README.txt
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