Re: Help: GOLD unable to find logf() in libm.so when sysroot is enabled

[Ian Lance Taylor <iant at google dot com>]

On Thu, Nov 3, 2016 at 3:15 AM, Nick Clifton <nickc@redhat.com> wrote:
>
>   Do you have a minute to help me with a Fedora binutils bug which I
>   think might be a generic GOLD problem ?
>
>     https://bugzilla.redhat.com/show_bug.cgi?id=1386126
>
>   The problem appears to be that an ARM native GOLD linker built with
>   --with-sysroot=/ enabled reports that it cannot resolve a reference to
>   the logf symbol (in libm.so), despite the fact that it has found the
>   library:
>
>   SYSROOT GOLD
> /usr/lib/ghc-7.10.3/text_HmqVQnZSpjaC156ABqPhne/libHStext-1.2.2.1-HmqVQnZSpjaC156ABqPhne-ghc7.10.3.so: reference to logf
> /usr/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM-ghc7.10.3.so: reference to logf
> /usr/lib/ghc-7.10.3/ghcpr_8TmvWUcS1U1IKHT0levwg3/libHSghc-prim-0.4.0.0-8TmvWUcS1U1IKHT0levwg3-ghc7.10.3.so: reference to logf
> /usr/lib/gcc/armv7hl-redhat-linux-gnueabi/6.2.1/../../../libm.so: definition of logf
> /usr/lib/ghc-7.10.3/text_HmqVQnZSpjaC156ABqPhne/libHStext-1.2.2.1-HmqVQnZSpjaC156ABqPhne-ghc7.10.3.so: error: undefined reference to 'logf'
>
>   NON-SYSROOT GOLD
> /usr/lib/ghc-7.10.3/text_HmqVQnZSpjaC156ABqPhne/libHStext-1.2.2.1-HmqVQnZSpjaC156ABqPhne-ghc7.10.3.so: reference to logf
> /usr/lib/ghc-7.10.3/base_HQfYBxpPvuw8OunzQu6JGM/libHSbase-4.8.2.0-HQfYBxpPvuw8OunzQu6JGM-ghc7.10.3.so: reference to logf
> /usr/lib/ghc-7.10.3/ghcpr_8TmvWUcS1U1IKHT0levwg3/libHSghc-prim-0.4.0.0-8TmvWUcS1U1IKHT0levwg3-ghc7.10.3.so: reference to logf
> /usr/lib/gcc/armv7hl-redhat-linux-gnueabi/6.2.1/../../../libm.so: definition of logf
>
>   Apparently this problem is restricted to the ARM and AARCH64 targets,
>   although I have not verified this.  It may be a factor of the build
>   systems involved, in that the build for non-arm targets might use a
>   different location for the application libraries.  That is just a
>   guess however.
>
>   Also I do not know if the logf symbol is special, or it just happens
>   that this is the only symbol in libm.so that is needed by the
>   libHStext-1.2.2.1-HmqVQnZSpjaC156ABqPhne-ghc7.10.3.so library.  I
>   suspect the latter however.
>
>   I have found that if I add a second reference to logf in an ordinary
>   object file that the link then works.

gold only warns about undefined references from shared libraries in
specific circumstances.  See
Symbol_table::warn_about_undefined_dynobj_symbol in symtab.cc.  I
think that particularly relevant here is that gold does not warn about
an undefined reference in a shared library that it finds in a "system
directory", which basically means a directory found in the sysroot.
I'm guessing that that is somehow the difference between your two
links.  But I don't know why the definition of logf found in libm.so
is not satisfying the references from the other shared libraries.
Could there be any versions involved?

Ian