Re: 8-byte register values on a 32-bit machine

Joel Brobecker
2003-03-01T20:33:20Z

> Yup, that's defenitely what it does for stabs, and from looking at the
> code, it does it for other debug formats as well (including dwarf-2).
> Right now, GDB interprets this as that the variable is stored in
> consecutive registers starting at the register number indicated by the
> debug info. I have a strong suspicion that there are several GDB
> targets that rely on this behaviour. However, it isn't working for
> the i386 since GCC allocates the registers in an order that's
> different from the order that GDB uses.

What I have seen as well is GCC an 8 bytes structure over 2 registers
(2 fields of 4 bytes, one field on each register). The first register
used (and specified in the stabs info) was %ebx, and the next one was
sort of consecutive. It was %esi. The only thing is that there are two
special registers in the middle (%esp, and %ebp) :-).

Because of this, even if we modified GCC to allocate the registers in
the same order as the GDB order (or modify the GDB order, if that's
possible), we'll still have situations where this is not going to work.

I think we've lost the stabs battle. So I started to look into the
DWARF2 format, but could not find anything that helps. Does anybody know
if this format supports this sort of situation?

--
Joel