Re: [PATCH 1/2] ltmain.in: ensure old libraries are not archived

[Alexandre Janniaux]

Hi,

For information, I've made a test project at this location:
https://github.com/alexandre-janniaux/libtool-relocatable-tests/blob/main/Makefile

It highlights the issue with the current libtool code and
show the linked result when using LIBTOOL=/path/to/patched/libtool.

I hope it helps review, but I can also improve it to test other
cases if needed.

Regards,
--
Alexandre Janniaux
Videolabs

On Tue, Apr 06, 2021 at 10:22:14AM +0200, Alexandre Janniaux wrote:
> Previously, adding a static archive library, aka. old library, as a
> dependency of a new libtool library compiled as a static archive (be it
> a convenience library or an installed static library) resulted in the
> dependency archive being added into the target archive as-is.
>
> However, linkers are usually not able to use nested archive as-is. It
> results in errors like these on Linux and Darwin at least:
>
>     /usr/bin/ld: ./.libs/libfoo.a: member ./.libs/libfoo.a(libbar.a) in
>     archive is not an object
>
> or
>
>     /usr/bin/nm: libbar.a: file format not recognized
>
> With libfoo.a being the static libtool target and libbar.a being the
> nested/linked static library.
>
> Libtool has a quite close behaviour with convenience libraries, where
> the content (objects) of the convenience library are extracted and added
> back into the new target, but that´s mostly a libtool creation.
>
> The static dependencies should not be "linked" into other static
> libraries as there should not be linking involved, and we don´t want to
> potentially duplicate symbols like done for the convenience libraries.
>
> Instead, keep them in the dependency_libs of the new libtool archive
> created and forward them until we link a shared library or an
> executable.
> ---
>  build-aux/ltmain.in | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/build-aux/ltmain.in b/build-aux/ltmain.in
> index 96b37003..d172deae 100644
> --- a/build-aux/ltmain.in
> +++ b/build-aux/ltmain.in
> @@ -5508,7 +5508,6 @@ func_mode_link ()
>        *.$libext)
>       # An archive.
>       func_append deplibs " $arg"
> -     func_append old_deplibs " $arg"
>       continue
>       ;;
>
> @@ -5867,6 +5866,8 @@ func_mode_link ()
>         if test conv = "$pass"; then
>           deplibs="$deplib $deplibs"
>           continue
> +       else
> +         func_append old_deplibs " $deplib"
>         fi
>         case $linkmode in
>         lib)
> @@ -6817,7 +6818,6 @@ func_mode_link ()
>        # Now set the variables for building old libraries.
>        build_libtool_libs=no
>        oldlibs=$output
> -      func_append objs "$old_deplibs"
>        ;;
>
>      lib)
> @@ -8697,7 +8697,11 @@ EOF
>         build_libtool_libs=no
>            ;;
>       *)
> -       oldobjs="$old_deplibs $non_pic_objects"
> +       oldobjs="$non_pic_objects"
> +       # This is not correct to add old_deplibs creating an archive
> +       # so append them only when creating an executable or a shared
> +       # library.
> +       test yes != "$build_old_libs" && oldobjs="$oldobjs $old_deplibs"
>         $preload && test -f "$symfileobj" \
>           && func_append oldobjs " $symfileobj"
>         addlibs=$old_convenience
> @@ -8958,6 +8962,7 @@ EOF
>           done
>           dlprefiles=$newdlprefiles
>         fi
> +       func_append dependency_libs " $old_deplibs"
>         $RM $output
>         # place dlname in correct position for cygwin
>         # In fact, it would be nice if we could use this code for all target
> --
> 2.31.1
>