| Message ID | 20240218161514.4207-1-iain@sandoe.co.uk |
|---|---|
| State | New |
| Headers | show |
| Series | libstdc++, Darwin: Handle a linker warning [PR112397]. | expand |
On Sun, 18 Feb 2024, 16:15 Iain Sandoe, <iains.gcc@gmail.com> wrote: > Tested on i686-darwin9, x86_64-darwin14,17,19,21,23, x86_64-linux, > aarch64-linux-gnu, > > OK for trunk? > eventual back-ports? > Yup, ok for all. thanks > Iain > > --- 8< --- > > 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> > --- > libstdc++-v3/configure | 35 +++++++++++++++++++++++------- > libstdc++-v3/configure.ac | 6 +++++ > libstdc++-v3/libsupc++/Makefile.am | 8 +++++++ > libstdc++-v3/libsupc++/Makefile.in | 6 +++++ > 4 files changed, 47 insertions(+), 8 deletions(-) > > diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac > index c68cac4f345..37396bd6ebb 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 d0e1618507e..e151ce7a1fe 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 $< > +endif > + > # AM_CXXFLAGS needs to be in each subdirectory so that it can be > # modified in a per-library or per-sub-library way. Need to manually > # set this option because CONFIG_CXXFLAGS has to be after > -- > 2.39.2 (Apple Git-143) > >
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac index c68cac4f345..37396bd6ebb 100644 --- a/libstdc++-v3/configure.ac +++ b/libstdc++-v3/configure.ac @@ -109,6 +109,12 @@ ACX_LT_HOST_FLAGS AC_SUBST(enable_shared) AC_SUBST(enable_static) AM_CONDITIONAL([ENABLE_DARWIN_AT_RPATH], [test x$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 d0e1618507e..e151ce7a1fe 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
Tested on i686-darwin9, x86_64-darwin14,17,19,21,23, x86_64-linux, aarch64-linux-gnu, OK for trunk? eventual back-ports? thanks Iain --- 8< --- 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> --- libstdc++-v3/configure | 35 +++++++++++++++++++++++------- libstdc++-v3/configure.ac | 6 +++++ libstdc++-v3/libsupc++/Makefile.am | 8 +++++++ libstdc++-v3/libsupc++/Makefile.in | 6 +++++ 4 files changed, 47 insertions(+), 8 deletions(-)