On Dec 6, 2023, Jonathan Wakely <[email protected]> wrote:
>> - void *obj, void *dso_handle)
>> + void *obj, [[maybe_unused]] void
>> *dso_handle)
> The patch is OK with that change.
Thanks, here's what I'm going to install. Regstrapped on
x86_64-linux-gnu, with and without
ac_cv_func___cxa_thread_atexit_impl=no, on a machine that has
__cxa_thread_atexit_impl (but not __cxa_thread_atexit) in libc.
libsupc++: try cxa_thread_atexit_impl at runtime
g++.dg/tls/thread_local-order2.C fails when the toolchain is built for
a platform that lacks __cxa_thread_atexit_impl, even if the program is
built and run using that toolchain on a (later) platform that offers
__cxa_thread_atexit_impl.
This patch adds runtime testing for __cxa_thread_atexit_impl on select
platforms (GNU variants, for starters) that support weak symbols.
for libstdc++-v3/ChangeLog
PR libstdc++/112858
* config/os/gnu-linux/os_defines.h
(_GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL): Define.
* libsupc++/atexit_thread.cc [__GXX_WEAK__ &&
_GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL]
(__cxa_thread_atexit): Add dynamic detection of
__cxa_thread_atexit_impl.
---
libstdc++-v3/config/os/gnu-linux/os_defines.h | 5 +++++
libstdc++-v3/libsupc++/atexit_thread.cc | 23 ++++++++++++++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/config/os/gnu-linux/os_defines.h
b/libstdc++-v3/config/os/gnu-linux/os_defines.h
index 87317031fcd71..a2e4baec069d5 100644
--- a/libstdc++-v3/config/os/gnu-linux/os_defines.h
+++ b/libstdc++-v3/config/os/gnu-linux/os_defines.h
@@ -60,6 +60,11 @@
# define _GLIBCXX_HAVE_FLOAT128_MATH 1
#endif
+// Enable __cxa_thread_atexit to rely on a (presumably libc-provided)
+// __cxa_thread_atexit_impl, if it happens to be defined, even if
+// configure couldn't find it during the build.
+#define _GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL 1
+
#ifdef __linux__
// The following libpthread properties only apply to Linux, not GNU/Hurd.
diff --git a/libstdc++-v3/libsupc++/atexit_thread.cc
b/libstdc++-v3/libsupc++/atexit_thread.cc
index 9346d50f5dafe..28423344a0f34 100644
--- a/libstdc++-v3/libsupc++/atexit_thread.cc
+++ b/libstdc++-v3/libsupc++/atexit_thread.cc
@@ -138,11 +138,32 @@ namespace {
}
}
+#if __GXX_WEAK__ && _GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL
+extern "C"
+int __attribute__ ((__weak__))
+__cxa_thread_atexit_impl (void (_GLIBCXX_CDTOR_CALLABI *func) (void *),
+ void *arg, void *d);
+#endif
+
+// ??? We can't make it an ifunc, can we?
extern "C" int
__cxxabiv1::__cxa_thread_atexit (void (_GLIBCXX_CDTOR_CALLABI *dtor)(void *),
- void *obj, void */*dso_handle*/)
+ void *obj, [[maybe_unused]] void *dso_handle)
_GLIBCXX_NOTHROW
{
+#if __GXX_WEAK__ && _GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL
+ if (__cxa_thread_atexit_impl)
+ // Rely on a (presumably libc-provided) __cxa_thread_atexit_impl,
+ // if it happens to be defined, even if configure couldn't find it
+ // during the build. _GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL
+ // may be defined e.g. in os_defines.h on platforms where some
+ // versions of libc have a __cxa_thread_atexit_impl definition,
+ // but whose earlier versions didn't. This enables programs build
+ // by toolchains compatible with earlier libc versions to still
+ // benefit from a libc-provided __cxa_thread_atexit_impl.
+ return __cxa_thread_atexit_impl (dtor, obj, dso_handle);
+#endif
+
// Do this initialization once.
if (__gthread_active_p ())
{
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive
