[Bug c++/47218] New: [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[Bug c++/47218] New: [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

           Summary: [4.6.0 regression] C++ multiple definitions of
                    non-virtual thunk problem
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: davek@gcc.gnu.org


Sometime between 2010-12-22 and rev.167484, something changed in the behaviour
of the C++ compiler w.r.t the way it handles non-virtual thunks.  I have just
discovered this while working on a patch for PR43601; a compiler built from
trunk on the earlier date reproduces the problem described there, ending in an
out-of-memory error during the final link:

Creating library file:
/tmp/wx/obj-x-ming-new/lib/libwx_mswd_core-2.8.dll.a/opt/
mingw-new/lib/gcc/i686-pc-mingw32/4.6.0/../../../../i686-pc-mingw32/bin/ld:
fina
l link failed: Memory exhausted
collect2: ld returned 1 exit status


... whereas a compiler built from r.167484 emits a whole lot of
multiple-definition errors, and stops before trying to complete the link:

Creating library file:
/tmp/wx/obj-x-ming-clean/lib/libwx_based-2.8.dll.abasedll_wfstream.o:/tmp/wx/wxWidgets-2.8.11/src/common/wfstream.cpp:407:
multiple definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_wfstream.o:/tmp/wx/wxWidgets-2.8.11/src/common/wfstream.cpp:407:
multiple definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_wfstream.o:/tmp/wx/wxWidgets-2.8.11/src/common/wfstream.cpp:407:
multiple definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_wfstream.o:/tmp/wx/wxWidgets-2.8.11/src/common/wfstream.cpp:407:
multiple definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_zipstrm.o:/tmp/wx/wxWidgets-2.8.11/src/common/zipstrm.cpp:2423:
multiple definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_zipstrm.o:/tmp/wx/wxWidgets-2.8.11/src/common/zipstrm.cpp:2423:
multiple definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_zipstrm.o:/tmp/wx/wxWidgets-2.8.11/src/common/zipstrm.cpp:2423:
multiple definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_zipstrm.o:/tmp/wx/wxWidgets-2.8.11/src/common/zipstrm.cpp:2423:
multiple definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_registry.o:/tmp/wx/wxWidgets-2.8.11/src/msw/registry.cpp:1428: multiple
definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_registry.o:/tmp/wx/wxWidgets-2.8.11/src/msw/registry.cpp:1428: multiple
definition of `non-virtual thunk to wxFFileStream::~wxFFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_registry.o:/tmp/wx/wxWidgets-2.8.11/src/msw/registry.cpp:1428: multiple
definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
basedll_registry.o:/tmp/wx/wxWidgets-2.8.11/src/msw/registry.cpp:1428: multiple
definition of `non-virtual thunk to wxFileStream::~wxFileStream()'
basedll_filesys.o:/tmp/wx/wxWidgets-2.8.11/src/common/filesys.cpp:697: first
defined here
collect2: ld returned 1 exit status

In both cases the build was configured with a cygwin-x-mingw cross compiler
using the same command line:

$ /tmp/wx/wxWidgets-2.8.11/configure --with-msw --enable-debug
--enable-debug_gdb --enable-shared 2>&1 --host=i686-pc-mingw32 

More once I've diagnosed what's going on in some of the generated object files.
 I've marked this major as it could easily affect a whole lot of c++ library
builds, but may reduce that severity if it turns out to be something unusual
that wx is doing.  However it's still a regression.

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

Dave Korn <davek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.01.07 21:05:02
     Ever Confirmed|0                           |1

--- Comment #1 from Dave Korn <davek at gcc dot gnu.org> 2011-01-07 21:05:02 UTC ---
Yeah, confirmed that.  With the older compiler the NVT is emitted in a comdat
section as you'd expect: the symbols ...

[6421](sec 2101)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000000
__ZThn32_N13wxFFileStreamD1Ev
[6427](sec 2103)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000000
__ZThn32_N13wxFFileStreamD0Ev

... point to sections (note MS numbers sections from 1, objdump from zero) like
so:

2100 .text$_ZThn32_N13wxFFileStreamD1Ev 0000000c  00000000  00000000  0002d368 
2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE,
LINK_ONCE_DISCARD (COMDAT __ZThn32_N13wxFFileStreamD1Ev 6421)

2102 .text$_ZThn32_N13wxFFileStreamD0Ev 0000000c  00000000  00000000  0002d3e0 
2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE,
LINK_ONCE_DISCARD (COMDAT __ZThn32_N13wxFFileStreamD0Ev 6427)

With the latest trunk however, the same symbols ... 

[6419](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000fa8
__ZThn32_N13wxFFileStreamD1Ev
[6423](sec  1)(fl 0x00)(ty  20)(scl   2) (nx 0) 0x00000fb2
__ZThn32_N13wxFFileStreamD0Ev

... both point to section 1: the .text section.

  0 .text         00000fd0  00000000  00000000  0001633c  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE


This being replicated across all object files, no wonder we have multiple
defintion errors.  It's a bug that the NVT doesn't get emitted in a comdat, I
expect.

