Create subobject value in pretty printer

Nowadays, we create a value of subobject in pretty printer with 'address'
being used,

  value = value_from_contents_and_address (type, valaddr + embedded_offset,
					   address + embedded_offset);

  set_value_component_location (value, val);
  /* set_value_component_location resets the address, so we may
     need to set it again.  */
  if (VALUE_LVAL (value) != lval_internalvar
      && VALUE_LVAL (value) != lval_internalvar_component
      && VALUE_LVAL (value) != lval_computed)
    set_value_address (value, address + embedded_offset);

value_from_contents_and_address creates a value from memory, but the
value we are pretty-printing may not from memory at all.

Instead of using value_from_contents_and_address, we create a value
of subobject with the same location as object's but different offset.
We avoid using address in this way.  As a result, parameter 'address'
in apply_val_pretty_printer is no longer needed, we can remove it in
next step.

We've already had the location of the 'whole' value, so it is safe
to assume we can create a value of 'component' or 'suboject' value
at the same location but with different offset.

gdb:

2016-11-21  Yao Qi  <yao.qi@linaro.org>

	* guile/scm-pretty-print.c (gdbscm_apply_val_pretty_printer):
	Don't call value_from_contents_and_address and
	set_value_address.  Call value_from_component.
	* python/py-prettyprint.c (gdbpy_apply_val_pretty_printer):
	Likewise.
	* value.c (value_from_component): New function.
	* value.h (value_from_component): Likewise.
	* valarith.c (value_subscripted_rvalue): Call
	value_from_component.

1 files changed, 1 insertions, 16 deletions

diff --git a/gdb/valarith.c b/gdb/valarith.c
index 2c56110..efa41ed 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -194,7 +194,6 @@ value_subscripted_rvalue (struct value *array, LONGEST index, int lowerbound)
   struct type *elt_type = check_typedef (TYPE_TARGET_TYPE (array_type));
   ULONGEST elt_size = type_length_units (elt_type);
   ULONGEST elt_offs = elt_size * (index - lowerbound);
-  struct value *v;
 
   if (index < lowerbound || (!TYPE_ARRAY_UPPER_BOUND_IS_UNDEFINED (array_type)
 			     && elt_offs >= type_length_units (array_type)))
@@ -215,21 +214,7 @@ value_subscripted_rvalue (struct value *array, LONGEST index, int lowerbound)
       elt_type = resolve_dynamic_type (elt_type, NULL, address);
     }
 
-  if (VALUE_LVAL (array) == lval_memory && value_lazy (array))
-    v = allocate_value_lazy (elt_type);
-  else
-    {
-      v = allocate_value (elt_type);
-      value_contents_copy (v, value_embedded_offset (v),
-			   array, value_embedded_offset (array) + elt_offs,
-			   elt_size);
-    }
-
-  set_value_component_location (v, array);
-  VALUE_REGNUM (v) = VALUE_REGNUM (array);
-  VALUE_NEXT_FRAME_ID (v) = VALUE_NEXT_FRAME_ID (array);
-  set_value_offset (v, value_offset (array) + elt_offs);
-  return v;
+  return value_from_component (array, elt_type, elt_offs);
 }