Use gdb:array_view in call_function_by_hand & friends

This replaces a few uses of pointer+length with gdb::array_view, in
call_function_by_hand and related code.

Unfortunately, due to -Wnarrowing, there are places where we can't
brace-initialize an gdb::array_view without an ugly-ish cast.  To
avoid the cast, this patch introduces a gdb::make_array_view function.
Unit tests included.

This patch in isolation may not look so interesting, due to
gdb::make_array_view uses, but I think it's still worth it.  Some of
the gdb::make_array_view calls disappear down the series, and others
could be eliminated with more (non-trivial) gdb::array_view
detangling/conversion (e.g. code around eval_call).  See this as a "we
have to start somewhere" patch.

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

	* ada-lang.c (ada_evaluate_subexp): Adjust to pass an array_view.
	* common/array-view.h (make_array_view): New.
	* compile/compile-object-run.c (compile_object_run): Adjust to
	pass an array_view.
	* elfread.c (elf_gnu_ifunc_resolve_addr): Adjust.
	* eval.c (eval_call): Adjust to pass an array_view.
	(evaluate_subexp_standard): Adjust to pass an array_view.
	* gcore.c (call_target_sbrk): Adjust to pass an array_view.
	* guile/scm-value.c (gdbscm_value_call): Likewise.
	* infcall.c (push_dummy_code): Replace pointer + size parameters
	with an array_view parameter.
	(call_function_by_hand, call_function_by_hand_dummy): Likewise and
	adjust.
	* infcall.h: Include "common/array-view.h".
	(call_function_by_hand, call_function_by_hand_dummy): Replace
	pointer + size parameters with an array_view parameter.
	* linux-fork.c (inferior_call_waitpid): Adjust to use array_view.
	* linux-tdep.c (linux_infcall_mmap): Likewise.
	* objc-lang.c (lookup_objc_class, lookup_child_selector)
	(value_nsstring, print_object_command): Likewise.
	* python/py-value.c (valpy_call): Likewise.
	* rust-lang.c (rust_evaluate_funcall): Likewise.
	* spu-tdep.c (flush_ea_cache): Likewise.
	* valarith.c (value_x_binop, value_x_unop): Likewise.
	* valops.c (value_allocate_space_in_inferior): Likewise.
	* unittests/array-view-selftests.c (run_tests): Add
	gdb::make_array_view test.

1 files changed, 42 insertions, 0 deletions

diff --git a/gdb/common/array-view.h b/gdb/common/array-view.h
index 319ea99..9c5fa2a 100644
--- a/gdb/common/array-view.h
+++ b/gdb/common/array-view.h
@@ -201,6 +201,48 @@ operator!= (const gdb::array_view<T> &lhs, const gdb::array_view<T> &rhs)
   return !(lhs == rhs);
 }
 
+/* Create an array view from a pointer to an array and an element
+   count.
+
+   This is useful as alternative to constructing an array_view using
+   brace initialization when the size variable you have handy is of
+   signed type, since otherwise without an explicit cast the code
+   would be ill-formed.
+
+   For example, with:
+
+     extern void foo (int, int, gdb::array_view<value *>);
+
+     value *args[2];
+     int nargs;
+     foo (1, 2, {values, nargs});
+
+   You'd get:
+
+     source.c:10: error: narrowing conversion of ‘nargs’ from ‘int’ to
+     ‘size_t {aka long unsigned int}’ inside { } [-Werror=narrowing]
+
+   You could fix it by writing the somewhat distracting explicit cast:
+
+     foo (1, 2, {values, (size_t) nargs});
+
+   Or by instantiating an array_view explicitly:
+
+     foo (1, 2, gdb::array_view<value *>(values, nargs));
+
+   Or, better, using make_array_view, which has the advantage of
+   inferring the arrav_view element's type:
+
+     foo (1, 2, gdb::make_array_view (values, nargs));
+*/
+
+template<typename U>
+constexpr inline array_view<U>
+make_array_view (U *array, size_t size) noexcept
+{
+  return {array, size};
+}
+
 } /* namespace gdb */
 
 #endif