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Re: RFC: fix another regression w/ gcc svn trunk
>>>>> "Joel" == Joel Brobecker <brobecker@adacore.com> writes:
Joel> This looks reasonable to me. For 7.2, I'm also 50/50, so I propose
Joel> the following compromise: Since it is mostly affecting an unreleased
Joel> version of GCC, we can leave this out of 7.2, and reconsider for 7.2.1
Joel> after an observation period on the head?
Sounds reasonable to me.
>> +/* Given an attr with a DW_FORM_dataN value in host byte order,
>> + zero-extend it as appropriate for the symbol's type. */
Joel> I think it would be nice to explain in the comment the reason for
Joel> zero-extending as opposed to sign-extending?
Good idea. I have appended what I am checking in.
Tom
2010-07-27 Tom Tromey <tromey@redhat.com>
* dwarf2read.c (dwarf2_const_value_data): Never sign extend.
Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.430
diff -u -r1.430 dwarf2read.c
--- dwarf2read.c 28 Jul 2010 16:23:58 -0000 1.430
+++ dwarf2read.c 28 Jul 2010 19:58:30 -0000
@@ -10446,8 +10446,13 @@
}
-/* Given an attr with a DW_FORM_dataN value in host byte order, sign-
- or zero-extend it as appropriate for the symbol's type. */
+/* Given an attr with a DW_FORM_dataN value in host byte order,
+ zero-extend it as appropriate for the symbol's type. The DWARF
+ standard (v4) is not entirely clear about the meaning of using
+ DW_FORM_dataN for a constant with a signed type, where the type is
+ wider than the data. The conclusion of a discussion on the DWARF
+ list was that this is unspecified. We choose to always zero-extend
+ because that is the interpretation long in use by GCC. */
static void
dwarf2_const_value_data (struct attribute *attr,
struct symbol *sym,
@@ -10456,12 +10461,7 @@
LONGEST l = DW_UNSND (attr);
if (bits < sizeof (l) * 8)
- {
- if (TYPE_UNSIGNED (SYMBOL_TYPE (sym)))
- l &= ((LONGEST) 1 << bits) - 1;
- else
- l = (l << (sizeof (l) * 8 - bits)) >> (sizeof (l) * 8 - bits);
- }
+ l &= ((LONGEST) 1 << bits) - 1;
SYMBOL_VALUE (sym) = l;
SYMBOL_CLASS (sym) = LOC_CONST;