Re: [PATCH] libdw: Add new function dwarf_getlocations.

[Mark Wielaard <mjw at redhat dot com>]

On Wed, 2013-09-04 at 16:42 +0200, Jan Kratochvil wrote:
> On Wed, 04 Sep 2013 16:30:19 +0200, Mark Wielaard wrote:
> > Good point, I missed that. It is always good to do less work if at all
> > possible. I implemented it slightly differently from your suggestion,
> > but I believe it addresses your point. See new patch attached.
> 
> This makes address == 0 a special case.
> 
> I do not have an overview how elfutils handles that but at least GDB tries to
> handle address 0 as general valid address as it is a normal code location on
> many embedded targets.  (Although for example GNU/Linux-targeted code does not
> handle address 0 correctly as it is not much a problem for GNU/Linux targets.)

We can use -1. Which should never match. I'll test the same patch with:

diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
index cb4b483..c9df8f4 100644
--- a/libdw/dwarf_getlocation.c
+++ b/libdw/dwarf_getlocation.c
@@ -678,8 +678,8 @@ getlocations_addr (attr, offset, basep, startp, endp, address,
   *startp = *basep + begin;
   *endp = *basep + end;
 
-  /* If address is zero we want them all, otherwise only those that match.  */
-  if (address != 0 && (address < *endp || address >= *startp))
+  /* If address is minus one we want them all, otherwise only matching.  */
+  if (address != (Dwarf_Word) -1 && (address < *endp || address >= *startp))
     goto next;
 
   if (getlocation (attr->cu, &block, expr, exprlen, IDX_debug_loc) != 0)
@@ -828,6 +828,6 @@ dwarf_getlocations (attr, offset, basep, startp, endp, expr, exprlen)
       return -1;
     }
 
-  return getlocations_addr (attr, offset, basep, startp, endp, 0, d,
-                           expr, exprlen);
+  return getlocations_addr (attr, offset, basep, startp, endp,
+                           (Dwarf_Word) -1, d, expr, exprlen);
 }

Thanks,

Mark