From: Doug Evans <dje@google.com>
Date: Thu, 25 Nov 2010 19:42:31 +0000 (+0000)
Subject: 	* dwarf2read.c (dwarf2_const_value_data): Never sign extend.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f9e7c18860a34cb99f116a0d702009470e63bc33;p=thirdparty%2Fbinutils-gdb.git

	* dwarf2read.c (dwarf2_const_value_data): Never sign extend.
---

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 93a1853f735..05a4fca83be 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2010-11-25  Tom Tromey  <tromey@redhat.com>
+
+	* dwarf2read.c (dwarf2_const_value_data): Never sign extend.
+
 2010-11-18  Phil Muldoon  <pmuldoon@redhat.com>
 
     	PR mi/11407
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 1e752357e00..55b3f082877 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -9165,8 +9165,13 @@ dwarf2_const_value (struct attribute *attr, struct symbol *sym,
 }
 
 
-/* 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,
@@ -9175,12 +9180,7 @@ dwarf2_const_value_data (struct attribute *attr,
   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;