http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55171
Bug #: 55171 Summary: incorrect virtual thunk on mingw Classification: Unclassified Product: gcc Version: 4.7.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassig...@gcc.gnu.org ReportedBy: mi...@ociweb.com Created attachment 28593 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28593 test for virtual call on mingw When a virtual call invoked on an object which uses both virtual and non-virtual inheritance, the virtual thunk leaves the target function with an invalid "this" pointer. Attached test fails with output: created Derived object at: 0x2c1a50 Derived virtual call at: 0x409800 Assertion failed! >From gdb: In the body of the most-derived constructor (gdb) inf vt this vtable for 'Derived' @ 0x4097ec (subobject @ 0x2c1a50): [0]: 0x40188a <Derived::~Derived()> [1]: 0x40190a <Derived::~Derived()> [2]: 0x401932 <Derived::foo() const> vtable for 'VirtBase' @ 0x409808 (subobject @ 0x2c1a58): [0]: 0x401902 <virtual thunk to Derived::~Derived()> [1]: 0x40192a <virtual thunk to Derived::~Derived()> [2]: 0x4019d1 <virtual thunk to Derived::foo() const> 0x004019d1 in virtual thunk to Derived::foo() const () at gccbug.cpp:45 Dump of assembler code for function _ZTv0_n16_NK7Derived3fooEv: => 0x004019d1 <+0>: mov 0x4(%esp),%eax 0x004019d5 <+4>: mov (%eax),%eax 0x004019d7 <+6>: add -0x10(%eax),%eax 0x004019da <+9>: mov %eax,0x4(%esp) 0x004019de <+13>: jmp 0x401932 <Derived::foo() const> After thunk has jumped to target function Derived::foo (this=0x409800) at gccbug.cpp:41 41 { (gdb) inf vt this Cannot access memory at address 0xffffffec