gdb/

2009-02-06  Jim Blandy  <jimb@codesourcery.com>
	    Daniel Jacobowitz  <dan@codesourcery.com>
	    Vladimir Prus  <vladimir@codesourcery.com>
	    Pedro Alves  <pedro@codesourcery.com>

	* defs.h (enum lval_type): New value: lval_computed.
	* value.h (struct lval_funcs): New type.
	(allocate_computed_value, value_computed_funcs)
	(value_computed_closure): New declarations.
	* value.c (struct value): Add a structure to the location union
	for computed lvalues, containing 'funcs' and 'closure' members.
	(allocate_computed_value, value_computed_funcs)
	(value_computed_closure): New functions.
	(value_free): For computed lvalues, call the closure's
	'free_closure' function before freeing the value itself.
	(value_copy): If we're copying an lval_computed value, call the
	closure's 'copy_closure' function.
	(set_value_component_location): If the original value is a
	computed lvalue, then call the closure's 'copy_closure' function.
	(value_of_internalvar): If an internal variable's value is a
	computed lvalue, make retrieving its value produce an equivalent
	computed lvalue.
	* valops.c (value_fetch_lazy): Unlazy computed lvalues by calling
	their read function.
	(value_assign): Assign to computed lvalues by calling their write
	function.

gdb/doc/
2009-02-06  Pedro Alves  <pedro@codesourcery.com>

	* gdbint.texinfo (Values): New chapter.

1 files changed, 54 insertions, 0 deletions

diff --git a/gdb/value.h b/gdb/value.h
index 9a11190..0c85223 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -142,6 +142,60 @@ extern void set_value_pointed_to_offset (struct value *value, int val);
 extern int value_embedded_offset (struct value *value);
 extern void set_value_embedded_offset (struct value *value, int val);
 
+/* For lval_computed values, this structure holds functions used to
+   retrieve and set the value (or portions of the value).
+
+   For each function, 'V' is the 'this' pointer: an lval_funcs
+   function F may always assume that the V it receives is an
+   lval_computed value, and has F in the appropriate slot of its
+   lval_funcs structure.  */
+
+struct lval_funcs
+{
+  /* Fill in VALUE's contents.  This is used to "un-lazy" values.  If
+     a problem arises in obtaining VALUE's bits, this function should
+     call 'error'.  */
+  void (*read) (struct value *v);
+
+  /* Handle an assignment TOVAL = FROMVAL by writing the value of
+     FROMVAL to TOVAL's location.  The contents of TOVAL have not yet
+     been updated.  If a problem arises in doing so, this function
+     should call 'error'.  */
+  void (*write) (struct value *toval, struct value *fromval);
+
+  /* Return a duplicate of VALUE's closure, for use in a new value.
+     This may simply return the same closure, if VALUE's is
+     reference-counted or statically allocated.
+
+     This may be NULL, in which case VALUE's closure is re-used in the
+     new value.  */
+  void *(*copy_closure) (struct value *v);
+
+  /* Drop VALUE's reference to its closure.  Maybe this frees the
+     closure; maybe this decrements a reference count; maybe the
+     closure is statically allocated and this does nothing.
+
+     This may be NULL, in which case no action is taken to free
+     VALUE's closure.  */
+  void (*free_closure) (struct value *v);
+};
+
+/* Create a computed lvalue, with type TYPE, function pointers FUNCS,
+   and closure CLOSURE.  */
+
+extern struct value *allocate_computed_value (struct type *type,
+                                              struct lval_funcs *funcs,
+                                              void *closure);
+
+/* If VALUE is lval_computed, return its lval_funcs structure.  */
+
+extern struct lval_funcs *value_computed_funcs (struct value *value);
+
+/* If VALUE is lval_computed, return its closure.  The meaning of the
+   returned value depends on the functions VALUE uses.  */
+
+extern void *value_computed_closure (struct value *value);
+
 /* If zero, contents of this value are in the contents field.  If
    nonzero, contents are in inferior.  If the lval field is lval_memory,
    the contents are in inferior memory at location.address plus offset.