https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65189
Bug ID: 65189
Summary: Malformed (C++) class-hierarchy dump on abstract class
(in comparission to GCC 4.6.x)
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: meisenmann....@fh-salzburg.ac.at
Following minimal sample (Ie. test.cpp) does generate a noticeable different
class-hierarchy dump with GCC 4.9.2 - compared to GCC 4.6.4:
class A
{
public:
virtual ~A();
virtual int getVal() const = 0;
};
Calling
gcc -c -fdump-classhierarchy test.cpp && type test.cpp.002t.class
a) generates with GCC 4.6.4 (as expected):
Vtable for A
A::_ZTV1A: 5u entries
0 (int (*)(...))0
4 (int (*)(...))(& _ZTI1A)
8 (int (*)(...))A::~A
12 (int (*)(...))A::~A
16 (int (*)(...))__cxa_pure_virtual
Class A .. dropped; Ie. no difference
b) with GCC 4.9.2, the output is
A::_ZTV1A: 5u entries
0 (int (*)(...))0
4 (int (*)(...))(& _ZTI1A)
8 (int (*)(...))0u
12 (int (*)(...))0u
16 (int (*)(...))__cxa_pure_virtual
The two d'tor-entries (offset 8 and 12) are 0u ?!
This issue also affects the generated dump with option
"-fdump-translation-unit"
... which is used by the ABI Compliance Checker (ABICC).
For example, if I compare the ABI-compatibility of abstract classes between
different GCC-versions, a incorrect/false-positive mismatch of the vtable
(concerning the virtual d'tor entries) is determined.
I've already tested some additional options to dtermine a work-around, but
without luck!
Best regards from Salzburg,
Markus
