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Date: Fri, 24 Jan 2003 15:22:00 -0000
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To: gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org,
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From: bangerth@dealii.org
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Subject: Re: c++/9433: [3.2/3.3/3.4 regression] SegFault in dynamic_cast
X-SW-Source: 2003-01/txt/msg01420.txt.bz2
List-Id: <gcc-prs.sourceware.org>

Old Synopsis: memory fault
New Synopsis: [3.2/3.3/3.4 regression] SegFault in dynamic_cast

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Jan 24 15:22:42 2003
State-Changed-Why:
    Confirmed (one x86 linux). It used to work with 2.95, but is broken in
    3.2, 3.3, and 3.4 branches/CVS. The following slightly
    simplified testcase shows the same behavior (the class
    hierarchy is an exercise in applied graph theory :-)
    -------------------------------
    struct A        { virtual ~A() {}; };
    struct B        {};
    struct C : A, B {};
    struct D : C    {};
    struct E : C    {};
    struct F : protected D, E {};
    struct H : virtual F {};
    struct I : H    {};
    struct J : H    {};
    struct K : I, J {};
    struct M : K    {};
    struct N : M    {};
    struct O : M    {};
    struct P : N, O {};
    
    int main() {
      P obj;
      A* a1 = (D*)&obj;
      dynamic_cast<H*>(a1);
    }
    -------------------------------
    The Segfault happens in the runtime support libs (with 3.4):
    
    (gdb) bt
    #0  0x4006c7a2 in __cxxabiv1::__vmi_class_type_info::__do_find_public_src(int, void const*, __cxxabiv1::__class_type_info const*, void const*) const (
        this=0x804a4a0, src2dst=-1, obj_ptr=0x0, src_type=0x804a488, 
        src_ptr=0xbffff184)
        at ../../../../gcc-3.4-CVS/libstdc++-v3/libsupc++/tinfo.cc:122
    #1  0x4006cd0d in __cxxabiv1::__vmi_class_type_info::__do_dyncast(int, __cxxabiv1::__class_type_info::__sub_kind, __cxxabiv1::__class_type_info const*, void const*, __cxxabiv1::__class_type_info const*, void const*, __cxxabiv1::__class_type_info::__dyncast_result&) const (this=0x804ab60, src2dst=-1, 
        access_path=__contained_public, dst_type=0x804a4a0, obj_ptr=0xbffff174, 
        src_type=0x804a488, src_ptr=0xbffff184, result=@0xbffff120)
        at ../../../../gcc-3.4-CVS/libstdc++-v3/libsupc++/tinfo.cc:264
    #2  0x4006d0c3 in __dynamic_cast (src_ptr=0xbffff184, src_type=0x804a488, 
        dst_type=0x804a4a0, src2dst=-1)
        at ../../../../gcc-3.4-CVS/libstdc++-v3/libsupc++/tinfo.cc:712
    #3  0x08048703 in main () at x.cc:19
    
    W.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9433