ada-lang.c:coerce_unspec_val_to_type: Preserve laziness.

ada-lang.c:coerce_unspec_val_to_type does:

      if (value_lazy (val)
	  || TYPE_LENGTH (type) > TYPE_LENGTH (value_type (val)))
	result = allocate_value_lazy (type);
      else
	{
	  result = allocate_value (type);
	  memcpy (value_contents_raw (result), value_contents (val),
		  TYPE_LENGTH (type));
	}
      set_value_component_location (result, val);
      set_value_bitsize (result, value_bitsize (val));
      set_value_bitpos (result, value_bitpos (val));
      set_value_address (result, value_address (val));
      set_value_optimized_out (result, value_optimized_out (val));

Notice that before value_optimized_out was made to auto-fetch lazy
values, VAL would end up still lazy if it was lazy on entry.  It's not
really a problem here if VAL is lazy, and VAL->optimized_out is 0,
because RESULT is also left lazy.  IOW, this just wants to copy the
VAL->optimized_out flag to RESULT->optimized_out, nothing else.

As a side-effect of the change in value_optimized_out, the following
testcase now regresses. Consider:

       type Small is range -64 .. 63;
       for Small'Size use 7;
       type Arr is array (1..10) of Small;
       pragma Pack (Arr);

       type Arr_Ptr is access Arr;
       An_Arr_Ptr : Arr_Ptr := new Arr'(10, 20, 30, 40, 50, 60, 62, 63,
                                        -23, 42);

    Trying to print one element of An_Arr_Ptr yields:

        (gdb) p an_arr_ptr(3)
        Cannot access memory at address 0x0

The patch adds the value_optimized_out_const function for that,
allowing us to avoid trying to fetch a value at a dummy address.

(I found this out by grepping for set_value_optimized_out and trying
to convert the uses I found to instead allocate the value with
allocate_optimized_out_value.)

Tested on x86_64 Fedora 17.

gdb/
2013-07-09  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (coerce_unspec_val_to_type): Use
	value_optimized_out_const.
	* value.c (value_optimized_out_const): New function.
	* value.h (value_optimized_out_const): New declaration.

1 files changed, 7 insertions, 1 deletions

diff --git a/gdb/value.h b/gdb/value.h
index 44d2aa0..5e00c89 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -319,10 +319,16 @@ extern int value_fetch_lazy (struct value *val);
 extern int value_contents_equal (struct value *val1, struct value *val2);
 
 /* If nonzero, this is the value of a variable which does not actually
-   exist in the program.  */
+   exist in the program, at least partially.  If the value is lazy,
+   this may fetch it now.  */
 extern int value_optimized_out (struct value *value);
 extern void set_value_optimized_out (struct value *value, int val);
 
+/* Like value_optimized_out, but don't fetch the value even if it is
+   lazy.  Mainly useful for constructing other values using VALUE as
+   template.  */
+extern int value_optimized_out_const (const struct value *value);
+
 /* Like value_optimized_out, but return false if any bit in the object
    is valid.  */
 extern int value_entirely_optimized_out (const struct value *value);