ret value of bfd_get_sign_extend_vma

[Michael Mueller]

Can someone explain to me what the return value of function 
bfd_get_sign_extend_vma means? What the docu says is a mystery to me:

"Indicates if the target architecture "naturally" sign extends an 
address. Some architectures implicitly sign extend address values when 
they are converted to types larger than the size of an address. For 
instance, bfd_get_start_address() will return an address sign extended 
to fill a bfd_vma when this is the case."

How can an address have a sign? I think of an address as an unsigned 
quantity.

I found 2 uses of bfd_get_sign_extend_vma in gdb (I'm talking of solaris 
sparc 32 and 64 bit):

1) In dbxread.c, macro INTERNALIZE_SYMBOL

There it's used (among others) to read a negative offset of a local 
variable to the frame pointer. This should be sign extended.
See http://sources.redhat.com/ml/gdb-patches/2004-06/msg00433.html
and http://sources.redhat.com/ml/gdb/2001-08/msg00078.html

2) In dwarfread2.c

There it's used to read addresses which have no sign.