[Bug lto/84995] New: Documentation gcc-ar and gcc-ranlib vs {libdir}/bfd-plugins

[dilyan.palauzov at aegee dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84995

            Bug ID: 84995
           Summary: Documentation gcc-ar and gcc-ranlib vs
                    {libdir}/bfd-plugins
           Product: gcc
           Version: 7.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dilyan.palauzov at aegee dot org
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

While ar, ranlib and nm work with LTO, if the plugin is installed in
{libdir}/bfd-plugin, the gcc manual (Optimizing options) recommends the use of
gcc-ar and gcc-ranlib.

Why doesn't the manual recommend installing instead the plugin under
/bfd-plugin?  

Providing that both gcc and clang offer LTO and provide linker plugins, none of
them installs by default the plugins under {libdir}/bfd-plugins, gcc recommends
the usage of gcc-ar/gcc-ranlib, clang installs instead clang-ar/clang-ranlib,
how are ./configure scripts supposed to be written in portable way to enable
LTO compilation?

If several gcc versions are installed on a system and hence
/usr/local/libexec/gcc/x86_64-pc-linux-gnu/7.3.1/liblto_plugin.so.0.0.0 and
/usr/local/libexec/gcc/x86_64-pc-linux-gnu/6.4.1/liblto_plugin.so.0.0.0
co-exist, will gcc-ar always use
/gcc/x86_64-pc-linux-gnu/6.4.1/liblto_plugin.so.0.0.0, if the code is compiled
with x86_64-pc-linux-gnu-gcc-6.4.1?