ARM Raspbian 3.x fails to build _testcapi extension: undefined symbol: __atomic_fetch_or_8 #109054

vstinner · 2023-09-07T04:23:35Z

I supposed that the build error is related to Modules/_testcapi/pyatomic.c and Include/cpython/pyatomic.h.

"Raspbian is a free operating system based on Debian optimized for the Raspberry Pi hardware."

Buildbot worker says: "Raspberry Pi 4 B running Raspbian (Bullseye 11.x)."

test.pythoninfo:

CC.version: gcc (Raspbian 10.2.1-6+rpi1) 10.2.1 20210110
platform.architecture: 32bit ELF
platform.libc_ver: glibc 2.31
platform.platform: Linux-6.1.21-v8+-aarch64-with-glibc2.31
sysconfig[PY_CFLAGS]: -fno-strict-overflow -DNDEBUG -g -O3 -Wall -UNDEBUG
sysconfig[PY_CFLAGS_NODIST]: -std=c11 -Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal
sysconfig[PY_STDMODULE_CFLAGS]: -fno-strict-overflow -DNDEBUG -g -O3 -Wall -UNDEBUG -std=c11 -Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal -I. -I./Include

Logs:

gcc -pthread -shared      Modules/_testcapimodule.o Modules/_testcapi/vectorcall.o Modules/_testcapi/vectorcall_limited.o Modules/_testcapi/heaptype.o Modules/_testcapi/abstract.o Modules/_testcapi/unicode.o Modules/_testcapi/dict.o Modules/_testcapi/getargs.o Modules/_testcapi/datetime.o Modules/_testcapi/docstring.o Modules/_testcapi/mem.o Modules/_testcapi/watchers.o Modules/_testcapi/long.o Modules/_testcapi/float.o Modules/_testcapi/structmember.o Modules/_testcapi/exceptions.o Modules/_testcapi/code.o Modules/_testcapi/buffer.o Modules/_testcapi/pyatomic.o Modules/_testcapi/pyos.o Modules/_testcapi/immortal.o Modules/_testcapi/heaptype_relative.o Modules/_testcapi/gc.o   -o Modules/_testcapi.cpython-313-arm-linux-gnueabihf.so
[ERROR] _testcapi failed to import: /var/lib/buildbot/workers/3.x.gps-raspbian.nondebug/build/build/lib.linux-aarch64-3.13/_testcapi.cpython-313-arm-linux-gnueabihf.so: undefined symbol: __atomic_fetch_or_8
The necessary bits to build these optional modules were not found:
_tkinter              _uuid                                    
To find the necessary bits, look in configure.ac and config.log.

Following modules built successfully but were removed because they could not be imported:
_testcapi                                                      

Checked 107 modules (31 built-in, 72 shared, 1 n/a on linux-aarch64, 0 disabled, 2 missing, 1 failed on import)

logs: https://buildbot.python.org/all/#/builders/424/builds/4849

cc @colesbury @gpshead

Linked PRs

The text was updated successfully, but these errors were encountered:

vstinner · 2023-09-07T04:29:24Z

Maybe Python should be linked to -latomic. Old GCC discussions:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81358
"I think we should generally link libatomic with --as-needed by default: https://gcc.gnu.org/legacy-ml/gcc-patches/2013-11/msg02605.html

vstinner · 2023-09-07T04:32:54Z

Another example:

vstinner · 2023-09-07T04:41:34Z

Build 4788: 39 tests failed: https://buildbot.python.org/all/#/builders/424/builds/4788 -- this one added pyatomic.h and related _testcapi tests
Build 4787: test_concurrent_futures.test_shutdown failed: https://buildbot.python.org/all/#/builders/424/builds/4787

I confirm that this regression comes from the commit 2bd960b.

colesbury · 2023-09-07T13:33:12Z

I'm on vacation this week, but I'll have some time to look at this this evening.

vstinner · 2023-09-07T16:19:03Z

I never heard about Raspbian before. I was curious about it, so I added platform.freedesktop_os_release() to test.pythoninfo :-)

platform.freedesktop_os_release[ID]: raspbian
platform.freedesktop_os_release[NAME]: Raspbian GNU/Linux
platform.freedesktop_os_release[VERSION]: 11 (bullseye)
platform.freedesktop_os_release[VERSION_CODENAME]: bullseye
platform.freedesktop_os_release[VERSION_ID]: 11

Check if <cpython/pyatomic.h> needs to be linked to libatomic.

Fix building the _testcapi extension on ARM Raspbian which requires linking to libatomic when <cpython/pyatomic.h> is used. * configure checks if programs using <cpython/pyatomic.h> need to be linked to libatomic. * Add LIBATOMIC variable to Makefile. * _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>.

Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint8() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>.

Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint8() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. Building the _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>.

colesbury · 2023-09-08T01:38:48Z

From @vstinner's comments and playing with https://gcc.godbolt.org/, it looks like the 8 byte (64-bit) use library support with the default compiler options on this platform. GCC doesn't need the library support if you target -march=armv7-a (the ARMv7-A and ARMv7-R profiles support the ldrexd "double-word" exclusive load).

Some random other things that I learned, but are probably not important:

Raspbian is now called Raspberry Pi OS
The Raspberry Pi Model B's have used a 64-bit CPUs (armv8-a) since ~2016, but the Raspbian/Raspberry Pi OS was 32-bit only until 2022 and it seems like 32-bit OS is still the most commonly used

Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint64() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. Building the _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>.

vstinner · 2023-09-08T07:32:29Z

From @vstinner's comments and playing with https://gcc.godbolt.org/, it looks like the 8 byte (64-bit) use library support with the default compiler options on this platform. GCC doesn't need the library support if you target -march=armv7-a (the ARMv7-A and ARMv7-R profiles support the ldrexd "double-word" exclusive load).

It's nice if libatomic can be omitted depending on the compiler and compiler flags, but I would like to cover all cases :-) We should detect and add -latomic when needed.

ayappanec · 2023-09-08T11:19:06Z

AIX also fails to build because of this problem.
Modules/ld_so_aix gcc -pthread -bI:Modules/python.exp Modules/_testcapimodule.o Modules/_testcapi/vectorcall.o Modules/_testcapi/vectorcall_limited.o Modules/_testcapi/heaptype.o Modules/_testcapi/abstract.o Modules/_testcapi/unicode.o Modules/_testcapi/dict.o Modules/_testcapi/getargs.o Modules/_testcapi/datetime.o Modules/_testcapi/docstring.o Modules/_testcapi/mem.o Modules/_testcapi/watchers.o Modules/_testcapi/long.o Modules/_testcapi/float.o Modules/_testcapi/structmember.o Modules/_testcapi/exceptions.o Modules/_testcapi/code.o Modules/_testcapi/buffer.o Modules/_testcapi/pyatomic.o Modules/_testcapi/pyos.o Modules/_testcapi/immortal.o Modules/_testcapi/heaptype_relative.o Modules/_testcapi/gc.o -o Modules/_testcapi.cpython-313.so
ld: 0711-327 WARNING: Entry point not found: PyInit__testcapi.cpython-313
ld: 0711-317 ERROR: Undefined symbol: .__atomic_fetch_or_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_fetch_and_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_load_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_store_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_exchange_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_compare_exchange_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_fetch_add_8

Need -latomic to be passed. I see MODULE__TESTCAPI_LDFLAGS variable in the generated Makefile but not populated with anything

vstinner · 2023-09-08T11:20:58Z

AIX also fails to build because of this problem.

Can you try my PR? Does it fix your issue?

ayappanec · 2023-09-08T11:34:17Z

AIX also fails to build because of this problem.

Can you try my PR? Does it fix your issue?

https://github.com/vstinner/cpython/tree/configure_libatomic
It still failed with the same error

The config.log has this

configure:27770: checking whether libatomic is needed by <pyatomic.h>
configure:27815: gcc -pthread -o conftest -I. -I./Include conftest.c -lintl -ldl >&5
conftest.c:422: warning: "PY_BUILTIN_HASHLIB_HASHES" redefined
422 | #define PY_BUILTIN_HASHLIB_HASHES "md5,sha1,sha2,sha3,blake2"
|
conftest.c:421: note: this is the location of the previous definition
421 | #define PY_BUILTIN_HASHLIB_HASHES /**/
|
ld: 0711-317 ERROR: Undefined symbol: .__atomic_fetch_or_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_load_8
ld: 0711-317 ERROR: Undefined symbol: .__atomic_store_8
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
collect2: error: ld returned 8 exit status
configure:27815: $? = 1
configure: program exited with status 1

ayappanec · 2023-09-08T12:21:23Z

In AIX, only the 32bit build fails. 64bit build doesn't require -latomic looks like.

vstinner · 2023-09-08T12:51:50Z

The config.log has this

What does the configure say? Does it say checking whether libatomic is needed by <pyatomic.h>... yes?

Also, check if make links _testcapi with -latomic. Or check grep '_TESTCAPI_.*=' Makefile command to see if you have -latomic in MODULE__TESTCAPI_LDFLAGS.

ayappanec · 2023-09-08T12:53:14Z

https://github.com/vstinner/cpython/blob/configure_libatomic/configure#L27834
This line has some typo error I guess.

ayappanec · 2023-09-08T12:53:48Z

LIBATOMIC=${LIBATOMIC-"-latomic"}

ayappanec · 2023-09-08T12:55:59Z

The config.log has this

What does the configure say? Does it say checking whether libatomic is needed by <pyatomic.h>... yes?

Also, check if make links _testcapi with -latomic. Or check grep '_TESTCAPI_.*=' Makefile command to see if you have -latomic in MODULE__TESTCAPI_LDFLAGS.

