More on DWARF2

[Daniel Berlin <dan at cgsoftware dot com>]

Oh, and you can't simply call read_comp_unit because it knows the hash
tables need to be emptied, and trashes them.  That's why i mentioned
about the different abbrev tables, etc. 
So your die reference list would be broken, etc. There is also no list
of die's to extend, we don't pass one around. Any communication
between routines, except recently (Kevin's changes to pass around a cu
header in some cases), is done through global variables.
We also destroy the temp obstack at the end of reading the CU, which
destroys the DIE list.
You're proposing something that is about 75% of the work of what i've
done.  
However, it requires *more* memory than we currently use, because it
would mean retaining more info, with no real way to distinguish the
lifetimes of the info.
I actually started by doing that, and then noticed we might as well
just modularize it the whole way, and keep all the info about a given
compilation unit, in a structure for that compilation unit, so we
could throw it out when that compilation unit was done.
You are proposing something that still keeps around the global
variables, etc.
It's the difference between 2 months, and 2 and a half months, of
coding.  I figured since the original design had come back
to bite us in the ass, I might as well do what I could to prevent it
from happening again, and if it did happen, to make it so pieces could
be reused without so much pain and suffering.

The changes you propose will touch about the same amount of code I
touched, in reality, as well. Fully modularizing it from 75% of the
way there removes more code than it adds (It removed 30k from the
diff), so you might actually touch *more* code.

If you wanted to try it, you can take my patches (or I can give you an
older diff where i had gone this way), and you can see it's going to
require about the same amount of work.  You'll have to touch just
about every procedure either way.
Unless, of course, you start introducing more global variables to
communicate state, which IMHO, is a bad idea.

--Dan
-- 
"He asked me if I knew what time it was.  I said, "Yes, but not
right now."
"-Steven Wright