Re: [rfc/cp] method stub assertions

David Carlton
2004-01-06T18:41:52Z

On Tue, 6 Jan 2004 12:05:23 -0500, Daniel Jacobowitz <drow@mvista.com> said:

> The debug information for A::bad6 does not specify that it is a
> method. Rather only the debug info for class A specifies that it
> has a method named A::bad6.

I'm coming into this discussion late (without closely reading all of
it, no less), so I may be missing something, but I wouldn't phrase
things this way. I've compiled the following file (g++ -g -S -dA)

class C {
public:
int foo();
};

int C::foo() {
return 1;
}

and get, among other things, this output:

# Start of debug info for C.

.uleb128 0x2 # (DIE (0x25) DW_TAG_structure_type)
.long 0x8f # DW_AT_sibling
.ascii "C\0" # DW_AT_name
.byte 0x1 # DW_AT_byte_size
.byte 0x1 # DW_AT_decl_file
.byte 0x1 # DW_AT_decl_line
...

# Debug info for declaration for C::foo.

.uleb128 0x7 # (DIE (0x76) DW_TAG_subprogram)
.byte 0x1 # DW_AT_external
.ascii "foo\0" # DW_AT_name
.byte 0x1 # DW_AT_decl_file
.byte 0x3 # DW_AT_decl_line
.long .LC6 # DW_AT_MIPS_linkage_name: "_ZN1C3fooEv"
.long 0xa6 # DW_AT_type
.byte 0x1 # DW_AT_declaration

...

# Done with debug info for C.

.byte 0x0 # end of children of DIE 0x25

...

# Start of debug info for definition of C::foo.

.uleb128 0xc # (DIE (0xad) DW_TAG_subprogram)
.long 0xcf # DW_AT_sibling
.long 0x76 # DW_AT_specification

That DW_AT_specification in the definition of C::foo refers to DIE
0x76, which is the declaration for C::foo. And the declaration for
C::foo is nested within the die for C. So if we're reading the
definition for C::foo, it wouldn't be hard at all to find out that the
DW_TAG_subprogram in question is in fact a method of a class instead
of a free function: follow the specification, and look at its parent
DIE. (It would have been hard a few months ago, but it's not hard
now. :-) )

David Carlton
carlton@kealia.com