When building qt-3.3.8 and wxGTk on Tru64 UNIX 5.1
(alphaev67-dec-osf5.1) with gcc-4.2.4, we got linker failures about
duplicate non-virtual thunks, e.g. from qt:
/usr/ccs/bin/ld:
.obj/release-shared-mt/qmotifdnd_x11.o: non-virtual thunk to
QDragMoveEvent::~QDragMoveEvent(): multiply defined
.obj/release-shared-mt/qmotifdnd_x11.o: non-virtual thunk to
QDragMoveEvent::~QDragMoveEvent(): multiply defined
.obj/release-shared-mt/qmotifdnd_x11.o: non-virtual thunk to
QDragEnterEvent::~QDragEnterEvent(): multiply defined
.obj/release-shared-mt/qmotifdnd_x11.o: non-virtual thunk to
QDragEnterEvent::~QDragEnterEvent(): multiply defined
This appears to be because the non-virtual thunks are not output weak on this
platform, so, those that appear in multiple objects will cause linker errors
like this (in the above case, there are _ZThn16_N14QDragMoveEventD0Ev and
_ZThn16_N14QDragMoveEventD1Ev in both qdnd_x11.o and qmotifdnd_x11.o).
This is easily reproducible, for example, compiling a slightly modified version
of dllexport-MI1.C from the g++ testsuite.
With gcc-4.2.4:
% g++ -c -o dllexport-MI1.o dllexport-MI1.C; nm -wB dllexport-MI1.o | grep Thn
0x00000000000000 N $_ZThn8_N3MI1D0Ev..ng
0x00000000000000 N $_ZThn8_N3MI1D1Ev..ng
0x00000000000000 N $_ZThn8_NK3MI12vfEv..ng
0x00000000000854 T _ZThn8_N3MI1D0Ev
0x00000000000910 T _ZThn8_N3MI1D1Ev
0x00000000000208 T _ZThn8_NK3MI12vfEv
When compared to gcc-3.4.3:
g++ -c -o dllexport-MI1.o dllexport-MI1.C; nm -wB dllexport-MI1.o | grep Thn
0x00000000000000 N $_ZThn8_N3MI1D0Ev..ng
0x00000000000000 N $_ZThn8_N3MI1D1Ev..ng
0x00000000000000 N $_ZThn8_NK3MI12vfEv..ng
0x00000000000344 T* _ZThn8_N3MI1D0Ev
0x00000000000548 T* _ZThn8_N3MI1D1Ev
0x000000000001f0 T* _ZThn8_NK3MI12vfEv
The '*' in the nm output indicates a weak symbol.
--
Summary: Tru64 outputs non-virtual thunks as non-weak symbols
Product: gcc
Version: 4.2.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bugzilla-gcc at thewrittenword dot com
GCC host triplet: alphaev67-dec-osf5.1
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38581