(I think I remember some kind of recent change to section handling that I saw
fly past on the patches list, wonder if it could be related.)

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[silver24k at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

Yu Simin <silver24k at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |silver24k at gmail dot com

--- Comment #2 from Yu Simin <silver24k at gmail dot com> 2011-01-08 15:12:12 UTC ---
*** Bug 47116 has been marked as a duplicate of this bug. ***

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[silver24k at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #3 from Yu Simin <silver24k at gmail dot com> 2011-01-08 15:13:42 UTC ---
A simple test in PR47116:
http://gcc.gnu.org/bugzilla/attachment.cgi?id=22866

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #4 from Dave Korn <davek at gcc dot gnu.org> 2011-01-08 16:35:31 UTC ---
(In reply to comment #3)
> A simple test in PR47116:
> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22866


Thankyou, that should make debugging it easier :)

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #5 from Dave Korn <davek at gcc dot gnu.org> 2011-01-08 18:06:07 UTC ---
Bug is caused by the change at rev 167795 applied to fix PR46667.

http://gcc.gnu.org/viewcvs?view=revision&revision=167795

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #6 from Dave Korn <davek at gcc dot gnu.org> 2011-01-08 19:00:25 UTC ---
(In reply to comment #5)
> Bug is caused by the change at rev 167795 applied to fix PR46667.
> 
> http://gcc.gnu.org/viewcvs?view=revision&revision=167795

Full details at http://gcc.gnu.org/ml/gcc-patches/2011-01/msg00446.html:

>"  It turns out that resolve_unique_function() is not called at all for the
thunk function any more, where previously it was called from
assemble_start_function called from cgraph_expand_function.  This is because
gimple_expand_cfg() isn't called for these thunk functions; they are emitted
through a call chain that looks like:

> (gdb) bt
> #0  assemble_start_function (decl=0x7fe32f00,
>     fnname=0x7fe41860 "_ZThn4_N7FooBase3BarEv")
>     at /gnu/gcc/gcc-patched/gcc/varasm.c:1524
> #1  0x007aa73c in cgraph_expand_function (node=0x7ff80c30)
>     at /gnu/gcc/gcc-patched/gcc/cgraphunit.c:1328
> #2  0x007ad210 in cgraph_optimize ()
>     at /gnu/gcc/gcc-patched/gcc/cgraphunit.c:1567
> #3  0x007ad69a in cgraph_finalize_compilation_unit ()
>     at /gnu/gcc/gcc-patched/gcc/cgraphunit.c:1031
> #4  0x004ce825 in cp_write_global_declarations ()
>     at /gnu/gcc/gcc-patched/gcc/cp/decl2.c:3974
> #5  0x0080ed6d in toplev_main (argc=14, argv=0x5079f78)
>     at /gnu/gcc/gcc-patched/gcc/toplev.c:591
> #6  0x0060699f in main (argc=Cannot access memory at address 0x0
> ) at /gnu/gcc/gcc-patched/gcc/main.c:36  "

That's the main part of it.

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

Dave Korn <davek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #7 from Dave Korn <davek at gcc dot gnu.org> 2011-01-09 00:47:15 UTC ---
Created attachment 22932
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22932
proposed patch

Ensures thunks get a section name assigned in cgraphunit.c#assemble_thunk(). 
Taking this for a bootstrap/test cycle.

Re: [Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[Jan Hubicka]

Consider the patch pre-approved if it passes testing.  Thanks!

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[hubicka at ucw dot cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #8 from Jan Hubicka <hubicka at ucw dot cz> 2011-01-09 00:57:12 UTC ---
Consider the patch pre-approved if it passes testing.  Thanks!

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

--- Comment #9 from Dave Korn <davek at gcc dot gnu.org> 2011-01-10 00:33:35 UTC ---
Author: davek
Date: Mon Jan 10 00:33:32 2011
New Revision: 168624

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=168624
Log:
gcc/ChangeLog:

    PR c++/47218
    * cgraphunit.c (assemble_thunk): Call resolve_unique_section.

gcc/testsuite/ChangeLog:

    PR c++/47218
    * g++.dg/other/pr47218-1.C: New test file.
    * g++.dg/other/pr47218.C: Likewise.
    * g++.dg/other/pr47218.h: New supporting header.


Added:
    trunk/gcc/testsuite/g++.dg/other/pr47218-1.C
    trunk/gcc/testsuite/g++.dg/other/pr47218.C
    trunk/gcc/testsuite/g++.dg/other/pr47218.h
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cgraphunit.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/47218] [4.6.0 regression] C++ multiple definitions of non-virtual thunk problem

[davek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

Dave Korn <davek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #10 from Dave Korn <davek at gcc dot gnu.org> 2011-01-10 00:53:45 UTC ---
Done.

[Bug c++/47218] [4.6 regression] C++ multiple definitions of non-virtual thunk problem

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47218

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.6.0
            Summary|[4.6.0 regression] C++      |[4.6 regression] C++
                   |multiple definitions of     |multiple definitions of
                   |non-virtual thunk problem   |non-virtual thunk problem