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      1 
      2 On 4 Apr 06, the debuginfo reader (m_debuginfo) was majorly cleaned up
      3 and restructured.  It has been a bit of a tangle for a while.  The new
      4 structure looks like this:
      5 
      6                   debuginfo.c 
      7   
      8                    readelf.c
      9 
     10         readdwarf.c        readstabs.c
     11 
     12                    storage.c
     13 
     14 Each .c can only call those below it on the page.
     15 
     16 storage.c contains the SegInfo structure and stuff for 
     17 maintaining/searching arrays of symbols, line-numbers, and Dwarf CF 
     18 info records.
     19 
     20 readdwarf.c and readstabs.c parse the relevant kind of info and 
     21 call storage.c to store the results.
     22 
     23 readelf.c reads ELF format, hands syms directly to storage.c,
     24 then delegates to readdwarf.c/readstabs.c for debug info.  All 
     25 straightforward.
     26 
     27 debuginfo.c is the top-level file, and is quite small.
     28 
     29 There are 3 goals to this:
     30 
     31 (1) Generally tidy up something which needs tidying up
     32 
     33 (2) Introduce more modularity, so as to make it easier to add
     34     readers for other formats, if needed
     35 
     36 (3) Simplify the stabs reader.
     37 
     38 Rationale for (1) and (2) are obvious.
     39 
     40 Re (3), the stabs reader has for a good year contained a sophisticated
     41 and impressive parser for stabs strings, with the aim of recording in 
     42 detail the types of variables (I think) (Jeremy's work).  Unfortunately 
     43 that has caused various segfaults reading stabs info in the past few months
     44 (#77869, #117936, #119914, #120345 and another to do with deeply nested
     45 template types).
     46 
     47 The worst thing is that it is the stabs type reader that is crashing,
     48 not the stabs line-number reader, but the type info is only used by
     49 Helgrind, which is looking pretty dead at the moment.  So I have lifed
     50 out the type-reader code and put it in UNUSED_STABS.txt for safe
     51 storage, just leaving the line-number reader in place.
     52 
     53 If Helgrind ever does come back to life we will need to reinstate the
     54 type storage/reader stuff but with DWARF as its primary target.
     55 Placing the existing stabs type-reader in hibernation improves
     56 stability whilst retaining the development effort/expertise that went
     57 into it for possible future reinstatement.
     58