[Bug target/39578] Linkage broken for dllimport vtables

[Bug target/39578] Linkage broken for dllimport vtables

[ktietz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578

Kai Tietz <ktietz at gcc dot gnu.org> changed:

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

--- Comment #3 from Kai Tietz <ktietz at gcc dot gnu.org> ---
I retested issue for all open branches.  I can't reproduce issue anymore. 
Import library contains symbol for virtual.

If issue still exists please provide a testcase demonstrating that issue for
maintained branches still exists.

[Bug target/39578] Linkage broken for dllimport vtables

[tdragon at tdragon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578

--- Comment #4 from John E. / TDM <tdragon at tdragon dot net> ---
I can confirm this has been fixed. Sorry for not doing so sooner.

[Bug target/39578] New: Linkage broken for dllimport vtables

[tdragon at tdragon dot net]

The linkage for the vtable for any class marked dllimport is generated as a
standard external link rather than a dllimport "__imp_" link. This results in
linker diagnostics such as:

Info: resolving vtable for TestObject by linking to __imp___ZTV10TestObject
(auto-import)
d:/jsupport/mingw/bin/../lib/gcc/mingw32/4.3.3-dw2/../../../../mingw32/bin/ld.exe:
warning: auto-importing has been activated without --enable-auto-import
specified on the command line.
This should work unless it involves constant data structures referencing
symbols from auto-imported DLLs.

The following simple testcase demonstrates this.

----- vttest.cpp -----
struct __attribute__((dllimport)) TestObject
{
        virtual void VirtFunc();
};
int main()
{
        TestObject obj;
        obj.VirtFunc();
        return 0;
}

----- vttestdll.cpp -----
struct __attribute__((dllexport)) TestObject
{
        virtual void VirtFunc() {}
};

> g++ -shared -o vttest.dll -Wl,--out-implib,libvttest.dll.a vttestdll.cpp
Creating library file: libvttest.a
> g++ -o vttest.exe vttest.cpp libvttest.dll.a
Info: resolving vtable for TestObject by linking to __imp___ZTV10TestObject
(auto-import)
d:/jsupport/mingw/bin/../lib/gcc/mingw32/4.3.3-dw2/../../../../mingw32/bin/ld.exe:
warning: auto-importing has been activated without --enable-auto-import
specified on the command line.
This should work unless it involves constant data structures referencing
symbols from auto-imported DLLs.


-- 
           Summary: Linkage broken for dllimport vtables
           Product: gcc
           Version: 4.3.3
            Status: UNCONFIRMED
          Severity: critical
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tdragon at tdragon dot net
 GCC build triplet: mingw32
  GCC host triplet: mingw32
GCC target triplet: mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578

[Bug target/39578] Linkage broken for dllimport vtables

[dave dot korn dot cygwin at gmail dot com]

------- Comment #1 from dave dot korn dot cygwin at gmail dot com  2009-03-29 17:47 -------
For Cygwin, we just recently made --enable-auto-import the default in CVS
binutils.  Now that we're moving to shared library runtimes throughout it made
sense.

However, I think this is a real bug, as it doesn't happen on 4.3.2; we get a
direct undefined reference to the import symbol in the object file:

$ g++ -g -o vttest.exe vttest.cpp libvttest.dll.a --save-temps

admin@ubik /tmp/vttest
$ nm vttest.o
00000000 b .bss
00000000 d .data
00000000 N .debug_abbrev
00000000 N .debug_aranges
00000000 N .debug_frame
00000000 N .debug_info
00000000 N .debug_line
00000000 N .debug_loc
00000000 N .debug_pubnames
00000000 N .debug_ranges
00000000 N .debug_str
00000000 d .eh_frame
00000000 t .text
00000000 t .text$_ZN10TestObjectC1Ev
00000000 T __ZN10TestObjectC1Ev
         U ___gxx_personality_v0
         U ___main
         U __imp___ZN10TestObject8VirtFuncEv
         U __imp___ZTV10TestObject
00000000 T _main

admin@ubik /tmp/vttest
$ 

My earlier build of 4.3.3 with the patch for PR36654 reverted does the same
thing.  However, as soon as I reapplied the patch and rebuilt cc1plus, I got
this output:

/tmp/vttest $ nm vttest.o    libvtt
00000000 b .bss
00000000 d .data
00000000 N .debug_abbrev
00000000 N .debug_aranges
00000000 N .debug_frame
00000000 N .debug_info
00000000 N .debug_line
00000000 N .debug_loc
00000000 N .debug_pubnames
00000000 N .debug_ranges
00000000 N .debug_str
00000000 d .eh_frame
00000000 t .text
00000000 t .text$_ZN10TestObjectC1Ev
00000000 T __ZN10TestObjectC1Ev
         U __ZTV10TestObject
         U ___gxx_personality_v0
         U ___main
         U __imp___ZN10TestObject8VirtFuncEv
00000000 T _main
/tmp/vttest $

So I think that confirms it.


-- 

dave dot korn dot cygwin at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dave dot korn dot cygwin at
                   |                            |gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578

[Bug target/39578] Linkage broken for dllimport vtables

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|critical                    |normal


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578

[Bug target/39578] Linkage broken for dllimport vtables

[ktietz at gcc dot gnu dot org]

------- Comment #2 from ktietz at gcc dot gnu dot org  2009-09-12 09:54 -------
I tested this bug for 4.5 and here it seems to be solved for i686-pc-mingw32.


-- 

ktietz at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ktietz at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39578