Re: [RFC] Dont skip DW_TAG_member in load_partial_dies()

[Daniel Jacobowitz <drow@false.org>]

On Tue, Feb 15, 2005 at 03:06:57PM -0600, Manoj Iyer wrote:
> 
> GDB prints internal error with C++ application produced by XLC.

Many of the tests in the GDB testsuite already will probably produce
this error, if you want to try running the testsuite with xlC.  It
probably won't be easy, though.

I'm copying this to Elena, since she is the maintainer of the DWARF-2
reader.  Your patch looks right to me.  In fact, I've been working on
running the GDB testsuite using ARM's compiler today, and I have a
patch that looks exactly like this in my working directory :-)

> When the above testcase is compiled -m64 by XLC, GDB generates an internal
> error:
> 
> "internal-error: could not find partial DIE in cache"
> 
> GCC creates a DWARF TAG for "a" as DW_TAG_variable and XLC creates
> DW_TAG_member. GDB throws away TAGS that it find as uninteresting. In this
> case DW_TAG_member. (this is in dwarf2read.c function:
> load_partial_dies(). )
> 
> GCC created DWARF information
> -------------------------------
>  <2><102>: Abbrev Number: 13 (DW_TAG_variable)
>      DW_AT_name        : a
>      DW_AT_decl_file   : 1
>      DW_AT_decl_line   : 13
>      DW_AT_MIPS_linkage_name: _ZN1XIiE1aE
>      DW_AT_type        : <d5>
>      DW_AT_external    : 1
>      DW_AT_declaration : 1
> 
> XLC created DWARF information
> ------------------------------
>  <2><96>: Abbrev Number: 5 (DW_TAG_member)
>      DW_AT_name        : a
>      DW_AT_accessibility: 1     (public)
>      DW_AT_declaration : 1
>      DW_AT_type        : <78>
> 
> 
> GCC in this case is producing wrong information. According to DWARF
> spec:
> 
> " If the variable entry represents the defining declaration for a C++
> static data member of a structure, class or union, the entry has a
> DW_AT_specification attribute, whose value is a reference to the debugging
> information entry representing the declaration of this data member. The
> referenced entry has the tag DW_TAG_member and will be a child of some
> class, structure or union type entry. "
> 
> So I think GDB needs to handle the DW_TAG_member and not skip it, when
> dealing with  C++.
> 
> Here is a patch to GDB that will fix this problem
> 
> ================ Patch to gdb ==================
> 2005-02-15  Manoj Iyer  <manjo@austin.ibm.com>
> 
>         * dwarf2read.c (load_partial_dies): Save DIE with tag
>         DW_TAG_member, generated by XLC when compiling C++ application.
> 
> diff -Naur ./old/src/gdb/dwarf2read.c ./new/src/gdb/dwarf2read.c
> --- ./old/src/gdb/dwarf2read.c  2005-02-15 11:13:05.000000000 -0600
> +++ ./new/src/gdb/dwarf2read.c  2005-02-22 10:24:08.000000000 -0600
> @@ -5167,7 +5167,8 @@
>           && abbrev->tag != DW_TAG_enumerator
>           && abbrev->tag != DW_TAG_subprogram
>           && abbrev->tag != DW_TAG_variable
> -         && abbrev->tag != DW_TAG_namespace)
> +         && abbrev->tag != DW_TAG_namespace
> +         && abbrev->tag != DW_TAG_member)
>         {
>           /* Otherwise we skip to the next sibling, if any.  */
>           info_ptr = skip_one_die (info_ptr + bytes_read, abbrev, cu);
> 
> ========================= END PATCH ======================
> 
> 
> ok to commit?
> 
> Thanks
> -----
> manjo
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> + Cogito ergo sum                                                          +
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 

-- 
Daniel Jacobowitz
CodeSourcery, LLC