libstdc++, Darwin: Handle a linker warning [PR112397].

Darwin's linker warns when we make a direct branch to code that is
in a weak definition (citing that if a different implementation of
the weak function is chosen by the dynamic linker this would be an
error).

As the analysis in the PR shows, this can happen when we have hot/
cold partitioning and there is an error path that is primarily cold
but makes use of epilogue code in the hot section.  In this simple
case, we can easily deduce that the code is in fact safe; however
that is not something we can realistically implement in the linker.

Since the user-replaceable allocators are implemented using weak
definitions, this is a warning that is frequently flagged up in both
the testsuite and end-user code.

The chosen solution here is to suppress the hot/cold partitioning for
these cases (it is unlikely to impact performance much c.f. the
actual allocation).

	PR target/112397

libstdc++-v3/ChangeLog:

	* configure: Regenerate.
	* configure.ac: Detect if we are building for Darwin.
	* libsupc++/Makefile.am: If we are building for Darwin, then
	suppress hot/cold partitioning for the array allocators.
	* libsupc++/Makefile.in: Regenerated.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
(cherry picked from commit 1609fdff16f17ead37666f6d0e801800ee3d04d2)

4 files changed, 50 insertions, 9 deletions

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 8633b8a..316c19a 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -776,6 +776,8 @@ GLIBCXX_HOSTED_TRUE
 glibcxx_compiler_shared_flag
 glibcxx_compiler_pic_flag
 glibcxx_lt_pic_flag
+OS_IS_DARWIN_FALSE
+OS_IS_DARWIN_TRUE
 enable_static
 enable_shared
 lt_host_flags
@@ -12176,7 +12178,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12179 "configure"
+#line 12181 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12282,7 +12284,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12285 "configure"
+#line 12287 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15564,6 +15566,20 @@ esac
 
 
 
+os_is_darwin=no
+case ${host_os} in
+  darwin*) os_is_darwin=yes ;;
+  *) ;;
+esac
+ if test x${os_is_darwin} = xyes; then
+  OS_IS_DARWIN_TRUE=
+  OS_IS_DARWIN_FALSE='#'
+else
+  OS_IS_DARWIN_TRUE='#'
+  OS_IS_DARWIN_FALSE=
+fi
+
+
 if test "$enable_vtable_verify" = yes; then
   predep_objects_CXX="${predep_objects_CXX} ${glibcxx_builddir}/../libgcc/vtv_start.o"
   postdep_objects_CXX="${postdep_objects_CXX} ${glibcxx_builddir}/../libgcc/vtv_end.o"
@@ -15964,7 +15980,7 @@ $as_echo "$glibcxx_cv_atomic_long_long" >&6; }
   # Fake what AC_TRY_COMPILE does.
 
     cat > conftest.$ac_ext << EOF
-#line 15967 "configure"
+#line 15983 "configure"
 int main()
 {
   typedef bool atomic_type;
@@ -15999,7 +16015,7 @@ $as_echo "$glibcxx_cv_atomic_bool" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16002 "configure"
+#line 16018 "configure"
 int main()
 {
   typedef short atomic_type;
@@ -16034,7 +16050,7 @@ $as_echo "$glibcxx_cv_atomic_short" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16037 "configure"
+#line 16053 "configure"
 int main()
 {
   // NB: _Atomic_word not necessarily int.
@@ -16070,7 +16086,7 @@ $as_echo "$glibcxx_cv_atomic_int" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16073 "configure"
+#line 16089 "configure"
 int main()
 {
   typedef long long atomic_type;
@@ -16223,7 +16239,7 @@ $as_echo "mutex" >&6; }
   # unnecessary for this test.
 
     cat > conftest.$ac_ext << EOF
-#line 16226 "configure"
+#line 16242 "configure"
 int main()
 {
   _Decimal32 d1;
@@ -16265,7 +16281,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
   # unnecessary for this test.
 
