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From: "amodra at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/64163] [5 Regression] r218024 causes qt5 build failure
Date: Wed, 03 Dec 2014 22:18:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64163

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amodra at gmail dot com

--- Comment #6 from Alan Modra <amodra at gmail dot com> ---
No, this is not a gold bug on x86_64.  ld.bfd may link without complaint, but
the resulting shared library will crash, I think.  There are calls to
_ZN5QListI7QStringED1Ev which resolve to 0 (ie. the ELF header in the shared
lib).

This seems to be a fairly recent bug.  On x86_64, 20141126 and 20141203
miscompile the unreduced testcase while 20141111 looks to be OK.  You can
easily see whether there is a problme by running

nm *.o | grep _ZN5QListI7QStringED
0000000000000000 W _ZN5QListI7QStringED2Ev
0000000000000000 n _ZN5QListI7QStringED5Ev
0000000000000000 W _ZN5QListI7QStringED1Ev
0000000000000000 W _ZN5QListI7QStringED2Ev
0000000000000000 n _ZN5QListI7QStringED5Ev

If as above you see only one copy of _ZN5QListI7QStringED1Ev, then only one of
the two comdat groups define that symbol.