MODULE__TESTCAPI_LDFLAGS is never populated with $LIBATOMIC, even though "MODULE__TESTCAPI_STATE=yes"

Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint64() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. Building the _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>. Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

vstinner · 2023-09-08T12:58:39Z

This line has some typo error I guess.

LIBATOMIC=${LIBATOMIC-"-latomic"} is a dark spell of @erlend-aasland.

Sorry but I don't understand you test. Please:

Apply my latest PR (I just updated it)
Run ./configure
Check checking whether libatomic is needed by <pyatomic.h> line in configure output. Is it yes or not?
Check MODULE__TESTCAPI_LDFLAGS in Makefile: what is the variable value?

It's not clear to me if you ran your test on 32-bit or 64-bit AIX.

ayappanec · 2023-09-08T13:19:06Z

This line has some typo error I guess.

LIBATOMIC=${LIBATOMIC-"-latomic"} is a dark spell of @erlend-aasland.

Sorry but I don't understand you test. Please:

Apply my latest PR (I just updated it)

Run ./configure

Check checking whether libatomic is needed by <pyatomic.h> line in configure output. Is it yes or not?

Check MODULE__TESTCAPI_LDFLAGS in Makefile: what is the variable value?

It's not clear to me if you ran your test on 32-bit or 64-bit AIX.

I did a fresh
git clone https://github.com/vstinner/cpython
cd cpython
git checkout configure_libatomic
./configure

checking whether libatomic is needed by <pyatomic.h>, the result is yes
But "MODULE__TESTCAPI_LDFLAGS= " is still empty in Makefile.

It's a 32bit build. In AIX ,the default build environment is 32bit.

64bit build in AIX works as it doesn't require -latomic .

ayappanec · 2023-09-08T13:31:50Z

LIBATOMIC=""
LIBATOMIC=${LIBATOMIC-"-latomic"}
echo $LIBATOMIC

This scenario never works

ayappanec · 2023-09-08T13:59:40Z

LIBATOMIC=${LIBATOMIC:-"-latomic"} will work instead.

vstinner · 2023-09-08T15:08:49Z

I fixed (again ;-)) my PR. Please test it.

The problem is that LIBATOMIC=${LIBATOMIC-"-latomic"} does nothing if the LIBATOMIC variable is already defined. And I defined it to an empty string with LIBATOMIC="".

ayappanec · 2023-09-08T15:47:09Z

I fixed (again ;-)) my PR. Please test it.

The problem is that LIBATOMIC=${LIBATOMIC-"-latomic"} does nothing if the LIBATOMIC variable is already defined. And I defined it to an empty string with LIBATOMIC="".

It works now.

vstinner · 2023-09-08T16:04:08Z

It works now.

Thanks for testing it!

Fix building the _testcapi extension on Linux AArch64 which requires linking to libatomic when <cpython/pyatomic.h> is used: the _Py_atomic_or_uint64() function requires libatomic __atomic_fetch_or_8() on this platform. The configure script now checks if linking to libatomic is needed and generates a new LIBATOMIC variable used to build the _testcapi extension. Building the _testcapi extension now uses the LIBATOMIC variable in its LDFLAGS, since Modules/_testcapi/pyatomic.c uses <cpython/pyatomic.h>. Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

vstinner · 2023-09-08T21:18:13Z

Fixed by 1f7e421

configure no longer uses libatomic by default when Python is cross-compiled. The LIBATOMIC variable can be set manually in this case: ./configure LIBATOMIC="-latomic" (...)

vstinner added a commit to vstinner/cpython that referenced this issue Sep 7, 2023

pythongh-109054: configure adds libatomic if needed

b353cff

Check if <cpython/pyatomic.h> needs to be linked to libatomic.

bedevere-bot mentioned this issue Sep 7, 2023

gh-109054: configure checks if libatomic is needed #109101

Merged

vstinner closed this as completed Sep 8, 2023

bedevere-bot mentioned this issue Sep 10, 2023

gh-109054: Don't use libatomic on cross-compilation #109211

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pythongh-109054: Document configue options

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gh-109054: Document configure variables #109224

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pythongh-109054: Document configue variables

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pythongh-109054: Document configue variables

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Build Error on RISC-V: undefined reference to `__atomic_exchange_1' #112779

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ARM Raspbian 3.x fails to build _testcapi extension: undefined symbol: __atomic_fetch_or_8 #109054

ARM Raspbian 3.x fails to build _testcapi extension: undefined symbol: __atomic_fetch_or_8 #109054

vstinner commented Sep 7, 2023 •

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ARM Raspbian 3.x fails to build _testcapi extension: undefined symbol: __atomic_fetch_or_8 #109054

ARM Raspbian 3.x fails to build _testcapi extension: undefined symbol: __atomic_fetch_or_8 #109054

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vstinner commented Sep 7, 2023 • edited by bedevere-bot

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