GCC Bugzilla Bug 17608

When linking with -profile then -lc_p is used instead of -lc, and the former is 
only available as a static library.  Thus this should be treated like a static 
link, and no shared libgcc should be linked in.  But when HAVE_LD_AS_NEEDED 
then -lgcc_s is also being linked in by default, causing a shared link that 
uses both libc_p and libc, and the resulting binary will crash.

This is a target problem....

Postponed until GCC 3.4.4.

I suspect that -profile ought to always imply -static.  For instance, you can
get the same crash by linking with -profile and -lm, because libm.so needs libc.so.

On investigating, I'm convinced this is a linker bug.  When linking we use:
-lgcc --as-needed -lgcc_s --no-as-needed -lc_p -lgcc --as-needed -lgcc_s
--no-as-needed.

During the first scan of libgcc_s.so, the linker finds no reason to mark
libgcc_s.so as needed, because no symbols in libgcc_s.so are referenced at that
point.  After linking libc_p.a, the second scan of libgcc_s.so does find
referenced symbols.  However, the linker sees that these symbols have already
been defined, thus the "new" definitions found in the second scan of libgcc_s.so
aren't used.  (If a symbol is defined in two shared libs, the one from the lib
first encountered by the linker is used.  As far as the linker is concerned the
first libgcc_s.so is a different shared lib from the second libgcc_s.so).  Thus
the linker decides that the second libgcc_s.so isn't needed, and so doesn't emit
a DT_NEEDED tag for libgcc_s.so.

With older glibc ld.so, this resulted in segfaults.  Current ld.so complains with
 Inconsistency detected by ld.so: dl-version.c: 230: _dl_check_map_versions:
Assertion `needed != ((void *)0)' failed!

Fixed by http://sources.redhat.com/ml/binutils/2004-12/msg00272.html
Since this was a linker problem, the proper solution would be to add a configure
test for a fixed linker and only enable USE_LD_AS_NEEDED when a good linker is
found.  However, that would disable this linker feature for the normal (ie. non
-profile) case, breaking cancellation.