Removing TYPE_VPTR_FIELDNO uses (was: Re: [patch ping] Set TYPE_VPTR_BASETYPE/TYPE_VPTR_FIELDNO of XL C++ virtual class)

[Daniel Jacobowitz <drow@false.org>]

On Thu, Sep 29, 2005 at 12:53:18AM -0400, Wu Zhou wrote:
> - gnu-v2-abi.c is for an old ABI.  Not relevant.
> - stabsread.c is for a different debug format.  Not relevant.
> - dwarf2read.c: to read out data for VPTRs if there are any. No need for
> any change IMO.

Yes, I agree.

> - gdbtypes.c/gdbtype.h: to initialize VPTR_FIELDNO (in alloc_type and
> create_array_type), fill VPTRs (in fill_in_vptr_fieldno), and dump VPTRs
> (in recursive_dump_type).  Maybe some change to the type dumping is
> needed.

Not if we leave them for older ABIs and stabs.

> - varobj.c (cplus_class_num_children and cplus_name_of_child): The code
> will ignore VPTRs when iterating thru the base classes.  I don't know
> the way how to iterate thru the base classes if there is no dependence
> for VPTRs.  Maybe we need to find a way for that?

For this code, it may suffice to ignore DW_AT_artificial fields and
make sure that the vptr is tagged as artificial.  Or, call a new C++
ABI method (cp-abi.h) to check for vptrs and ignore them.

> - eval.c (evaluate_subexp_standard): TYPE_VPTR_BASETYPE is used to iterate
> the baseclasses to find the real address of the virtual function.

This code needs to be (A) read and thought about, so that we can figure
out what it used to do, and (B) replaced with something less broken. 
It hasn't worked in forever.  Take a look at what METHOD_PTR_IS_VIRTUAL
expands to!

I believe this was specific to one particular C++ ABI.  I don't
remember which... maybe gnuv2, maybe HP aCC.

> - gnu-v3-abi.c: VPTRs is used for rtti, virtual function and virtual base 
> class offset.

In this file, I think we can skip all the rigamarole with debug
information to find the vptr.  It's very easy: it's the size of a
pointer, and it's at offset 0.  Always.

Unless of course there isn't one.  We may need to figure out what the
field at offset 0 is to see whether it's a vptr or a user variable.  I
haven't thought about that in a while; maybe we can assume that there
is one by the time we get into this file.

-- 
Daniel Jacobowitz
CodeSourcery, LLC