[PATCH 1/4] Makeconfig: Add libgcc directory to rtld-prefix search path

[Adhemerval Zanella Netto]

On 22/01/25 13:12, dilfridge@gentoo.org wrote:
> From: Andreas K. Hüttel <dilfridge@gentoo.org>
> 
> Signed-off-by: Andreas K. Hüttel <dilfridge@gentoo.org>
> ---
>  Makeconfig | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/Makeconfig b/Makeconfig
> index d0108d2caa..6b4ebd1320 100644
> --- a/Makeconfig
> +++ b/Makeconfig
> @@ -692,6 +692,11 @@ link-libc-static-tests = -Wl,--start-group $(common-objpfx)libc.a $(static-gnuli
>  # some cases and it is preferable to link with libgcc_eh or libgcc_s
>  # so that the testing is as similar as possible to how programs will
>  # be built with the installed glibc.
> +# This leads to moderate difficulties, also since distributions may
> +# install libgcc_s.so in directories only found via ld.so.conf, e.g.
> +# to be able to switch between gcc versions. We need to add the
> +# corresponding directory to the library search path to make sure
> +# our test programs can find it.
>  #
>  # Some architectures have architecture-specific systems for exception
>  # handling that may involve undefined references to
> @@ -709,6 +714,7 @@ libgcc_eh := -Wl,--as-needed -lgcc_s $(libunwind) -Wl,--no-as-needed
>  gnulib-arch =
>  gnulib = -lgcc $(gnulib-arch)
>  gnulib-tests := -lgcc $(libgcc_eh)
> +gnulib-extralibdir := $(shell $(CC) -print-libgcc-file-name | sed -e 's:/libgcc.*$$::')

>From gcc documentation [1], -print-libgcc-file-name is the same as -print-file-name=libgcc.a
which might be different than the place libgcc_s.so is installed.

On a toolchain built with build-many-glibc.py, I see:

$ arm-glibc-linux-gnueabihf-gcc -print-libgcc-file-name | xargs realpath
<path>/install/compilers/14/arm-linux-gnueabihf/lib/gcc/arm-glibc-linux-gnueabihf/14.2.1/libgcc.a

$ arm-glibc-linux-gnueabihf-gcc -print-file-name=libgcc_s.so | xargs realpath
<path>/install/compilers/14/arm-linux-gnueabihf/arm-glibc-linux-gnueabihf/lib/libgcc_s.so

So I think we should -print-file-name=libgcc_s.so instead here, and maybe 'dirname'
instead of sed (just to be a bit more clear).

>  static-gnulib-arch =
>  # By default, elf/static-stubs.o, instead of -lgcc_eh, is used to
>  # statically link programs.  When --disable-shared is used, we use
> @@ -781,10 +787,12 @@ endif
>  
>  # How to run a program we just linked with our library.
>  # The program binary is assumed to be $(word 2,$^).
> +# We may require additional libraries from gcc (e.g. libgcc_s.so for exception
> +# handling), which unfortunately somewhat breaks the isolation.
>  built-program-file = $(dir $(word 2,$^))$(notdir $(word 2,$^))
>  rtld-prefix = $(elf-objpfx)$(rtld-installed-name)			      \
>  	      --library-path						      \
> -	      $(rpath-link)$(patsubst %,:%,$(sysdep-library-path))
> +	      $(rpath-link)$(patsubst %,:%,$(sysdep-library-path)):$(gnulib-extralibdir)

It solves for the default case where tests are run explicit by issuing the loader,
we still need to add on RPATH for --enable-hardcoded-path-in-tests:

diff --git a/Makeconfig b/Makeconfig
index 6b4ebd1320..0008b8bec0 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -635,7 +635,7 @@ link-libc-printers-tests = $(link-libc-rpath) \
 # This is how to find at build-time things that will be installed there.
 rpath-dirs = math elf dlfcn nss nis rt resolv mathvec support
 rpath-link = \
-$(common-objdir):$(subst $(empty) ,:,$(patsubst ../$(subdir),.,$(rpath-dirs:%=$(common-objpfx)%)))
+$(common-objdir):$(subst $(empty) ,:,$(patsubst ../$(subdir),.,$(rpath-dirs:%=$(common-objpfx)%))):$(gnulib-extralibdir)
 else  # build-static
 link-libc = $(common-objpfx)libc.a $(otherlibs) $(gnulib) $(common-objpfx)libc.a $(gnulib)
 link-libc-tests = $(common-objpfx)libc.a $(otherlibs) $(gnulib-tests) $(common-objpfx)libc.a $(gnulib-tests)

>  ifeq (yes,$(build-shared))
>  comma = ,
>  sysdep-library-path = \

[1] https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html