[PATCH] Link static C++ tests against libatomic.a if needed

Tue May 5 21:15:50 GMT 2026

On 05/05/26 18:10, H.J. Lu wrote:
> On Wed, May 6, 2026 at 4:57 AM Adhemerval Zanella Netto
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 05/05/26 17:49, H.J. Lu wrote:
>>> On Tue, May 5, 2026 at 8:36 PM Adhemerval Zanella Netto
>>> <adhemerval.zanella@linaro.org> wrote:
>>>>
>>>>
>>>>
>>>> On 05/05/26 09:33, H.J. Lu wrote:
>>>>> On Tue, May 5, 2026 at 8:27 PM Adhemerval Zanella Netto
>>>>> <adhemerval.zanella@linaro.org> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 04/05/26 22:50, H.J. Lu wrote:
>>>>>>> On Tue, May 5, 2026 at 9:42 AM Sam James <sam@gentoo.org> wrote:
>>>>>>>>
>>>>>>>> "H.J. Lu" <hjl.tools@gmail.com> writes:
>>>>>>>>
>>>>>>>>> On Mon, May 4, 2026 at 10:33 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>> Define cxx-static-link-libatomic to -latomic if DT_NEEDED entries in
>>>>>>>>>> libstdc++.so include libatomic.so.  Update link-extra-libs-static to
>>>>>>>>>> include $(cxx-static-link-libatomic) if -lstdc++ is used.
>>>>>>>>>>
>>>>>>>>>> Tested with sparcv8-linux-gnu-leon3 and sparcv9-linux-gnu using
>>>>>>>>>> uild-many-glibcs.py.  This fixes BZ #34121.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> FWIW, sparc g++ does pass -latomic_asneeded to ld.  But glibc tests
>>>>>>>>> are built with -nostdlib -nostartfiles using gcc, not g++.
>>>>>>>>
>>>>>>>> https://inbox.sourceware.org/gcc-patches/CACb0b4m+ex47Tpyp1qvW9+0p4onyEvsfXeXE_4zZrteMO5q5EQ@mail.gmail.com/
>>>>>>>>
>>>>>>>> I don't remember what happened with that, there were a few issues with
>>>>>>>> the libatomic autolinking so I lost track.
>>>>>>>
>>>>>>> One way to fix the gcc is to create libstdc++.a as linker script, similar to
>>>>>>>
>>>>>>> [hjl@gnu-tgl-3 x86-glibc]$ cat /usr/lib64/libm.a
>>>>>>> /* GNU ld script
>>>>>>> */
>>>>>>> OUTPUT_FORMAT(elf64-x86-64)
>>>>>>> GROUP ( /usr/lib64/libm-2.43.a /usr/lib64/libmvec.a )
>>>>>>> [hjl@gnu-tgl-3 x86-glibc]$
>>>>>>>
>>>>>>> to include libatomic.a in libstdc++.a if needed.  But I don't know if it works
>>>>>>> everywhere.
>>>>>>>
>>>>>>
>>>>>> It seems gcc-16 has another issue, it also fails on building glibc after a bootstrap
>>>>>> with build-many-glibcs.py with:
>>>>>>
>>>>>> [..-m32 -mlong-double-128 -mcpu=v9 -o /home/azanella/Projects/glibc/build/sparcv9-linux-gnu-gcc16/support/links-dso-program -pie  -Wl,-O1 -nostdlib -nostartfiles [...]
>>>>>> [...]/sparc64-linux-gnu/sparc64-glibc-linux-gnu/bin/ld: [...]/sparc64-linux-gnu/bin/../lib/gcc/sparc64-glibc-linux-gnu/16.1.1/../../../../sparc64-glibc-linux-gnu/lib/../lib/libstdc++.so: undefined reference to `__atomic_fetch_add_4@LIBATOMIC_1.0'
>>>>>> [...]//sparc64-glibc-lisparc64-linux-gnunux-gnu/bin/ld: [...]/sparc64-linux-gnu/bin/../lib/gcc/sparc64-glibc-linux-gnu/16.1.1/../../../../sparc64-glibc-linux-gnu/lib/../lib/libstdc++.so: undefined reference to `__atomic_fetch_sub_4@LIBATOMIC_1.0'
>>>>>>
>>>>>> And dumping the linker invocation, it shows another issue:
>>>>>>
>>>>>> ld: warning: libatomic.so.1, needed by [...]/sparc64-linux-gnu/bin/../lib/gcc/sparc64-glibc-linux-gnu/16.1.1/../../../../sparc64-glibc-linux-gnu/lib/../lib/libstdc++.so, not found (try using -rpath or -rpath-link)
>>>>>
>>>>> Which version of binutils are you using?  Binutils master branch works
>>>>> for me for sparc64-glibc-linux-gnu.
>>>>
>>>> It is a pretty recent one:
>>>>
>>>> $ ./bin/sparc64-glibc-linux-gnu-ld -v
>>>> GNU ld (GNU Binutils) 2.46.0.20260504
>>>
>>> This shouldn't happen since __atomic_fetch_sub_4 is only referenced
>>> inside of libstdc++.so.  Why can't ld find libatomic.so.1? Mine has
>>>
>>> [hjl@gnu-zen4-1 lib]$ pwd
>>> /export/build/gnu/tools-build/glibc-many/install/compilers/sparc64-linux-gnu/sparc64-glibc-linux-gnu/lib
>>> [hjl@gnu-zen4-1 lib]$ ls
>>> ldscripts              libgomp.la        libstdc++exp.a
>>> libatomic.a            libgomp.so        libstdc++exp.la
>>> libatomic_asneeded.a   libgomp.so.1      libstdc++fs.a
>>> libatomic_asneeded.so  libgomp.so.1.0.0  libstdc++fs.la
>>> libatomic.la           libgomp.spec      libstdc++.la
>>> libatomic.so           libitm.a          libstdc++.modules.json
>>> libatomic.so.1         libitm.la         libstdc++.so
>>> libatomic.so.1.2.0     libitm.so         libstdc++.so.6
>>> libgcc_s_asneeded.so   libitm.so.1       libstdc++.so.6.0.35
>>> libgcc_s.so            libitm.so.1.0.0   libstdc++.so.6.0.35-gdb.py
>>> libgcc_s.so.1          libitm.spec       libsupc++.a
>>> libgomp.a              libstdc++.a       libsupc++.la
>>> [hjl@gnu-zen4-1 lib]$ file libatomic.so.1.2.0
>>> libatomic.so.1.2.0: ELF 32-bit MSB shared object, SPARC32PLUS, V8+
>>> Required, total store ordering, version 1 (SYSV), dynamically linked,
>>> with debug_info, not stripped
>>> [hjl@gnu-zen4-1 lib]$
>>>
>>> Something seems wrong in your setup.
>> I built the sparc64 toolchain using build-many-glibcs.py and vanilla branches:
>>
>> * binutils: origin/binutils-2_46-branch (7db5c37036f2ddbf0db6199df6342f7945575623)
>> * gcc:      origin/releases/gcc-16 (3ddd3407b1d0a0f49a606ea95d5dd190dd6e2d31)
>> * glibc:    origin/release/2.43/master (e9517114acc77c0b8af9da6700107df16882b701)
>>
>> No extra patch applied.
> 
> What OS does your machine run?
> 
> 

It is a default x86_64 Ubuntu 24:

$ uname -s -r -m
Linux 6.8.0-111-generic x86_64