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>

4 files changed, 47 insertions, 8 deletions

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index f4bc048..21abaeb 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -789,6 +789,8 @@ GLIBCXX_HOSTED_TRUE
 glibcxx_compiler_shared_flag
 glibcxx_compiler_pic_flag
 glibcxx_lt_pic_flag
+OS_IS_DARWIN_FALSE
+OS_IS_DARWIN_TRUE
 ENABLE_DARWIN_AT_RPATH_FALSE
 ENABLE_DARWIN_AT_RPATH_TRUE
 enable_static
@@ -12278,7 +12280,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12281 "configure"
+#line 12283 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12384,7 +12386,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12387 "configure"
+#line 12389 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15744,6 +15746,19 @@ else
   ENABLE_DARWIN_AT_RPATH_FALSE=
 fi
 
+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"
@@ -16167,7 +16182,7 @@ $as_echo "$glibcxx_cv_atomic_long_long" >&6; }
   # Fake what AC_TRY_COMPILE does.
 
     cat > conftest.$ac_ext << EOF
-#line 16170 "configure"
+#line 16185 "configure"
 int main()
 {
   typedef bool atomic_type;
@@ -16202,7 +16217,7 @@ $as_echo "$glibcxx_cv_atomic_bool" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16205 "configure"
+#line 16220 "configure"
 int main()
 {
   typedef short atomic_type;
@@ -16237,7 +16252,7 @@ $as_echo "$glibcxx_cv_atomic_short" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16240 "configure"
+#line 16255 "configure"
 int main()
 {
   // NB: _Atomic_word not necessarily int.
@@ -16273,7 +16288,7 @@ $as_echo "$glibcxx_cv_atomic_int" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16276 "configure"
+#line 16291 "configure"
 int main()
 {
   typedef long long atomic_type;
@@ -16429,7 +16444,7 @@ $as_echo "mutex" >&6; }
   # unnecessary for this test.
 
     cat > conftest.$ac_ext << EOF
-#line 16432 "configure"
+#line 16447 "configure"
 int main()
 {
   _Decimal32 d1;
@@ -16471,7 +16486,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
   # unnecessary for this test.
 
   cat > conftest.$ac_ext << EOF
-#line 16474 "configure"
+#line 16489 "configure"
 template<typename T1, typename T2>
   struct same
   { typedef T2 type; };
@@ -55833,6 +55848,10 @@ if test -z "${ENABLE_DARWIN_AT_RPATH_TRUE}" && test -z "${ENABLE_DARWIN_AT_RPATH
   as_fn_error $? "conditional \"ENABLE_DARWIN_AT_RPATH\" was never defined.
 Usually this means the macro was only invoked conditionally." "$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 c68cac4..37396bd 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -109,6 +109,12 @@ ACX_LT_HOST_FLAGS
 AC_SUBST(enable_shared)
 AC_SUBST(enable_static)
 AM_CONDITIONAL([ENABLE_DARWIN_AT_RPATH], [test x$enable_darwin_at_rpath = xyes])
+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"
diff --git a/libstdc++-v3/libsupc++/Makefile.am b/libstdc++-v3/libsupc++/Makefile.am
index d0e1618..e151ce7 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 2e755ab..732ab89 100644
--- a/libstdc++-v3/libsupc++/Makefile.in
+++ b/libstdc++-v3/libsupc++/Makefile.in
@@ -973,6 +973,12 @@ 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)