Re: Mangled Typedef names in GNU 4.1.2 DWARF data?
The use of anonymous structure does seem to be the problem. I also missed the
fact that the TYPE_DEF DIE is missing from the DWARF data. If the TYPE
_DEF DIE was in the DWARF data, I could still parse the anonymous type.
Do you think the TYPE_DEF DIE should be part of the output? Is this a GNU
bug or just an unsupported feature?
Thanks.
--- On Fri, 1/22/10, Michael Eager wrote:
> From: Michael Eager
> Subject: Re: Mangled Typedef names in GNU 4.1.2 DWARF data?
> To: "Ron Louzon"
> Cc: gcc@gcc.gnu.org
> Date: Friday, January 22, 2010, 4:39 PM
> Ron Louzon wrote:
> > The GNU 4.1.2 C++ compiler is mangling typedef names
> to the point that they are not retrievable from the DWARF
> data.
> >
> > For example, the type BASE_UNION is defined as
> >
> > typedef union
> > {
> > char ch;
> > int iVal;
> > long IVal;
> > } BASE_UNION;
>
> This is an anonymous union which is typedef'ed to
> BASE_UNION.
>
> >
> > The GNU 4.1.2 compiler generates the following DWARF
> data for this type
> >
> > <1><1279>: Abbrev Number: 35
> (DW_TAG_union_type)
> > <127a>
> DW_AT_sibling :
> <12a8>
> > <127e>
> DW_AT_name :
> $_4
> > <1282>
> DW_AT_byte_size :
> 4
> > <1283>
> DW_AT_decl_file :
> 35
> > <1284>
> DW_AT_decl_line :
> 29
>
> This doesn't look correct. The union has no name, so
> DW_AT_name should
> not be present or should be null. From the DWARF v.3
> spec:
>
> 2.15 Identifier Names
>
> Any debugging information entry representing a
> program entity that has been
> given a name may have a DW_AT_name attribute, whose
> value is a string
> representing the name as it appears in the source
> program. A debugging
> information entry containing no name attribute, or
> containing a name attribute
> whose value consists of a name containing a single
> null byte, represents a
> program entity for which no name was given in the
> source.
>
> > <2><1285>: Abbrev Number: 36
> (DW_TAG_member)
> > <1286>
> DW_AT_name :
> ch
> > <1289>
> DW_AT_decl_file :
> 35
> > <128a>
> DW_AT_decl_line :
> 30
> > <128b>
> DW_AT_type :
>
> > <2><128f>: Abbrev Number: 36
> (DW_TAG_member)
> > <1290>
> DW_AT_name :
> iVal
> > <1295>
> DW_AT_decl_file :
> 35
> > <1296>
> DW_AT_decl_line :
> 31
> > <1297>
> DW_AT_type :
>
> > <2><129b>: Abbrev Number: 36
> (DW_TAG_member)
> > <129c>
> DW_AT_name :
> IVal
> > <12a1>
> DW_AT_decl_file :
> 35
> > <12a2>
> DW_AT_decl_line :
> 32
> > <12a3>
> DW_AT_type :
>
> >
> > Notice that the union name has been changed to "$_4"
> in DIE <1279>.
> >
> > The GNU 3.4.4 compiler generates the following DWARF
> data from the same source code:
> >
> > <1><11d0>: Abbrev Number: 27
> (DW_TAG_union_type)
> > DW_AT_sibling
> : <123f>
> > DW_AT_name
> : (indirect string, offset: 0x6e):
> BASE_UNION
> > DW_AT_byte_size :
> 4
> > DW_AT_decl_file :
> 3
> > DW_AT_decl_line :
> 29
>
> This is similarly incorrect. The union has no name.
>
>
> > Why is GNU 4.1.2 generating the mangled type name and
> how do I correct this to generate the real type name?
>
> A better question might by why there is no DW_TAG_typedef
> DIE which looks like
>
> DW_TAG_typedef
>
> DW_AT_name: BASE_UNION
>
> DW_AT_type: <1279>
>
> BTW gcc-4.3.2 generates
>
> DW_AT_name:
>
> which is also incorrect.
