libstdc++: Prevent std::stacktrace from using atomics on arm-eabi [PR120567]

The conftest.cc in GLIBCXX_ENABLE_BACKTRACE checks if calls to
__atomic_load and __atomic_store result in libatomic calls. For arm-eabi
those expand to normal loads with a call to __sync_synchronize to ensure
correct ordering. That means the generated assembly does not match the
grep pattern "__atomic_" and so configure incorrectly assumes we can use
atomics in libbacktrace.

The fix is to grep for "__atomic_|__sync_" instead of just "__atomic_".

As explained in the bug comments, the similar grep for "__atomic_" in
the GLIBCXX_ENABLE_ATOMIC_BUILTINS macro doesn't need the same change.
That conftest.cc program does emit a call to a libatomic function that
matches the grep pattern "__atomic_" so the test gives the right answer
for arm-eabi.

libstdc++-v3/ChangeLog:

	PR libstdc++/120567
	* acinclude.m4 (GLIBCXX_ENABLE_BACKTRACE): Include "__sync_" in
	grep command to check for extern calls to libatomic.
	* configure: Regenerate.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 38030e432d81b76e640b684575f9c7f02e416797..8dc9e17b214cd30087673c6f4c0707cab3adecc3 100644 (file)
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -5318,7 +5318,7 @@ EOF
 
     AC_MSG_CHECKING([for atomic builtins for libbacktrace])
     if AC_TRY_EVAL(ac_compile); then
-      if grep __atomic_ conftest.s >/dev/null 2>&1 ; then
+      if grep -E '__atomic_|__sync_' conftest.s >/dev/null 2>&1 ; then
        glibcxx_cv_libbacktrace_atomics=no
       else
        glibcxx_cv_libbacktrace_atomics=yes

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 4f144382e1b1acd400b5200db5428fa35dc02cb6..6713e4504b1cd5ac2c7eddea758f8a51ab3d946e 100755 (executable)
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -54172,7 +54172,7 @@ $as_echo_n "checking for atomic builtins for libbacktrace... " >&6; }
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-      if grep __atomic_ conftest.s >/dev/null 2>&1 ; then
+      if grep -E '__atomic_|__sync_' conftest.s >/dev/null 2>&1 ; then
        glibcxx_cv_libbacktrace_atomics=no
       else
        glibcxx_cv_libbacktrace_atomics=yes