[gcc r12-10376] libstdc++, Darwin: Handle a linker warning [PR112397].

[gcc r12-10376] libstdc++, Darwin: Handle a linker warning [PR112397].

[Iain D Sandoe]

https://gcc.gnu.org/g:77f17e405a0669db9a6c8af69bde6eb1170f48bd

commit r12-10376-g77f17e405a0669db9a6c8af69bde6eb1170f48bd
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Thu Feb 8 17:54:31 2024 +0000

    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)

Diff:
---
 libstdc++-v3/configure             | 36 ++++++++++++++++++++++++++++--------
 libstdc++-v3/configure.ac          |  7 +++++++
 libstdc++-v3/libsupc++/Makefile.am |  8 ++++++++
 libstdc++-v3/libsupc++/Makefile.in |  6 ++++++
 4 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index bc92ce1303c..ccc23f1b352 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -786,6 +786,8 @@ 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
@@ -12191,7 +12193,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12194 "configure"
+#line 12196 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12297,7 +12299,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 12300 "configure"
+#line 12302 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -15579,6 +15581,20 @@ 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"
@@ -15981,7 +15997,7 @@ $as_echo "$glibcxx_cv_atomic_long_long" >&6; }
   # Fake what AC_TRY_COMPILE does.
 
     cat > conftest.$ac_ext << EOF
-#line 15984 "configure"
+#line 16000 "configure"
 int main()
 {
   typedef bool atomic_type;
@@ -16016,7 +16032,7 @@ $as_echo "$glibcxx_cv_atomic_bool" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16019 "configure"
+#line 16035 "configure"
 int main()
 {
   typedef short atomic_type;
@@ -16051,7 +16067,7 @@ $as_echo "$glibcxx_cv_atomic_short" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16054 "configure"
+#line 16070 "configure"
 int main()
 {
   // NB: _Atomic_word not necessarily int.
@@ -16087,7 +16103,7 @@ $as_echo "$glibcxx_cv_atomic_int" >&6; }
     rm -f conftest*
 
     cat > conftest.$ac_ext << EOF
-#line 16090 "configure"
+#line 16106 "configure"
 int main()
 {
   typedef long long atomic_type;
@@ -16243,7 +16259,7 @@ $as_echo "mutex" >&6; }
   # unnecessary for this test.
 
     cat > conftest.$ac_ext << EOF
-#line 16246 "configure"
+#line 16262 "configure"
 int main()
 {
   _Decimal32 d1;
@@ -16285,7 +16301,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
   # unnecessary for this test.
 
   cat > conftest.$ac_ext << EOF
-#line 16288 "configure"
+#line 16304 "configure"
 template<typename T1, typename T2>
   struct same
   { typedef T2 type; };
@@ -79293,6 +79309,10 @@ if test -z "${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 e59bcdb2944..dc0c61973d1 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -100,6 +100,13 @@ 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 65b5c1a87fd..4e63ad04a58 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 a4402009b85..22c9680f979 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)