On Wed, 7 Feb 2024, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> -- >8 --
> Here the problem is that we give hard errors while substituting
> template parameters during overload resolution of is_throwable
> which has an invalid throw in decltype.
>
> The backtrace shows that fn_type_unification -> instantiate_template
> -> tsubst* passes complain=0 as expected, but build_throw doesn't
> have a complain parameter. So let's add one. Also remove a redundant
> local variable which I should have removed in my P2266 patch.
>
> But there's still something not quite clear to me. I claim that 'b'
> in the testcase should evaluate to false since the first overload ought
> to have been discarded. EDG 6.6 agrees, but clang++, msvc, and icx evaluate
> it to true. Who's right?
>
> Thanks to Patrick for notifying me of this PR. This doesn't fully fix
> 113789; there I think I'll have to figure our why a candidate wasn't
> discarded from the overload set.
>
> gcc/cp/ChangeLog:
>
> * coroutines.cc (coro_rewrite_function_body): Pass tf_warning_or_error
> to build_throw.
> (morph_fn_to_coro): Likewise.
> * cp-tree.h (build_throw): Adjust.
> * except.cc (expand_end_catch_block): Pass tf_warning_or_error to
> build_throw.
> (build_throw): Add a tsubst_flags_t parameter. Use it. Remove
> redundant variable. Guard an inform call.
> * parser.cc (cp_parser_throw_expression): Pass tf_warning_or_error
> to build_throw.
> * pt.cc (tsubst_expr) <case THROW_EXPR>: Pass complain to build_throw.
>
> libcc1/ChangeLog:
>
> * libcp1plugin.cc (plugin_build_unary_expr): Pass tf_error to
> build_throw.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/sfinae69.C: New test.
> ---
> gcc/cp/coroutines.cc | 4 ++--
> gcc/cp/cp-tree.h | 3 ++-
> gcc/cp/except.cc | 31 +++++++++++----------------
> gcc/cp/parser.cc | 2 +-
> gcc/cp/pt.cc | 2 +-
> gcc/testsuite/g++.dg/cpp0x/sfinae69.C | 16 ++++++++++++++
> libcc1/libcp1plugin.cc | 4 ++--
> 7 files changed, 37 insertions(+), 25 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae69.C
>
> diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
> index 3194c911e8c..9b037edbd14 100644
> --- a/gcc/cp/coroutines.cc
> +++ b/gcc/cp/coroutines.cc
> @@ -4246,7 +4246,7 @@ coro_rewrite_function_body (location_t fn_start, tree
> fnbody, tree orig,
> boolean_type_node, i_a_r_c);
> finish_if_stmt_cond (not_iarc, not_iarc_if);
> /* If the initial await resume called value is false, rethrow... */
> - tree rethrow = build_throw (fn_start, NULL_TREE);
> + tree rethrow = build_throw (fn_start, NULL_TREE, tf_warning_or_error);
> suppress_warning (rethrow);
> finish_expr_stmt (rethrow);
> finish_then_clause (not_iarc_if);
> @@ -5151,7 +5151,7 @@ morph_fn_to_coro (tree orig, tree *resumer, tree
> *destroyer)
> tree del_coro_fr = coro_get_frame_dtor (coro_fp, orig, frame_size,
> promise_type, fn_start);
> finish_expr_stmt (del_coro_fr);
> - tree rethrow = build_throw (fn_start, NULL_TREE);
> + tree rethrow = build_throw (fn_start, NULL_TREE, tf_warning_or_error);
> suppress_warning (rethrow);
> finish_expr_stmt (rethrow);
> finish_handler (handler);
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 969c7239c97..334c11396c2 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -7185,7 +7185,8 @@ extern void init_exception_processing (void);
> extern tree expand_start_catch_block (tree);
> extern void expand_end_catch_block (void);
> extern tree build_exc_ptr (void);
> -extern tree build_throw (location_t, tree);
> +extern tree build_throw (location_t, tree,
> + tsubst_flags_t);
> extern int nothrow_libfn_p (const_tree);
> extern void check_handlers (tree);
> extern tree finish_noexcept_expr (tree, tsubst_flags_t);
> diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
> index d17a57d3fbc..ed704b6c28a 100644
> --- a/gcc/cp/except.cc
> +++ b/gcc/cp/except.cc
> @@ -486,7 +486,8 @@ expand_end_catch_block (void)
> || DECL_DESTRUCTOR_P (current_function_decl))
> && !in_nested_catch ())
> {
> - tree rethrow = build_throw (input_location, NULL_TREE);
> + tree rethrow = build_throw (input_location, NULL_TREE,
> + tf_warning_or_error);
> /* Disable all warnings for the generated rethrow statement. */
> suppress_warning (rethrow);
> finish_expr_stmt (rethrow);
> @@ -607,7 +608,7 @@ wrap_cleanups_r (tree *tp, int *walk_subtrees, void *
> /*data*/)
> /* Build a throw expression. */
>
> tree
> -build_throw (location_t loc, tree exp)
> +build_throw (location_t loc, tree exp, tsubst_flags_t complain)
> {
> if (exp == error_mark_node)
> return exp;
The "throwing NULL, which has integral, not pointer type" warning near
the top of build_throw should probably be guarded by tf_warning now.
