From: "Thomson, Patrick S" <patrick.s.thomson@intel.com>
To: <gdb@sources.redhat.com>
Subject: read_structure_type and virtual base types
Date: Wed, 13 Jul 2005 20:04:00 -0000 [thread overview]
Message-ID: <B6D265BA39581B46A91EA649F0A046020B80CFD1@azsmsx407> (raw)
Howdy Folks,
I'm attempting to use gdb 6.3 on an executable generated from the
latest intel c++ compiler (9.0). That particular compiler does not
generate child DIE information for member functions which are
declared but not implemented. If the class is a derived class and I
try to print an instantiated object of that class, gdb crashes.
I tracked what I think is the issue to
dwarf2read.c::read_structure_type().
At line read_structure_type()+119 we set TYPE_VPTR_BASETYPE(type),
but only if we have 1 or more member functions (see line
read_structure_type()+107 for fi.nfnfields test, this field is set at
line read_structure_type()+94).
Because I have no child DIEs for member functions, TYPE_VPTR_BASETYPE
remains 0, and I crash later on because this is eventually
dereferenced. Enough other data remains in the type structure to
indicate that the class is a derived class, so gdb expects
TYPE_VPTR_BASETYPE(type) to be set.
Since g++ does output the child die, this isn't generally a problem.
Ultimately my question is this: Is there a reason why the logic is
structured the way it is, and what is it? I can fix it easily enough
in my local copy by moving the closing brace for the
'if(fi.nfnfields){}' block so that it doesn't encompass the
DW_AT_containing_type attribute test a few lines later, but I'm not
sure what the consequences would be.
Thanks!
Pat Thomson
Intel Corporation
p.s. example class with associated DWARF DIE
class A : virtual public V{
int a;
int aa;
public:
void af(int); // declared, not implmented
};
Has the following DIE
<1><b64>: Abbrev Number: 17 (DW_TAG_class_type)
DW_AT_decl_line : 11
DW_AT_decl_column : 7
DW_AT_decl_file : 1
DW_AT_accessibility: 1 (public)
DW_AT_byte_size : 20
DW_AT_name : A
DW_AT_containing_type: <b64>
<2><b70>: Abbrev Number: 18 (DW_TAG_inheritance)
DW_AT_decl_line : 11
DW_AT_decl_column : 26
DW_AT_decl_file : 1
DW_AT_accessibility: 1 (public)
DW_AT_data_member_location: 7 byte block: 12 6 10 c 1c 6 22
(DW_OP_dup; DW_OP_deref; DW_OP_constu: 12; DW_OP_minus; DW_OP_deref;
DW_OP_plus)
DW_AT_type : <a75>
DW_AT_virtuality : 1 (virtual)
<2><b82>: Abbrev Number: 19 (DW_TAG_member)
DW_AT_name : _vptr.A
DW_AT_data_member_location: 2 byte block: 23 0
(DW_OP_plus_uconst: 0)
DW_AT_artificial : 1
DW_AT_type : <baf>
<2><b93>: Abbrev Number: 3 (DW_TAG_member)
DW_AT_decl_line : 12
DW_AT_decl_column : 9
DW_AT_decl_file : 1
DW_AT_data_member_location: 2 byte block: 23 4
(DW_OP_plus_uconst: 4)
DW_AT_name : a
DW_AT_type : <ab0>
<2><ba0>: Abbrev Number: 3 (DW_TAG_member)
DW_AT_decl_line : 13
DW_AT_decl_column : 9
DW_AT_decl_file : 1
DW_AT_data_member_location: 2 byte block: 23 8
(DW_OP_plus_uconst: 8)
DW_AT_name : aa
DW_AT_type : <ab0>
next reply other threads:[~2005-07-13 20:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-13 20:04 Thomson, Patrick S [this message]
2005-07-15 16:03 ` Kris Warkentin
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