Re: [RFA 2/4] dwarf2_physname

Keith Seitz
2010-02-02T23:23:56Z

On 02/01/2010 02:19 PM, Daniel Jacobowitz wrote:

> What're we trying to answer? For instance, is it the distinction
> between local variables and global variables? This is interesting
> because I believe that function-local classes get the enclosing
> function as a prefix, but obviously function-local automatic variables
> should not.

Yes, it was specifically to deal with class static members. Reminder:

namespace
{
namespace G
{
int Gx;
};
};

gcc will output:
DW_TAG_namespace
-- DW_TAG_namespace
-- DW_AT_name = "G"
---- DW_TAG_variable
---- DW_AT_name = "Gx"

DW_TAG_variable
-- DW_AT_location
-- DW_AT_specification = DW_TAG_variable above

This seems to be correct as far as my interpretation of the DWARF3 spec
(Dec 20, 2005), Section 4.1 #6 (pg 60).

> I'm not sure how DW_TAG_member comes into this either, that doesn't
> entirely make sense for non-static class members. Be careful about
> this one: GCC sometimes incorrectly uses DW_TAG_variable, when the
> DWARF standard says they should be DW_TAG_member.

DW_TAG_member does not run through this branch, unless, as you say, gcc
incorrectly emits DW_TAG_variable instead of DW_TAG_member. I have only
seen gcc output DW_TAG_variable for member data in two situations: 1)
static class members (which I think is correct) and 2) const class
members where the class is not instantiated.

To elaborate on #2:

Consider the following class:

class A
{
public:
static const int a_constant = 3;
};

int
main (int argc, char* argv[])
{
return A::a_constant;
}

Gcc will *NOT* output anything about A::a_constant *except* for a
DW_TAG_variable describing it (DW_AT_name = "a_constant"). No
DW_AT_specification (as I think there should be). In fact,
DW_TAG_class_type for A is completely omitted. The only clue that gdb
gets (either dwarf2_physname or CVS HEAD) is in DW_AT_MIPS_linkage_name.
This is obviously a gcc bug.

Do you have another example where gcc does this that you'd like me to
look at?

Or maybe I'm simply not answering your question? [A kind of forest/tree
thing...]

Keith