Re: PATCH: new DWARF-2 reader

[Daniel Berlin <dberlin at dberlin dot org>]

This won't thread properly, sorry (i'm not on the list, so this is a
paste from the web archives)

> >>>>> "Casey" == Casey Marshall <csm@gnu.org> writes:
> 
> Revised again, fixing a few remaining problems with the implementation
> (the DWARF-2 spec is really hard to interpret! I hope now that it is
> accurate) and fit it into the Throwable machinery.
> 
> 
You should look at the DWARF-3 spec on dwarf.freestandards.org
A lot of stuff has been clarified.
On that note:

> +
> +    private void get (ByteBuffer b)
> +    {
> +      total_length = (long) b.getInt () & 0xFFFFFFFFL;
> 
	If total_length == 0xfffffff, 
then the offset size is 8 (IE it's a 64 bit value)

This is how dwarf-3 differentiates between 32 bit and 64 bit sections.

This is *actually used* in practice, so it shoudl be handled.

> +      version = b.getShort () & 0xFFFF;
> +      prologue_length = (long) b.getInt () & 0xFFFFFFFFL;

^^^^^^^^^^^^^^
This field is offset_size bytes

> +      minimum_instruction_length = b.get () & 0xFF;
> +      default_is_stmt = b.get () != 0;
> +      line_base = b.get ();
> +      line_range = b.get () & 0xFF;
> +      opcode_base = b.get () & 0xFF;
> +      b.get (standard_opcode_lengths);
> +    }
> +
> +        if (header.version != 2 || header.opcode_base != 10)
> 

version == 3 is in use now as well.

Why not support opcode_base other than 10 as well?
It's just a little more code for standard opcode lengths.

> +        final int const_pc_add = 245 / header.line_range;
> 

It's actually ((255 - opcode_base) / (line_range) * min_insn_length)

>