| Message ID | 20180411103108.GP8577@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc | expand |
On 11.04.2018 12:31, Jakub Jelinek wrote: > Hi! > > As discussed, using --as-needed and --no-as-needed is dangerous, because > it results in --no-as-needed even for libraries after -lgcc_s, even when the > default is --as-needed or --as-needed has been specified earlier on the > command line. > > If the linker supports --push-state/--pop-state, we should IMHO use it. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1? > > Or is this something we want in GCC8 too? this is problematic for binutils versions with --push-state/--pop-state support in the BFD linker but not in gold, and then using -fuse-ld=gold. So maybe the version check for the BFD linker should only succeed for the first binutils version which also has -push-state/--pop-state support in gold. The BFD linker is only able to save exactly one state, and nested --push-state calls override the state (binutils PR23043). Otoh, there is not much linked after libgcc, so maybe this is not an issue. Matthias
On Wed, Apr 11, 2018 at 06:07:17PM +0200, Matthias Klose wrote: > On 11.04.2018 12:31, Jakub Jelinek wrote: > > Hi! > > > > As discussed, using --as-needed and --no-as-needed is dangerous, because > > it results in --no-as-needed even for libraries after -lgcc_s, even when the > > default is --as-needed or --as-needed has been specified earlier on the > > command line. > > > > If the linker supports --push-state/--pop-state, we should IMHO use it. > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1? > > > > Or is this something we want in GCC8 too? > > this is problematic for binutils versions with --push-state/--pop-state support > in the BFD linker but not in gold, and then using -fuse-ld=gold. So maybe the > version check for the BFD linker should only succeed for the first binutils > version which also has -push-state/--pop-state support in gold. Does anybody use -fuse-ld=gold? > The BFD linker is only able to save exactly one state, and nested --push-state > calls override the state (binutils PR23043). Otoh, there is not much linked > after libgcc, so maybe this is not an issue. In any case, here is updated patch that will use it only for 2.28+ which should have both ld.bfd and ld.gold --push-state support. Bootstrapped/regtested on x86_64-linux and i686-linux. 2018-04-11 Jakub Jelinek <jakub@redhat.com> * configure.ac (LD_AS_NEEDED_OPTION, LD_NO_AS_NEEDED_OPTION): Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed if ld supports it. * configure: Regenerated. --- gcc/configure.ac.jj 2018-04-10 14:35:49.764788806 +0200 +++ gcc/configure.ac 2018-04-11 18:26:16.745563830 +0200 @@ -5517,11 +5517,25 @@ if test $in_tree_ld = yes ; then if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 \ && test $in_tree_ld_is_elf = yes; then gcc_cv_ld_as_needed=yes + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 28; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi elif test x$gcc_cv_ld != x; then # Check if linker supports --as-needed and --no-as-needed options if $gcc_cv_ld --help 2>&1 | grep as-needed > /dev/null; then gcc_cv_ld_as_needed=yes + if $gcc_cv_ld --help 2>&1 | grep push-state > /dev/null \ + && $gcc_cv_ld --help 2>&1 | grep pop-state > /dev/null \ + && echo "$ld_ver" | grep GNU > /dev/null \ + && test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 28; then + # Use these options only when both ld.bfd and ld.gold support + # --push-state/--pop-state, which unfortunately wasn't added + # at the same time. + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi case "$target:$gnu_ld" in *-*-solaris2*:no) --- gcc/configure.jj 2018-04-10 14:35:49.875788826 +0200 +++ gcc/configure 2018-04-11 18:26:28.162568402 +0200 @@ -28733,11 +28733,25 @@ if test $in_tree_ld = yes ; then if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 \ && test $in_tree_ld_is_elf = yes; then gcc_cv_ld_as_needed=yes + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 28; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi elif test x$gcc_cv_ld != x; then # Check if linker supports --as-needed and --no-as-needed options if $gcc_cv_ld --help 2>&1 | grep as-needed > /dev/null; then gcc_cv_ld_as_needed=yes + if $gcc_cv_ld --help 2>&1 | grep push-state > /dev/null \ + && $gcc_cv_ld --help 2>&1 | grep pop-state > /dev/null \ + && echo "$ld_ver" | grep GNU > /dev/null \ + && test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 28; then + # Use these options only when both ld.bfd and ld.gold support + # --push-state/--pop-state, which unfortunately wasn't added + # at the same time. + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi case "$target:$gnu_ld" in *-*-solaris2*:no) Jakub
On 11.04.2018 20:55, Jakub Jelinek wrote: > On Wed, Apr 11, 2018 at 06:07:17PM +0200, Matthias Klose wrote: >> On 11.04.2018 12:31, Jakub Jelinek wrote: >>> Hi! >>> >>> As discussed, using --as-needed and --no-as-needed is dangerous, because >>> it results in --no-as-needed even for libraries after -lgcc_s, even when the >>> default is --as-needed or --as-needed has been specified earlier on the >>> command line. >>> >>> If the linker supports --push-state/--pop-state, we should IMHO use it. >>> >>> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1? >>> >>> Or is this something we want in GCC8 too? >> >> this is problematic for binutils versions with --push-state/--pop-state support >> in the BFD linker but not in gold, and then using -fuse-ld=gold. So maybe the >> version check for the BFD linker should only succeed for the first binutils >> version which also has -push-state/--pop-state support in gold. > > Does anybody use -fuse-ld=gold? grep the build log of your favorite distro, unless these are not beautified and not showing any command line options. For Debian/Ubuntu it's haskell using gold by default, and some upstreams like systemd turns it on by default, assuming it has the same quality on any architecture.
