From: dje@google.com (Doug Evans)
To: gdb-patches@sourceware.org
Subject: patch for 7.2.1? dwarf2read.c (dwarf2_const_value_data): Never sign extend.
Date: Sat, 13 Nov 2010 02:15:00 -0000 [thread overview]
Message-ID: <20101113021516.43ECE2461B0@ruffy.mtv.corp.google.com> (raw)
This is rather nasty.
class test
{
static const int k128 = 128;
};
test foo;
int
main ()
{
return 0;
}
$ gdb a.out
(gdb) start
(gdb) p test::k128
-128
I propose adding this patch to the 7.2.1 branch.
[I haven't run a regression test.
If there are changes needed I'll check for those before checking in.]
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 1.431
retrieving revision 1.432
diff -u -p -r1.431 -r1.432
--- dwarf2read.c 28 Jul 2010 19:04:07 -0000 1.431
+++ dwarf2read.c 28 Jul 2010 20:05:03 -0000 1.432
@@ -10485,8 +10485,13 @@ dwarf2_const_value (struct attribute *at
}
-/* 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,
@@ -10495,12 +10500,7 @@ dwarf2_const_value_data (struct attribut
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;
next reply other threads:[~2010-11-13 2:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-13 2:15 Doug Evans [this message]
2010-11-20 5:25 ` Joel Brobecker
2010-11-25 19:43 ` Doug Evans
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