[PATCH] Link static C++ tests against libatomic.a if needed
H.J. Lu
hjl.tools@gmail.com
Tue May 5 21:20:21 GMT 2026
On Wed, May 6, 2026 at 5:10 AM H.J. Lu <hjl.tools@gmail.com> 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?
Please show the full command-line options passed to ld. Mine
sparc64-glibc-linux-gnu-gcc -m32 -mlong-double-128 -mcpu=v9 -o
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/support/links-dso-program
-nostdlib -nostartfiles -Wl,-z,relro
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/csu/crt1.o
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/csu/crti.o
`sparc64-glibc-linux-gnu-gcc -m32 -mlong-double-128 -mcpu=v9
--print-file-name=crtbegin.o`
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/support/links-dso-program.o
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/support/libsupport_nonshared.a
-lstdc++ -lgcc -lgcc_s -Wl,-dynamic-linker=/lib/ld-linux.so.2
-Wl,-rpath-link=/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/math:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/elf:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/dlfcn:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/nss:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/nis:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/rt:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/resolv:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/mathvec:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/support:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/misc:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/debug:/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/nptl:/export/build/gnu/tools-build/glibc-many/install/compilers/sparc64-linux-gnu/lib/gcc/sparc64-glibc-linux-gnu/16.1.1/../../../../sparc64-glibc-linux-gnu/lib/../lib/
-lgcc -Wl,--as-needed -lgcc_s -Wl,--no-as-needed
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/libc.so.6
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/libc_nonshared.a
-Wl,--as-needed
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/elf/ld.so
-Wl,--no-as-needed -lgcc -Wl,--as-needed -lgcc_s -Wl,--no-as-needed
`sparc64-glibc-linux-gnu-gcc -m32 -mlong-double-128 -mcpu=v9
--print-file-name=crtend.o`
/export/build/gnu/tools-build/glibc-many/build/glibcs/sparcv9-linux-gnu/glibc/csu/crtn.o
works.
--
H.J.
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