[bug#42555] [PATCH core-updates] build-system/gnu: strip with --strip-unneeded

[bug#42555] [PATCH core-updates] build-system/gnu: strip with --strip-unneeded

[Jakub Kądziołka]

Apart from debug information, one can also strip some symbols. This can
be a significant difference, qtbase:out consists of about 5 MB of those
symbols. As per [1], --strip-debug is included in --strip-unneeded, and
the debug files created also contain a copy of the information removed
by --strip-unneeded.

Linux From Scratch suggests that this option shouldn't be used on static
libraries [2], however other sources [3] indicate otherwise. Building a
toolchain with this patch succeeds, and the result works fine for
'gcc -static hello-world.c'.

[1]: https://stackoverflow.com/a/52555093
[2]: http://www.linuxfromscratch.org/lfs/view/9.1/chapter05/stripping.html
[3]: https://www.technovelty.org/linux/stripping-shared-libraries.html

* guix/build/gnu-build-system.scm (strip): Use --strip-unneeded.
---
 guix/build/gnu-build-system.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/guix/build/gnu-build-system.scm b/guix/build/gnu-build-system.scm
index 2e7dff2034..d3347c9518 100644
--- a/guix/build/gnu-build-system.scm
+++ b/guix/build/gnu-build-system.scm
@@ -425,7 +425,7 @@ makefiles."
                 (objcopy-command (if target
                                      (string-append target "-objcopy")
                                      "objcopy"))
-                (strip-flags '("--strip-debug"
+                (strip-flags '("--strip-unneeded"
                                "--enable-deterministic-archives"))
                 (strip-directories '("lib" "lib64" "libexec"
                                      "bin" "sbin"))
-- 
2.27.0

[bug#42555] [PATCH v2 core-updates] build-system/gnu: strip with --strip-unneeded

[Jakub Kądziołka]

Apart from debug information, one can also strip some symbols. This can
be a significant difference, the closure of gcc-toolchain@7 got reduced
by 15 MB in my tests.

As per [1], --strip-debug is included in --strip-unneeded, and
the debug files created also contain a copy of the information removed
by --strip-unneeded.

Linux From Scratch suggests that this option shouldn't be used on static
libraries [2], however other sources [3] indicate otherwise. Building a
toolchain with this patch succeeds, and the result works fine for
'gcc -static hello-world.c'.

[1]: https://stackoverflow.com/a/52555093
[2]: http://www.linuxfromscratch.org/lfs/view/9.1/chapter05/stripping.html
[3]: https://www.technovelty.org/linux/stripping-shared-libraries.html

* guix/build/gnu-build-system.scm (strip): Use --strip-unneeded.
* guix/build-system/gnu.scm (static-package, gnu-build, gnu-cross-build): Likewise.
---

I have realized that my previous patch was a no-op due to default values
for arguments being scattered across files. I ran my builds again and
now I can observe results in the earlier stages of the toolchain,
accessible to a testing core-updates build.

 guix/build-system/gnu.scm       | 6 +++---
 guix/build/gnu-build-system.scm | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/guix/build-system/gnu.scm b/guix/build-system/gnu.scm
index 6b481ad45c..2c23197e77 100644
--- a/guix/build-system/gnu.scm
+++ b/guix/build-system/gnu.scm
@@ -215,7 +215,7 @@ use `--strip-all' as the arguments to `strip'."
     (arguments
      (let ((a (default-keyword-arguments (package-arguments p)
                 '(#:configure-flags '()
-                  #:strip-flags '("--strip-debug")))))
+                  #:strip-flags '("--strip-unneeded")))))
        (substitute-keyword-arguments a
          ((#:configure-flags flags)
           `(cons* "--disable-shared" "LDFLAGS=-static" ,flags))
@@ -337,7 +337,7 @@ standard packages used as implicit inputs of the GNU build system."
                     (parallel-tests? #t)
                     (patch-shebangs? #t)
                     (strip-binaries? #t)
-                    (strip-flags ''("--strip-debug"
+                    (strip-flags ''("--strip-unneeded"
                                     "--enable-deterministic-archives"))
                     (strip-directories ''("lib" "lib64" "libexec"
                                           "bin" "sbin"))
@@ -492,7 +492,7 @@ is one of `host' or `target'."
                           (parallel-build? #t) (parallel-tests? #t)
                           (patch-shebangs? #t)
                           (strip-binaries? #t)
-                          (strip-flags ''("--strip-debug"
+                          (strip-flags ''("--strip-unneeded"
                                           "--enable-deterministic-archives"))
                           (strip-directories ''("lib" "lib64" "libexec"
                                                 "bin" "sbin"))
diff --git a/guix/build/gnu-build-system.scm b/guix/build/gnu-build-system.scm
index 2e7dff2034..d3347c9518 100644
--- a/guix/build/gnu-build-system.scm
+++ b/guix/build/gnu-build-system.scm
@@ -425,7 +425,7 @@ makefiles."
                 (objcopy-command (if target
                                      (string-append target "-objcopy")
                                      "objcopy"))
-                (strip-flags '("--strip-debug"
+                (strip-flags '("--strip-unneeded"
                                "--enable-deterministic-archives"))
                 (strip-directories '("lib" "lib64" "libexec"
                                      "bin" "sbin"))
-- 
2.28.0

