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Re: Support constants for DW_AT_data_member_location
- From: Jim Blandy <jimb at codesourcery dot com>
- To: Vladimir Prus <vladimir at codesourcery dot com>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Thu, 29 Nov 2007 11:38:37 -0800
- Subject: Re: Support constants for DW_AT_data_member_location
- References: <200711291254.14423.vladimir@codesourcery.com>
Vladimir Prus <vladimir at codesourcery.com> writes:
> DWARF standard allows DW_AT_data_member_location value
> to be a plain constant, but GDB does not. Is the following OK?
A constant can have other FORMs, too; how about this?
gdb/ChangeLog:
2007-11-29 Jim Blandy <jimb@codesourcery.com>
* dwarf2read.c (dwarf2_attr_is_constant): New function.
(dwarf2_add_field): Use it to recognize DW_AT_data_member_location
attributes with constant values; use
dwarf2_get_attr_constant_value to get said values.
diff -r c4f654de59cf gdb/dwarf2read.c
--- a/gdb/dwarf2read.c Thu Nov 29 11:28:59 2007 -0800
+++ b/gdb/dwarf2read.c Thu Nov 29 11:33:57 2007 -0800
@@ -1012,6 +1012,8 @@ static void store_in_ref_table (unsigned
static unsigned int dwarf2_get_ref_die_offset (struct attribute *,
struct dwarf2_cu *);
+
+static int dwarf2_attr_is_constant (struct attribute *);
static int dwarf2_get_attr_constant_value (struct attribute *, int);
@@ -3380,8 +3382,11 @@ dwarf2_add_field (struct field_info *fip
attr = dwarf2_attr (die, DW_AT_data_member_location, cu);
if (attr)
{
- FIELD_BITPOS (*fp) =
- decode_locdesc (DW_BLOCK (attr), cu) * bits_per_byte;
+ if (dwarf2_attr_is_constant (attr))
+ FIELD_BITPOS (*fp) = dwarf2_get_attr_constant_value (attr, 0);
+ else
+ FIELD_BITPOS (*fp) =
+ decode_locdesc (DW_BLOCK (attr), cu) * bits_per_byte;
}
else
FIELD_BITPOS (*fp) = 0;
@@ -9008,6 +9013,26 @@ dwarf2_get_ref_die_offset (struct attrib
return result;
}
+/* Return non-zero if ATTR's value falls in the 'constant' class, or
+ zero otherwise. When this function returns true, you can apply
+ dwarf2_get_attr_constant_value to it. */
+static int
+dwarf2_attr_is_constant (struct attribute *attr)
+{
+ switch (attr->form)
+ {
+ case DW_FORM_sdata:
+ case DW_FORM_udata:
+ case DW_FORM_data1:
+ case DW_FORM_data2:
+ case DW_FORM_data4:
+ case DW_FORM_data8:
+ return 1;
+ default:
+ return 0;
+ }
+}
+
/* Return the constant value held by the given attribute. Return -1
if the value held by the attribute is not constant. */