
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.  On 18 Sep 14
the STABS support was completely removed. The new structure looks like this:

                  debuginfo.c 
  
                   readelf.c

                  readdwarf.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 parses 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 for debug info.  All straightforward.

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

There are 2 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

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

Originally there was also goal (3) Simplify the stabs reader.
But stabs support was broken since 3.9.0 and completely removed in 3.10.0.

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. Old versions
of the stabs type reader can be found in the subversion repository
as m_debuginfo/UNUSED_STABS.txt, the stabs line-number reader was in
m_debuginfo/readstabs.c. The old version of this file explained more
about the setup.

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.