Jakub Jelinek 8a99fdb704 Use -latomic_asneeded or -lgcc_s_asneeded to workaround libtool issues [PR123396]
On Mon, Jan 12, 2026 at 12:13:35PM +0100, Florian Weimer wrote:
> One way to work around the libtool problem would be to stick the
> as-needed into an existing .so linker script, or create a new one under
> a different name (say libatomic_optional.so) that has AS_NEEDED in it,
> and link with -latomic_optional.  Then libtool would not have to be
> taught about --push-state/--pop-state etc.

That seems to work.

So far bootstrapped (c,c++,fortran,lto only) and make install tested
on x86_64-linux, tested on a small program without need to libatomic and
struct S { char a[25]; };
_Atomic struct S s;

int main () { struct S t = s; s = t; }
which does at -O0.
Before this patch I got
for i in `find x86_64-pc-linux-gnu/ -name lib\*.so.\*.\*`; do ldd -u $i 2>&1 | grep -q libatomic.so.1 && echo $i; done
x86_64-pc-linux-gnu/libsanitizer/ubsan/.libs/libubsan.so.1.0.0
x86_64-pc-linux-gnu/libsanitizer/asan/.libs/libasan.so.8.0.0
x86_64-pc-linux-gnu/libsanitizer/hwasan/.libs/libhwasan.so.0.0.0
x86_64-pc-linux-gnu/libsanitizer/lsan/.libs/liblsan.so.0.0.0
x86_64-pc-linux-gnu/libsanitizer/tsan/.libs/libtsan.so.2.0.0
x86_64-pc-linux-gnu/32/libsanitizer/ubsan/.libs/libubsan.so.1.0.0
x86_64-pc-linux-gnu/32/libsanitizer/asan/.libs/libasan.so.8.0.0
x86_64-pc-linux-gnu/32/libstdc++-v3/src/.libs/libstdc++.so.6.0.35
x86_64-pc-linux-gnu/libgcobol/.libs/libgcobol.so.2.0.0
x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6.0.35
With this patch it prints nothing.

2026-01-13  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/123396
gcc/
	* configure.ac (gcc_cv_ld_use_as_needed_ldscript): New test.
	(USE_LD_AS_NEEDED_LDSCRIPT): New AC_DEFINE.
	* gcc.cc (LINK_LIBATOMIC_SPEC): Use "-latomic_asneeded" instead
	of LD_AS_NEEDED_OPTION " -latomic " LD_NO_AS_NEEDED_OPTION
	if USE_LD_AS_NEEDED_LDSCRIPT is defined.
	(init_gcc_specs): Use "-lgcc_s_asneeded" instead of
	LD_AS_NEEDED_OPTION " -lgcc_s " LD_NO_AS_NEEDED_OPTION
	if USE_LD_AS_NEEDED_LDSCRIPT is defined.
	* config.in: Regenerate.
	* configure: Regenerate.
libatomic/
	* acinclude.m4 (LIBAT_BUILD_ASNEEDED_SOLINK): New AM_CONDITIONAL.
	* libatomic_asneeded.so: New file.
	* libatomic_asneeded.a: New file.
	* Makefile.am (toolexeclib_DATA): Set if LIBAT_BUILD_ASNEEDED_SOLINK.
	(all-local): Install those files into gcc subdir.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
libgcc/
	* config/t-slibgcc (SHLIB_ASNEEDED_SOLINK,
	SHLIB_MAKE_ASNEEDED_SOLINK, SHLIB_INSTALL_ASNEEDED_SOLINK): New
	vars.
	(SHLIB_LINK): Include $(SHLIB_MAKE_ASNEEDED_SOLINK).
	(SHLIB_INSTALL): Include $(SHLIB_INSTALL_ASNEEDED_SOLINK).
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