[RFC] dwarf2_read_address(): sign extend as appropriate

Kevin Buettner
2007-04-20T23:33:18Z

Any comments regarding the patch below?

I wrote it last summer, so my memory about it is rather hazy aside
from the fact that it fixed a bunch of C++ frame base problems on
mips64 targets.

It shouldn't affect any architecture other than mips because mips is
the only one which defines an integer_to_address method. It also
addresses Andrew's FIXME comment from nearly four years ago...

* dwarf2expr.c (unsigned_address_type): Add forward declaration.
(dwarf2_read_address): Sign extend return address as required by
target architecture.

Index: dwarf2expr.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2expr.c,v
retrieving revision 1.19
diff -u -p -r1.19 dwarf2expr.c
--- dwarf2expr.c 9 Jan 2007 17:58:50 -0000 1.19
+++ dwarf2expr.c 20 Apr 2007 23:23:50 -0000
@@ -33,6 +33,7 @@

static void execute_stack_op (struct dwarf_expr_context *,
gdb_byte *, gdb_byte *);
+static struct type * unsigned_address_type (void);

/* Create a new context for the expression evaluator. */

@@ -205,9 +206,24 @@ dwarf2_read_address (gdb_byte *buf, gdb_
error (_("dwarf2_read_address: Corrupted DWARF expression."));

*bytes_read = TARGET_ADDR_BIT / TARGET_CHAR_BIT;
- /* NOTE: cagney/2003-05-22: This extract is assuming that a DWARF 2
- address is always unsigned. That may or may not be true. */
- result = extract_unsigned_integer (buf, TARGET_ADDR_BIT / TARGET_CHAR_BIT);
+
+ /* Some architectures (such as MIPS) use signed addresses. Those that
+ do will have registered a gdbarch_integer_to_address method. Use
+ that method if it exists, otherwise fall back to extracting an
+ unsigned integer as the address.
+
+ Note: kevinb/2006-07-10: The use of `unsigned_address_type' in
+ the gdbarch_integer_to_address() call below refers to the type of
+ `buf' and has no bearing on the signedness of the address being
+ returned. In all of the integer-to-address conversion methods
+ being used by GDB at the time that this comment was written, this
+ type was used only to determine the size of `buf'. */
+ if (gdbarch_integer_to_address_p (current_gdbarch))
+ result = gdbarch_integer_to_address (current_gdbarch,
+ unsigned_address_type(), buf);
+ else
+ result = extract_unsigned_integer (buf,
+ TARGET_ADDR_BIT / TARGET_CHAR_BIT);
return result;
}