Dejan Jevtic 6cb9b78f0d mips32/64: According to DWARF version 4 in DW_TAG_structure_type we can
have DW_AT_signature attribute. That wasn't the case in DWARF version 3.

From DWARF version 4:
If the complete declaration of a type has been placed in a separate type unit, 
an incomplete declaration of that type in the compilation unit may provide the
unique 64-bit signature of the type using a DW_AT_signature attribute.

This patch adds an extra field in TyStOrUn structure (typeR). This field is 
reference to other TyEnt that is placed in separate type unit. Because of the new
field in TyStOrUn structure we need to add an extra case in parse_type_DIE
that will put the right reference to other TyEnt and an extra case in
ML_(describe_type) that will describe type when the ty->Te.TyStOrUn.typeR field
is used.

This patch is resolving the problem with memcheck/tests/dw4 test when it's 
compiled with compiler that will emit DW_AT_signature under the DW_TAG_structure_type.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13891
2014-04-04 10:20:03 +00:00
..

On 4 Apr 06, the debuginfo reader (m_debuginfo) was majorly cleaned up
and restructured.  It has been a bit of a tangle for a while.  The new
structure looks like this:

                  debuginfo.c 
  
                   readelf.c

        readdwarf.c        readstabs.c

                   storage.c

Each .c can only call those below it on the page.

storage.c contains the SegInfo structure and stuff for 
maintaining/searching arrays of symbols, line-numbers, and Dwarf CF 
info records.

readdwarf.c and readstabs.c parse the relevant kind of info and 
call storage.c to store the results.

readelf.c reads ELF format, hands syms directly to storage.c,
then delegates to readdwarf.c/readstabs.c for debug info.  All 
straightforward.

debuginfo.c is the top-level file, and is quite small.

There are 3 goals to this:

(1) Generally tidy up something which needs tidying up

(2) Introduce more modularity, so as to make it easier to add
    readers for other formats, if needed

(3) Simplify the stabs reader.

Rationale for (1) and (2) are obvious.

Re (3), the stabs reader has for a good year contained a sophisticated
and impressive parser for stabs strings, with the aim of recording in 
detail the types of variables (I think) (Jeremy's work).  Unfortunately 
that has caused various segfaults reading stabs info in the past few months
(#77869, #117936, #119914, #120345 and another to do with deeply nested
template types).

The worst thing is that it is the stabs type reader that is crashing,
not the stabs line-number reader, but the type info is only used by
Helgrind, which is looking pretty dead at the moment.  So I have lifed
out the type-reader code and put it in UNUSED_STABS.txt for safe
storage, just leaving the line-number reader in place.

If Helgrind ever does come back to life we will need to reinstate the
type storage/reader stuff but with DWARF as its primary target.
Placing the existing stabs type-reader in hibernation improves
stability whilst retaining the development effort/expertise that went
into it for possible future reinstatement.