[Bug target/17608] [3.3.4/3.4/4.0 regression] -profile should prevent use of libgcc_s

["amodra at bigpond dot net dot au" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From amodra at bigpond dot net dot au  2004-12-22 02:44 -------
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!

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17608