invoke_xmethod & array_view

This replaces more pointer+length with gdb::array_view.  This time,
around invoke_xmethod, and then propagating the fallout around, which
inevitably leaks to the overload resolution code.

There are several places in the code that want to grab a slice of an
array, by advancing the array pointer, and decreasing the length
pointer.  This patch introduces a pair of new
gdb::array_view::slice(...) methods to make that convenient and clear.
Unit test included.

gdb/ChangeLog:
2018-11-21  Pedro Alves  <palves@redhat.com>

	* common/array-view.h (array_view::splice(size_type, size_t)): New.
	(array_view::splice(size_type)): New.
	* eval.c (eval_call, evaluate_funcall): Adjust to use array_view.
	* extension.c (xmethod_worker::get_arg_types): Adjust to return an
	std::vector.
	(xmethod_worker::get_result_type): Adjust to use gdb::array_view.
	* extension.h: Include "common/array-view.h".
	(xmethod_worker::invoke): Adjust to use gdb::array_view.
	(xmethod_worker::get_arg_types): Adjust to return an std::vector.
	(xmethod_worker::get_result_type): Adjust to use gdb::array_view.
	(xmethod_worker::do_get_arg_types): Adjust to use std::vector.
	(xmethod_worker::do_get_result_type): Adjust to use
	gdb::array_view.
	* gdbtypes.c (rank_function): Adjust to use gdb::array_view.
	* gdbtypes.h: Include "common/array-view.h".
	(rank_function): Adjust to use gdb::array_view.
	* python/py-xmethods.c (python_xmethod_worker::invoke)
	(python_xmethod_worker::do_get_arg_types)
	(python_xmethod_worker::do_get_result_type)
	(python_xmethod_worker::invoke): Adjust to new interfaces.
	* valarith.c (value_user_defined_cpp_op, value_user_defined_op)
	(value_x_binop, value_x_unop): Adjust to use gdb::array_view.
	* valops.c (find_overload_match, find_oload_champ_namespace)
	(find_oload_champ_namespace_loop, find_oload_champ): Adjust to use
	gdb:array_view and the new xmethod_worker interfaces.
	* value.c (result_type_of_xmethod, call_xmethod): Adjust to use
	gdb::array_view.
	* value.h (find_overload_match, result_type_of_xmethod)
	(call_xmethod): Adjust to use gdb::array_view.
	* unittests/array-view-selftests.c: Add slicing tests.

1 files changed, 15 insertions, 17 deletions

diff --git a/gdb/extension.h b/gdb/extension.h
index 0c8c4ee..b9314c0 100644
--- a/gdb/extension.h
+++ b/gdb/extension.h
@@ -22,6 +22,7 @@
 
 #include "mi/mi-cmds.h" /* For PRINT_NO_VALUES, etc.  */
 #include "common/vec.h"
+#include "common/array-view.h"
 
 struct breakpoint;
 struct command_line;
@@ -186,38 +187,35 @@ struct xmethod_worker
   virtual ~xmethod_worker () = default;
 
   /* Invoke the xmethod encapsulated in this worker and return the result.
-     The method is invoked on OBJ with arguments in the ARGS array.  NARGS is
-     the length of the this array.  */
+     The method is invoked on OBJ with arguments in the ARGS array.  */
 
-  virtual value *invoke (value *obj, value **args, int nargs) = 0;
+  virtual value *invoke (value *obj, gdb::array_view<value *> args) = 0;
 
   /* Return the arg types of the xmethod encapsulated in this worker.
-     An array of arg types is returned.  The length of the array is returned in
-     NARGS.  The type of the 'this' object is returned as the first element of
-     array.  */
+     The type of the 'this' object is returned as the first element of
+     the vector.  */
 
-  type **get_arg_types (int *nargs);
+  std::vector<type *> get_arg_types ();
 
   /* Return the type of the result of the xmethod encapsulated in this worker.
-     OBJECT, ARGS, NARGS are the same as for invoke.  */
+     OBJECT and ARGS are the same as for invoke.  */
 
-  type *get_result_type (value *object, value **args, int nargs);
+  type *get_result_type (value *object, gdb::array_view<value *> args);
 
 private:
 
-  /* Return the types of the arguments the method takes.  The number of
-     arguments is returned in NARGS, and their types are returned in the array
-     ARGTYPES.  */
+  /* Return the types of the arguments the method takes.  The types
+     are returned in TYPE_ARGS, one per argument.  */
 
   virtual enum ext_lang_rc do_get_arg_types
-    (int *nargs, struct type ***arg_types) = 0;
+    (std::vector<type *> *type_args) = 0;
 
-  /* Fetch the type of the result of the method implemented by this worker.
-     OBJECT, ARGS, NARGS are the same as for the invoked method.  The result
-     type is stored in *RESULT_TYPE.  */
+  /* Fetch the type of the result of the method implemented by this
+     worker.  OBJECT and ARGS are the same as for the invoked method.
+     The result type is stored in *RESULT_TYPE.  */
 
   virtual enum ext_lang_rc do_get_result_type
-    (struct value *obj, struct value **args, int nargs,
+    (struct value *obj, gdb::array_view<value *> args,
      struct type **result_type_ptr) = 0;
 
   /* The language the xmethod worker is implemented in.  */