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[rfc] Recognize GCC pointer to member function DWARF2 descriptions
- From: Daniel Jacobowitz <drow at false dot org>
- To: gdb-patches at sourceware dot org
- Date: Sun, 6 Aug 2006 22:57:40 -0400
- Subject: [rfc] Recognize GCC pointer to member function DWARF2 descriptions
GCC emits DW_TAG_ptr_to_member_type for pointers to member data, but not
for pointers to member functions. I plan to fix this in GCC eventually,
but in the mean time, this does some pattern recognition on the GCC
output to convert it into a pointer to member. It recognizes structures
of the form:
struct {
void (*__pfn) (args, ...);
ptrdiff_t __delta;
};
Comments? This isn't beautiful, but I don't think it's unbearably
ugly, either.
--
Daniel Jacobowitz
CodeSourcery
2006-08-06 Daniel Jacobowitz <dan@codesourcery.com>
* dwarf2read.c (quirk_gcc_member_function_pointer): New.
(read_structure_type): Call it.
Index: src/gdb/dwarf2read.c
===================================================================
--- src.orig/gdb/dwarf2read.c 2006-08-05 10:10:11.000000000 -0400
+++ src/gdb/dwarf2read.c 2006-08-06 22:52:02.000000000 -0400
@@ -3708,6 +3708,69 @@ is_vtable_name (const char *name, struct
return 0;
}
+/* GCC outputs unnamed structures that are really pointers to member
+ functions, with the ABI-specified layout. If DIE (from CU) describes
+ such a structure, set its type, and return nonzero. Otherwise return
+ zero. */
+
+static int
+quirk_gcc_member_function_pointer (struct die_info *die, struct dwarf2_cu *cu)
+{
+ struct objfile *objfile = cu->objfile;
+ struct type *type;
+ struct die_info *pfn_die, *delta_die;
+ struct attribute *pfn_name, *delta_name;
+ struct type *pfn_type, *domain_type;
+
+ /* Check for a structure with no name and two children. */
+ if (die->tag != DW_TAG_structure_type
+ || dwarf2_attr (die, DW_AT_name, cu) != NULL
+ || die->child == NULL
+ || die->child->sibling == NULL
+ || (die->child->sibling->sibling != NULL
+ && die->child->sibling->sibling->tag != DW_TAG_padding))
+ return 0;
+
+ /* Check for __pfn and __delta members. */
+ pfn_die = die->child;
+ pfn_name = dwarf2_attr (pfn_die, DW_AT_name, cu);
+ if (pfn_die->tag != DW_TAG_member
+ || pfn_name == NULL
+ || DW_STRING (pfn_name) == NULL
+ || strcmp ("__pfn", DW_STRING (pfn_name)) != 0)
+ return 0;
+
+ delta_die = pfn_die->sibling;
+ delta_name = dwarf2_attr (delta_die, DW_AT_name, cu);
+ if (delta_die->tag != DW_TAG_member
+ || delta_name == NULL
+ || DW_STRING (delta_name) == NULL
+ || strcmp ("__delta", DW_STRING (delta_name)) != 0)
+ return 0;
+
+ /* Find the type of the method. */
+ pfn_type = die_type (pfn_die, cu);
+ if (pfn_type == NULL
+ || TYPE_CODE (pfn_type) != TYPE_CODE_PTR
+ || TYPE_CODE (TYPE_TARGET_TYPE (pfn_type)) != TYPE_CODE_FUNC)
+ return 0;
+
+ /* Look for the "this" argument. */
+ pfn_type = TYPE_TARGET_TYPE (pfn_type);
+ if (TYPE_NFIELDS (pfn_type) == 0
+ || TYPE_CODE (TYPE_FIELD_TYPE (pfn_type, 0)) != TYPE_CODE_PTR)
+ return 0;
+
+ domain_type = TYPE_TARGET_TYPE (TYPE_FIELD_TYPE (pfn_type, 0));
+ type = alloc_type (objfile);
+ smash_to_method_type (type, domain_type, TYPE_TARGET_TYPE (pfn_type),
+ TYPE_FIELDS (pfn_type), TYPE_NFIELDS (pfn_type),
+ TYPE_VARARGS (pfn_type));
+ type = lookup_methodptr_type (type);
+ set_die_type (die, type, cu);
+
+ return 1;
+}
/* Called when we find the DIE that starts a structure or union scope
(definition) to process all dies that define the members of the
@@ -3737,8 +3800,10 @@ read_structure_type (struct die_info *di
if (die->type)
return;
- type = alloc_type (objfile);
+ if (quirk_gcc_member_function_pointer (die, cu))
+ return;
+ type = alloc_type (objfile);
INIT_CPLUS_SPECIFIC (type);
attr = dwarf2_attr (die, DW_AT_name, cu);
if (attr && DW_STRING (attr))