gdb/

* exceptions.h (NOT_AVAILABLE_ERROR): New error.
	* value.c: Include "exceptions.h".
	(require_available): Throw NOT_AVAILABLE_ERROR instead of a
	generic error.
	* cp-abi.c: Include gdb_assert.h.
	(baseclass_offset): Add `embedded_offset' and `val' parameters.
	Assert the method is implemented.  Wrap NOT_AVAILABLE_ERROR
	errors.
	* cp-abi.h (baseclass_offset): Add `embedded_offset' and `val'
	parameters.  No longer returns -1 on error.
	(struct cp_abi_ops) <baseclass_offset>: Add `embedded_offset' and
	`val' parameters.
	* cp-valprint.c: Include exceptions.h.
	(cp_print_value): Handle NOT_AVAILABLE_ERROR errors when fetching
	the baseclass_offset.  Handle unavailable base classes.  Use
	val_print_invalid_address.
	* p-valprint.c: Include exceptions.h.
	(pascal_object_print_value): Handle NOT_AVAILABLE_ERROR errors
	when fetching the baseclass_offset.  No longer expect
	baseclass_offset returning -1.  Handle unavailable base classes.
	Use val_print_invalid_address.
	* valops.c (dynamic_cast_check_1): Rename `contents' parameter to
	`valaddr' parameter, and change its type to gdb_byte pointer.  Add
	`embedded_offset' and `val' parameters.  Adjust.
	(dynamic_cast_check_2): Rename `contents' parameter to `valaddr'
	parameter, and change its type to gdb_byte pointer.  Add
	`embedded_offset' and `val' parameters.  Adjust.  No longer expect
	baseclass_offset returning -1.
	(value_dynamic_cast): Use value_contents_for_printing rather than
	value_contents.  Adjust.
	(search_struct_field): No longer expect baseclass_offset returning
	-1.
	(search_struct_method): If reading memory from the target is
	necessary, wrap it in a new value to pass to baseclass_offset.  No
	longer expect baseclass_offset returning -1.
	(find_method_list): No longer expect baseclass_offset returning
	-1.  Use value_contents_for_printing rather than value_contents.
	* valprint.c (val_print_invalid_address): New function.
	* valprint.h (val_print_invalid_address): Declare.
	* gdbtypes.c (is_unique_ancestor_worker): New `embedded_offset'
	and `val' parameters.  No longer expect baseclass_offset returning
	-1.  Adjust.
	* gnu-v2-abi.c: Include "exceptions.h".
	(gnuv2_baseclass_offset): Add `embedded_offset' and `val'
	parameters.  Handle unavailable memory.  Recurse through
	gnuv2_baseclass_offset directly, rather than through
	baseclass_offset.  No longer returns -1 on not found, instead
	throw an error.
	* gnu-v3-abi.c (gnuv3_baseclass_offset): Add `embedded_offset' and
	`val' parameters.  Adjust.

	gdb/testsuite/
	* gdb.trace/unavailable.cc (class Base, class Middle, class
	Derived): New types.
	(derived_unavail, derived_partial, derived_whole): New globals.
	(virtual_partial): New global.
	(virtualp): Point at virtual_partial.
	* gdb.trace/unavailable.exp (gdb_collect_globals_test): Add tests
	related to unavailable vptr.

gdb/gnu-v2-abi.c

@@ -28,6 +28,7 @@
 #include "demangle.h"
 #include "cp-abi.h"
 #include "cp-support.h"
+#include "exceptions.h"
 
 #include <ctype.h>
 
@@ -334,17 +335,15 @@ vb_match (struct type *type, int index, struct type *basetype)
   return 0;
 }
 
-/* Compute the offset of the baseclass which is
-   the INDEXth baseclass of class TYPE,
-   for value at VALADDR (in host) at ADDRESS (in target).
-   The result is the offset of the baseclass value relative
-   to (the address of)(ARG) + OFFSET.
-
-   -1 is returned on error.  */
+/* Compute the offset of the baseclass which is the INDEXth baseclass
+   of class TYPE, for value at VALADDR (in host) at ADDRESS (in
+   target).  The result is the offset of the baseclass value relative
+   to (the address of)(ARG) + OFFSET.  */
 
 static int
 gnuv2_baseclass_offset (struct type *type, int index,
-			const bfd_byte *valaddr, CORE_ADDR address)
+			const bfd_byte *valaddr, int embedded_offset,
+			CORE_ADDR address, const struct value *val)
 {
   struct type *basetype = TYPE_BASECLASS (type, index);
 
@@ -360,24 +359,41 @@ gnuv2_baseclass_offset (struct type *type, int index,
 	{
 	  if (vb_match (type, i, basetype))
 	    {
-	      CORE_ADDR addr
-		= unpack_pointer (TYPE_FIELD_TYPE (type, i),
-				  valaddr + (TYPE_FIELD_BITPOS (type, i) / 8));
+	      struct type *field_type;
+	      int field_offset;
+	      int field_length;
+	      CORE_ADDR addr;
 
-	      return addr - (LONGEST) address;
+	      field_type = check_typedef (TYPE_FIELD_TYPE (type, i));
+	      field_offset = TYPE_FIELD_BITPOS (type, i) / 8;
+	      field_length = TYPE_LENGTH (field_type);
+
+	      if (!value_bytes_available (val, embedded_offset + field_offset,
+					  field_length))
+		throw_error (NOT_AVAILABLE_ERROR,
+			     _("Virtual baseclass pointer is not available"));
+
+	      addr = unpack_pointer (field_type,
+				     valaddr + embedded_offset + field_offset);
+
+	      return addr - (LONGEST) address + embedded_offset;
 	    }
 	}
       /* Not in the fields, so try looking through the baseclasses.  */
       for (i = index + 1; i < n_baseclasses; i++)
 	{
+	  /* Don't go through baseclass_offset, as that wraps
+	     exceptions, thus, inner exceptions would be wrapped more
+	     than once.  */
 	  int boffset =
-	    baseclass_offset (type, i, valaddr, address);
+	    gnuv2_baseclass_offset (type, i, valaddr,
+				    embedded_offset, address, val);
 
 	  if (boffset)
 	    return boffset;
 	}
-      /* Not found.  */
-      return -1;
+
+      error (_("Baseclass offset not found"));
     }
 
   /* Baseclass is easily computed.  */