[Bug ld/16452] New: ELF executable with weak reference linked with ld causes assertion in ld.so

[brnguyen at nvidia dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=16452

            Bug ID: 16452
           Summary: ELF executable with weak reference linked with ld
                    causes assertion in ld.so
           Product: binutils
           Version: 2.25 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: brnguyen at nvidia dot com

Created attachment 7357
  --> http://sourceware.org/bugzilla/attachment.cgi?id=7357&action=edit
Reproduction test case

The attached reproduction test case builds two DSOs, one linked against
pthreads, and one not linked against pthreads, which implement the same
interface.  It also builds a test application which is linked against the DSO
that uses pthreads.  To reproduce the bug, the DSO that does not use pthreads
is copied over the DSO that uses pthreads, and the test application is run.

Using an ld built from commit 08d0cad39e31083cb8a885703604f7b20d359849, this
triggers the following assertion on ld.so built from commit
2f10c4d6901e7a4c4ad294cc5bb8ece6547f4f62 as well as ld.so from glibc
2.15-0ubuntu10.5-ppa1 on my Ubuntu 12.04 LTS system:

Inconsistency detected by ld.so: dl-version.c: 224: _dl_check_map_versions:
Assertion `needed != ((void *)0)' failed!

This may be related to bugs #15149 and #12549. Also relevant is Debian bug
#728529.

This appears to be a regression in ld (though there may be a bug in ld.so as
well). I bisected binutils using this reproduction test case to try to narrow
down the commit(s) responsible for this regression. Interestingly, ld fails to
link the test executable in a commit range between ToT master and
binutils_2.22, with the following error messages:

/home/brnguyen/build/binutils//ld/ld: /tmp/cc3K1rHK.o: undefined reference to
symbol 'pthread_create@@GLIBC_2.2.5'
/home/brnguyen/build/binutils//ld/ld: note: 'pthread_create@@GLIBC_2.2.5' is
defined in DSO //lib/x86_64-linux-gnu/libpthread.so.0 so try adding it to the
linker command line

It appears this link error was introduced by commit
b64fb44af4f416fbbbda3de03fcfff61d80c841c ("Also track weak references") and
later removed by commit 879707c642925947e156b7ae2169b89f844532cd ("Exclude weak
refs when considering whether an --as-needed library is needed"), at which
point ld produces an executable which triggers the assertion.

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