>
>
>
> -- Michael eager ea...@eagercon.com
> 1960 Park Blvd., Palo Alto, CA 94306 650-325-8077
>
Mangled Typedef names in GNU 4.1.2 DWARF data?
The GNU 4.1.2 C++ compiler is mangling typedef names to the point that they are
not retrievable from the DWARF data.
For example, the type BASE_UNION is defined as
typedef union
{
char ch;
int iVal;
long IVal;
} BASE_UNION;
The GNU 4.1.2 compiler generates the following DWARF data for this type
<1><1279>: Abbrev Number: 35 (DW_TAG_union_type)
<127a> DW_AT_sibling : <12a8>
<127e> DW_AT_name: $_4
<1282> DW_AT_byte_size : 4
<1283> DW_AT_decl_file : 35
<1284> DW_AT_decl_line : 29
<2><1285>: Abbrev Number: 36 (DW_TAG_member)
<1286> DW_AT_name: ch
<1289> DW_AT_decl_file : 35
<128a> DW_AT_decl_line : 30
<128b> DW_AT_type:
<2><128f>: Abbrev Number: 36 (DW_TAG_member)
<1290> DW_AT_name: iVal
<1295> DW_AT_decl_file : 35
<1296> DW_AT_decl_line : 31
<1297> DW_AT_type:
<2><129b>: Abbrev Number: 36 (DW_TAG_member)
<129c> DW_AT_name: IVal
<12a1> DW_AT_decl_file : 35
<12a2> DW_AT_decl_line : 32
<12a3> DW_AT_type:
Notice that the union name has been changed to "$_4" in DIE <1279>.
The GNU 3.4.4 compiler generates the following DWARF data from the same source
code:
<1><11d0>: Abbrev Number: 27 (DW_TAG_union_type)
DW_AT_sibling : <123f>
DW_AT_name: (indirect string, offset: 0x6e): BASE_UNION
DW_AT_byte_size : 4
DW_AT_decl_file : 3
DW_AT_decl_line : 29
<2><11dc>: Abbrev Number: 28 (DW_TAG_member)
DW_AT_name: ch
DW_AT_decl_file : 3
DW_AT_decl_line : 30
DW_AT_type:
<2><11e6>: Abbrev Number: 28 (DW_TAG_member)
DW_AT_name: iVal
DW_AT_decl_file : 3
DW_AT_decl_line : 31
DW_AT_type:
<2><11f2>: Abbrev Number: 28 (DW_TAG_member)
DW_AT_name: IVal
DW_AT_decl_file : 3
DW_AT_decl_line : 32
DW_AT_type:
<2><11fe>: Abbrev Number: 29 (DW_TAG_subprogram)
DW_AT_sibling : <1219>
DW_AT_name: (indirect string, offset: 0x79): operator=
DW_AT_type: <123f>
DW_AT_artificial : 1
DW_AT_declaration : 1
<3><120d>: Abbrev Number: 9 (DW_TAG_formal_parameter)
DW_AT_type: <1245>
DW_AT_artificial : 1
<3><1213>: Abbrev Number: 10 (DW_TAG_formal_parameter)
DW_AT_type: <124b>
<2><1219>: Abbrev Number: 30 (DW_TAG_subprogram)
DW_AT_sibling : <1230>
DW_AT_name: $_4
DW_AT_artificial : 1
DW_AT_declaration : 1
<3><1224>: Abbrev Number: 9 (DW_TAG_formal_parameter)
DW_AT_type: <1245>
DW_AT_artificial : 1
<3><122a>: Abbrev Number: 10 (DW_TAG_formal_parameter)
DW_AT_type: <124b>
<2><1230>: Abbrev Number: 31 (DW_TAG_subprogram)
DW_AT_name: $_4
DW_AT_artificial : 1
DW_AT_declaration : 1
<3><1237>: Abbrev Number: 9 (DW_TAG_formal_parameter)
DW_AT_type: <1245>
DW_AT_artificial : 1
Notice that DIE <11D0> contains the correct type name. Also notice that
coincidently, DIE <1230> has a constructor with the "$_4" name which was used
as the type name in GNU 4.1.2.
Why is GNU 4.1.2 generating the mangled type name and how do I correct this to
generate the real type name?
