[fpc-devel] AnsiString in DWARF2 vs DWARF3

[Graeme Geldenhuys]

Hi,

Recently I mentioned a issue with debugging (using GDB) and indexing
in a AnsiString to retrieve a specific character from that string.

DWARF2
-----------
eg:
  S := 'mystring';
GDB can display the value of S without problems because it is treated
as a PChar (from what I can see and understand).

  c := s[1]
GDB displays the wrong character from the string. GDB displays the 'y'
character instead of the 'm' character. GDB or DWARF2 treats a
AnsiString (or an array of char) being 0-indexing instead of
1-indexed.


DWARF3
-----------
   c := s[1]
GDB correctly displays the first character of the string stored in s.
This is accomplished by using tho lower_bound = 1 attribute in DWARF3.

  s := 'mystring'
GDB cannot display the value of the ansistring stored in s, even thou
DW_AT_type is set as well. It seems GDB cannot figure out how to
handle displaying s, even though it knows it's an character array.


It seems the DWARF2/3 support with GDB is playing the vice-versa game.
Fix one, break one.


This last part in DWARF3 above... it seems FPC has fulfilled the specs
for DWARF3 (again from what I can understand from the DWARF3 spec
inself) by correctly describing a AnsiString, so what is the issue now
- why can't GDB display the value (full string value) of a ansistring
variable? Is it now the lack of Object Pascal support in GDB giving us
the problems?


Sorry if this sounds dumb, but I'm new to DWARF and debuggers, so I
just want to try and get my bearings with where exactly the problem
sits. Is it with FPC, or with GDB, or both.

-- 
Regards,
  - Graeme -


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