, fortran/95614, fortran/96041, gcov-profile/64636,
gcov-profile/96913, gcov-profile/97069, gcov-profile/97193,
libstdc++/94160, libstdc++/94681, libstdc++/96803, libstdc++/97101,
libstdc++/97167, middle-end/95464, middle-end/97054, middle-end/97073,
preprocessor/96935, target/71233, target/96683, target/96795,
target/96827, target/97166, target/97184, target/97231, target/97247,
tree-optimization/96979, tree-optimization/97053

* Wed Sep 16 2020 Jakub Jelinek  10.2.1-4
- update from releases/gcc-10 branch
  - PRs bootstrap/96203, c++/95164, c++/96862, c++/96901, d/96157, d/96924,
debug/93865, debug/94235, debug/96729, fortran/94690, fortran/95109,
fortran/95398, fortran/95882, fortran/96859, libstdc++/71960,
libstdc++/92978, libstdc++/96766, libstdc++/96851, lto/94311,
middle-end/87256, middle-end/96369, target/85830, target/94538,
target/96357, target/96551, target/96574, target/96744, target/96808,
target/97028, tree-optimization/88240, tree-optimization/96349,
tree-optimization/96370, tree-optimization/96514,
tree-optimization/96522, tree-optimization/96579,
tree-optimization/96597, tree-optimization/96820,
tree-optimization/96854, tree-optimization/97043
- fix up ARM target attribute/pragma handling (#1875814, PR target/96939)
- don't ICE on sp clobbers with -mincoming-stack-boundary=2 on ia32
  (#1862029, PR target/97032)

* Wed Aug 26 2020 Jakub Jelinek  10.2.1-3
- update from releases/gcc-10 branch
  - PRs c++/95428, c++/96082, c++/96106, c++/96164, c++/96199, c++/96497,
c/96545, c/96549, c/96571, d/96250, d/96254, d/96301, debug/96354,
fortran/93553, fortran/96312, fortran/96486, ipa/95320, ipa/96291,
ipa/96482, libstdc++/89760, libstdc++/95749, libstdc++/96303,
libstdc++/96484, libstdc++/96718, lto/95362, lto/95548,
middle-end/96426, middle-end/96459, target/93897, target/95450,
target/96191, target/96243, target/96446, target/96493, target/96506,
target/96525, target/96530, target/96536, target/96562, target/96682,
tree-optimization/96483, tree-optimization/96535,
tree-optimization/96722, tree-optimization/96730,
tree-optimization/96758
- mangle some further symbols needed for debug info during early dwarf
  (#1862029, PR debug/96690)
- during %check perform tests whether annobin is usable with the newly built
  compiler or whether it might need to be rebuilt
- disable graphite for ELN

* Tue Aug 04 2020 Jakub Jelinek  10.2.1-2
- update from releases/gcc-10 branch
  - PRs c++/95591, c++/95599, 

[issue42164] Python fails to compile in the Fedora Stable LTO buildbots

[Pablo Galindo Salgado]

New submission from Pablo Galindo Salgado :

I have been trying to diagnose this failure:

https://buildbot.python.org/all/#/builders/271/builds/710/steps/3/logs/stdio

it happens on these buildbots:

x86_64 fedora stable
ppc64le fedora stable (so 32 now)

It seems that CPython cannot be compiled with --with-lto regardless of the 
version:

https://buildbot.python.org/all/#/builders/336/builds/2145
https://buildbot.python.org/all/#/builders/426/builds/641
https://buildbot.python.org/all/#/builders/294/builds/986

This seems to indicate that something has changed in these buildbots somehow. 
Maybe the gcc installation is broken?

In my investigation, it seems that Python/compile.o is miscompiled.For example

FEDORA BUILDBOT with LTO:

[buildbot@python-builder2-rawhide cpython]$ nm Python/compile.o  | grep 
_Py_Mangle
In function ‘assemble_lnotab’,
inlined from ‘assemble_emit’ at Python/compile.c:5696:25,
inlined from ‘assemble’ at Python/compile.c:6038:18:
Python/compile.c:5650:19: warning: writing 1 byte into a region of size 0 
[-Wstringop-overflow=]
 5650 | *lnotab++ = k;
  |   ^
 U _Py_Mangle


MY ARCH LINUX SYSTEM:

❯ nm Python/compile.o  | grep _Py_Mangle
 T _Py_Mangle

It seems that the _Py_Mangle is not included in the object file. Is this a gcc 
bug? I have not been able to diagnose exactly where does this problem. It seems 
that the gcc version is "10.2.1" but I can correctly build CPython with LTO in 
my arch Linux machine with gcc 10.2.0.

Given that these are stable buildbots, could you investigate what is going on 
or report this to the gcc folks ar RedHat/Fedora? 



More interesting data:

Compiling with -O0 does not have a problem, but doing it with -O3 does.

With -O0:

[buildbot@python-builder2-rawhide cpython]$ nm Python/compile.o  | grep 
_Py_Mangle
 T _Py_Mangle

With -O3:

[buildbot@python-builder2-rawhide cpython]$ nm Python/compile.o  | grep 
_Py_Mangle
 U _Py_Mangle

--
components: Build
messages: 379696
nosy: cstratak, hroncok, pablogsal, petr.viktorin, vstinner
priority: normal
severity: normal
stage: needs patch
status: open
title: Python fails to compile in the Fedora Stable LTO buildbots
type: compile error
versions: Python 3.10, Python 3.8, Python 3.9

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