On 04/11/2018 04:31 AM, Jakub Jelinek wrote: > Hi! > > As discussed, using --as-needed and --no-as-needed is dangerous, because > it results in --no-as-needed even for libraries after -lgcc_s, even when the > default is --as-needed or --as-needed has been specified earlier on the > command line. > > If the linker supports --push-state/--pop-state, we should IMHO use it. > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1? > > Or is this something we want in GCC8 too? > > 2018-04-11 Jakub Jelinek <jakub@redhat.com> > > * configure.ac (LD_AS_NEEDED_OPTION, LD_NO_AS_NEEDED_OPTION): Use > --push-state --as-needed and --pop-state instead of --as-needed and > --no-as-needed if ld supports it. > * configure: Regenerated. OK for the trunk. jeff
Hi! On Wed, 11 Apr 2018 20:55:49 +0200, Jakub Jelinek <jakub@redhat.com> wrote: > On Wed, Apr 11, 2018 at 06:07:17PM +0200, Matthias Klose wrote: > > On 11.04.2018 12:31, Jakub Jelinek wrote: > > > As discussed, using --as-needed and --no-as-needed is dangerous, because > > > it results in --no-as-needed even for libraries after -lgcc_s, even when the > > > default is --as-needed or --as-needed has been specified earlier on the > > > command line. > > > > > > If the linker supports --push-state/--pop-state, we should IMHO use it. > > > > > > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for stage1? > > this is problematic for binutils versions with --push-state/--pop-state support > > in the BFD linker but not in gold, and then using -fuse-ld=gold. So maybe the > > version check for the BFD linker should only succeed for the first binutils > > version which also has -push-state/--pop-state support in gold. > > Does anybody use -fuse-ld=gold? Probably the question is not whether anybody's using that or not, but rather whether it's supported or not, and last time I looked, it was documented in GCC's manual. ;-) > > The BFD linker is only able to save exactly one state, and nested --push-state > > calls override the state (binutils PR23043). Otoh, there is not much linked > > after libgcc, so maybe this is not an issue. > > In any case, here is updated patch that will use it only for 2.28+ which > should have both ld.bfd and ld.gold --push-state support. > --- gcc/configure.ac.jj 2018-04-10 14:35:49.764788806 +0200 > +++ gcc/configure.ac 2018-04-11 18:26:16.745563830 +0200 > @@ -5517,11 +5517,25 @@ if test $in_tree_ld = yes ; then > if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 \ > && test $in_tree_ld_is_elf = yes; then > gcc_cv_ld_as_needed=yes > + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 28; then > + gcc_cv_ld_as_needed_option='--push-state --as-needed' > + gcc_cv_ld_no_as_needed_option='--pop-state' > + fi > fi > elif test x$gcc_cv_ld != x; then > # Check if linker supports --as-needed and --no-as-needed options > if $gcc_cv_ld --help 2>&1 | grep as-needed > /dev/null; then > gcc_cv_ld_as_needed=yes > + if $gcc_cv_ld --help 2>&1 | grep push-state > /dev/null \ > + && $gcc_cv_ld --help 2>&1 | grep pop-state > /dev/null \ > + && echo "$ld_ver" | grep GNU > /dev/null \ > + && test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 28; then > + # Use these options only when both ld.bfd and ld.gold support > + # --push-state/--pop-state, which unfortunately wasn't added > + # at the same time. > + gcc_cv_ld_as_needed_option='--push-state --as-needed' > + gcc_cv_ld_no_as_needed_option='--pop-state' > + fi Is binutils/ld going to stay at major version 2 forever, or should these checks also include '-o "$gcc_cv_gld_major_version" -gt 2', like done a few lines above, for example? (I have not checked now whether that might be a problem for other existing "feature" checks, too.) Grüße Thomas
--- gcc/configure.ac.jj 2018-03-21 21:18:32.470351282 +0100 +++ gcc/configure.ac 2018-04-10 13:31:25.448060053 +0200 @@ -5517,11 +5517,21 @@ if test $in_tree_ld = yes ; then if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 \ && test $in_tree_ld_is_elf = yes; then gcc_cv_ld_as_needed=yes + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 28; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi elif test x$gcc_cv_ld != x; then # Check if linker supports --as-needed and --no-as-needed options if $gcc_cv_ld --help 2>&1 | grep as-needed > /dev/null; then gcc_cv_ld_as_needed=yes + if $gcc_cv_ld --help 2>&1 | grep push-state > /dev/null; then + if $gcc_cv_ld --help 2>&1 | grep pop-state > /dev/null; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi + fi fi case "$target:$gnu_ld" in *-*-solaris2*:no) --- gcc/configure.jj 2018-03-21 21:18:30.187351579 +0100 +++ gcc/configure 2018-04-10 13:47:57.652298798 +0200 @@ -28733,11 +28733,21 @@ if test $in_tree_ld = yes ; then if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 \ && test $in_tree_ld_is_elf = yes; then gcc_cv_ld_as_needed=yes + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 28; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi fi elif test x$gcc_cv_ld != x; then # Check if linker supports --as-needed and --no-as-needed options if $gcc_cv_ld --help 2>&1 | grep as-needed > /dev/null; then gcc_cv_ld_as_needed=yes + if $gcc_cv_ld --help 2>&1 | grep push-state > /dev/null; then + if $gcc_cv_ld --help 2>&1 | grep pop-state > /dev/null; then + gcc_cv_ld_as_needed_option='--push-state --as-needed' + gcc_cv_ld_no_as_needed_option='--pop-state' + fi + fi fi case "$target:$gnu_ld" in *-*-solaris2*:no)