     cat > conftest.$ac_ext << EOF
-#line 16268 "configure"
+#line 16284 "configure"
 template<typename T1, typename T2>
   struct same
   { typedef T2 type; };
@@ -16299,7 +16315,7 @@ $as_echo "$enable_int128" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16302 "configure"
+#line 16318 "configure"
 template<typename T1, typename T2>
   struct same
   { typedef T2 type; };
@@ -78444,6 +78460,10 @@ if test -z "${MAINTAINER_MODE_TRUE}" && test -z "${MAINTAINER_MODE_FALSE}"; then
   as_fn_error $? "conditional \"MAINTAINER_MODE\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${OS_IS_DARWIN_TRUE}" && test -z "${OS_IS_DARWIN_FALSE}"; then
+  as_fn_error $? "conditional \"OS_IS_DARWIN\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 if test -z "${GLIBCXX_HOSTED_TRUE}" && test -z "${GLIBCXX_HOSTED_FALSE}"; then
   as_fn_error $? "conditional \"GLIBCXX_HOSTED\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 4d16b09..6c823ef 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -98,6 +98,13 @@ ACX_LT_HOST_FLAGS
 AC_SUBST(enable_shared)
 AC_SUBST(enable_static)
 
+os_is_darwin=no
+case ${host_os} in
+  darwin*) os_is_darwin=yes ;;
+  *) ;;
+esac
+AM_CONDITIONAL([OS_IS_DARWIN], [test x${os_is_darwin} = xyes])
+
 if test "$enable_vtable_verify" = yes; then
   predep_objects_CXX="${predep_objects_CXX} ${glibcxx_builddir}/../libgcc/vtv_start.o"
   postdep_objects_CXX="${postdep_objects_CXX} ${glibcxx_builddir}/../libgcc/vtv_end.o"
diff --git a/libstdc++-v3/libsupc++/Makefile.am b/libstdc++-v3/libsupc++/Makefile.am
index 10ac4bb..c857702 100644
--- a/libstdc++-v3/libsupc++/Makefile.am
+++ b/libstdc++-v3/libsupc++/Makefile.am
@@ -132,6 +132,14 @@ atomicity_file = ${glibcxx_srcdir}/$(ATOMICITY_SRCDIR)/atomicity.h
 atomicity.cc: ${atomicity_file}
 	$(LN_S) ${atomicity_file} ./atomicity.cc || true
 
+if OS_IS_DARWIN
+# See PR 112397
+new_opvnt.lo: new_opvnt.cc
+	$(LTCXXCOMPILE) -fno-reorder-blocks-and-partition -I. -c $<
+new_opvnt.o: new_opvnt.cc
+	$(CXXCOMPILE) -fno-reorder-blocks-and-partition -I. -c $<
+endif
+
 # AM_CXXFLAGS needs to be in each subdirectory so that it can be
 # modified in a per-library or per-sub-library way.  Need to manually
 # set this option because CONFIG_CXXFLAGS has to be after
diff --git a/libstdc++-v3/libsupc++/Makefile.in b/libstdc++-v3/libsupc++/Makefile.in
index 5776a56..b5fd8ea 100644
--- a/libstdc++-v3/libsupc++/Makefile.in
+++ b/libstdc++-v3/libsupc++/Makefile.in
@@ -965,6 +965,12 @@ cp-demangle.o: cp-demangle.c
 atomicity.cc: ${atomicity_file}
 	$(LN_S) ${atomicity_file} ./atomicity.cc || true
 
+# See PR 112397
+@OS_IS_DARWIN_TRUE@new_opvnt.lo: new_opvnt.cc
+@OS_IS_DARWIN_TRUE@	$(LTCXXCOMPILE) -fno-reorder-blocks-and-partition -I. -c $<
+@OS_IS_DARWIN_TRUE@new_opvnt.o: new_opvnt.cc
+@OS_IS_DARWIN_TRUE@	$(CXXCOMPILE) -fno-reorder-blocks-and-partition -I. -c $<
+
 install-stdHEADERS: $(std_HEADERS)
 	@$(NORMAL_INSTALL)
 	$(mkinstalldirs) $(DESTDIR)$(stddir)