This removes the need to clean anything up, avoids the issue of the file
changing from under us after we've indexed it, and simplifies offset
handling in a few places.
The parser is minimal and kinda jank, but it works. With a real parser
this could be extended to do pointer dereferencing, array subscripting,
and casting.
The lldwarf/drgn.dwarf split wasn't working out too well, and moving all
of drgn.dwarf into lldwarf (by rewriting it into C) would be way too
much work. Instead, use Cython, which results in a parser which is just
as fast but with much cleaner code overall. It also turns out lldwarf
wasn't doing GC right, so the switch also fixed that.
Resolving parameters, variables with function scope, and global
variables should work. This is just the variable resolution, no fetching
yet, but a bunch of refactors snuck in here so committing it all now.
The parsing library shouldn't really care about keeping track of these.
Instead, add __dict__ and getattr()/setattr() to all of the lldwarf
objects so higher layers can store the offset if they want.
DwarfDie is special in two ways:
1. We want to store an offset for the DIE so we know where to parse
sibling and children entries.
2. For some attributes, we need to store an offset so we know where to
find them later.
Both of these are changed to be relative to the CU rather than the
buffer.
I wrote all of this code a few months back and am just now getting
around to committing it. The low-level DWARF parsing library is pretty
solid, although it only implements a subset of DWARF so far. The CLI and
higher-level interface are experimental.