[bug#42555] [PATCH v2 core-updates] build-system/gnu: strip with --strip-unneeded

[Ludovic Courtès]

Hi Jakub,

Jakub Kądziołka <kuba@kadziolka.net> skribis:

> Apart from debug information, one can also strip some symbols. This can
> be a significant difference, the closure of gcc-toolchain@7 got reduced
> by 15 MB in my tests.

Nice!  Now’s a good time to get that patch in on ‘core-updates’.

> As per [1], --strip-debug is included in --strip-unneeded, and
> the debug files created also contain a copy of the information removed
> by --strip-unneeded.

Hmm the Binutils manual suggests otherwise (info "(binutils) objcopy"):

--8<---------------cut here---------------start------------->8---
'-g'
'--strip-debug'
     Do not copy debugging symbols or sections from the source file.

'--strip-unneeded'
     Strip all symbols that are not needed for relocation processing.
--8<---------------cut here---------------end--------------->8---

… but objcopy.c reads this:

--8<---------------cut here---------------start------------->8---
      else if ((flags & BSF_DEBUGGING) != 0)	/* Debugging symbol.  */
	keep = (strip_symbols != STRIP_DEBUG
		&& strip_symbols != STRIP_UNNEEDED
		&& ! convert_debugging);
--8<---------------cut here---------------end--------------->8---

… confirming that ‘--strip-unneeded’ includes ‘--strip-debug’.

I submitted a patch for the Binutils manual.

> Linux From Scratch suggests that this option shouldn't be used on static
> libraries [2], however other sources [3] indicate otherwise. Building a
> toolchain with this patch succeeds, and the result works fine for
> 'gcc -static hello-world.c'.

OK.

> [1]: https://stackoverflow.com/a/52555093

Perhaps we can omit this one.  In general, I think it’s safer to refer
to “primary sources” as Wikipedians would say.

> [2]: http://www.linuxfromscratch.org/lfs/view/9.1/chapter05/stripping.html
> [3]: https://www.technovelty.org/linux/stripping-shared-libraries.html
>
> * guix/build/gnu-build-system.scm (strip): Use --strip-unneeded.
> * guix/build-system/gnu.scm (static-package, gnu-build, gnu-cross-build): Likewise.

LGTM!

For the record, I tried ‘--strip-all’ before, but that was problematic
for some reason:

  https://lists.gnu.org/archive/html/guix-devel/2018-03/msg00135.html

Thanks,
Ludo’.

bug#42555: [PATCH v2 core-updates] build-system/gnu: strip with --strip-unneeded

[Jakub Kądziołka]

On Sat Sep 19, 2020 at 4:49 PM CEST, Ludovic Courtès wrote:
> Hi Jakub,
>
> Jakub Kądziołka <kuba@kadziolka.net> skribis:
>
> > Apart from debug information, one can also strip some symbols. This can
> > be a significant difference, the closure of gcc-toolchain@7 got reduced
> > by 15 MB in my tests.
>
> Nice! Now’s a good time to get that patch in on ‘core-updates’.

Thanks. Patch pushed (with a small hiccup...)

> > [1]: https://stackoverflow.com/a/52555093
>
> Perhaps we can omit this one. In general, I think it’s safer to refer
> to “primary sources” as Wikipedians would say.

The problem with "primary sources" is that the docs on this are quite
sparse. I think this link is much more comprehensive.

> > [2]: http://www.linuxfromscratch.org/lfs/view/9.1/chapter05/stripping.html
> > [3]: https://www.technovelty.org/linux/stripping-shared-libraries.html
> >
> > * guix/build/gnu-build-system.scm (strip): Use --strip-unneeded.
> > * guix/build-system/gnu.scm (static-package, gnu-build, gnu-cross-build): Likewise.
>
> LGTM!
>
> For the record, I tried ‘--strip-all’ before, but that was
> problematic
> for some reason:
>
> https://lists.gnu.org/archive/html/guix-devel/2018-03/msg00135.html

The docs for --strip-all say "Do not copy relocation and symbol
information", so I would expect some relocation and/or linking use case
to get broken...

Regards,
Jakub Kądziołka