Re: [PATCH] Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc

[Thomas Schwinge]

Hi!

On Wed, 11 Apr 2018 20:55:49 +0200, 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:
> > > 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

Re: [PATCH] Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc

[Jeff Law]

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  
> 
>   * 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

Re: [PATCH] Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc

[Matthias Klose]

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.

Re: [PATCH] Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc

[Jakub Jelinek]

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  

* 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.ac2018-04-11 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.jj2018-04-10 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

Re: [PATCH] Use --push-state --as-needed and --pop-state instead of --as-needed and --no-as-needed for libgcc

[Matthias Klose]

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