> @@ -642,8 +643,6 @@ build_throw (location_t loc, tree exp)
> tree object, ptr;
> tree allocate_expr;
>
> - tsubst_flags_t complain = tf_warning_or_error;
> -
> /* The CLEANUP_TYPE is the internal type of a destructor. */
> if (!cleanup_type)
> {
> @@ -714,7 +713,6 @@ build_throw (location_t loc, tree exp)
> if (CLASS_TYPE_P (temp_type))
> {
> int flags = LOOKUP_NORMAL | LOOKUP_ONLYCONVERTING;
> - bool converted = false;
> location_t exp_loc = cp_expr_loc_or_loc (exp, loc);
>
> /* Under C++0x [12.8/16 class.copy], a thrown lvalue is sometimes
> @@ -727,23 +725,20 @@ build_throw (location_t loc, tree exp)
> exp = moved;
>
> /* Call the copy constructor. */
> - if (!converted)
> - {
> - releasing_vec exp_vec (make_tree_vector_single (exp));
> - exp = (build_special_member_call
> - (object, complete_ctor_identifier, &exp_vec,
> - TREE_TYPE (object), flags, tf_warning_or_error));
> - }
> -
> + releasing_vec exp_vec (make_tree_vector_single (exp));
> + exp = build_special_member_call (object, complete_ctor_identifier,
> + &exp_vec, TREE_TYPE (object), flags,
> + complain);
> if (exp == error_mark_node)
> {
> - inform (exp_loc, " in thrown expression");
> + if (complain & tf_warning)
tf_error instead of tf_warning for this note?
> + inform (exp_loc, " in thrown expression");
> return error_mark_node;
> }
> }
> else
> {
> - tree tmp = decay_conversion (exp, tf_warning_or_error);
> + tree tmp = decay_conversion (exp, complain);
> if (tmp == error_mark_node)
> return error_mark_node;
> exp = cp_build_init_expr (object, tmp);
> @@ -768,7 +763,7 @@ build_throw (location_t loc, tree exp)
> tree binfo = TYPE_BINFO (TREE_TYPE (object));
> tree dtor_fn = lookup_fnfields (binfo,
> complete_dtor_identifier, 0,
> - tf_warning_or_error);
> + complain);
> dtor_fn = BASELINK_FUNCTIONS (dtor_fn);
> if (!mark_used (dtor_fn)
> || !perform_or_defer_access_check (binfo, dtor_fn,
> @@ -785,7 +780,7 @@ build_throw (location_t loc, tree exp)
> cleanup = build_int_cst (cleanup_type, 0);
>
> /* ??? Indicate that this function call throws throw_type. */
> - tree tmp = cp_build_function_call_nary (throw_fn, tf_warning_or_error,
> + tree tmp = cp_build_function_call_nary (throw_fn, complain,
> ptr, throw_type, cleanup,
> NULL_TREE);
>
> @@ -807,7 +802,7 @@ build_throw (location_t loc, tree exp)
>
> /* ??? Indicate that this function call allows exceptions of the type
> of the enclosing catch block (if known). */
> - exp = cp_build_function_call_vec (rethrow_fn, NULL,
> tf_warning_or_error);
> + exp = cp_build_function_call_vec (rethrow_fn, NULL, complain);
> }
>
> exp = build1_loc (loc, THROW_EXPR, void_type_node, exp);
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index c4292c49ce2..09ecfa23b5d 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -29310,7 +29310,7 @@ cp_parser_throw_expression (cp_parser* parser)
> the end at the end of the final token we consumed. */
> location_t combined_loc = make_location (start_loc, start_loc,
> parser->lexer);
> - expression = build_throw (combined_loc, expression);
> + expression = build_throw (combined_loc, expression, tf_warning_or_error);
>
> return expression;
> }
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 55c23b642bc..1a8f9b20e30 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -21180,7 +21180,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
> complain, tree in_decl)
>
> case THROW_EXPR:
> RETURN (build_throw
> - (input_location, RECUR (TREE_OPERAND (t, 0))));
> + (input_location, RECUR (TREE_OPERAND (t, 0)), complain));
>
> case CONSTRUCTOR:
> {
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> new file mode 100644
> index 00000000000..c4896050b9d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> @@ -0,0 +1,16 @@
> +// PR c++/98388
> +// { dg-do compile { target c++11 } }
> +
> +struct moveonly {
> + moveonly() = default;
> + moveonly(moveonly&&) = default;
> +};
> +
> +template<class T>
> +constexpr auto is_throwable(T t) -> decltype(throw t, true) {
> + return true;
> +}
> +template<class T>
> +constexpr bool is_throwable(...) { return false; }
> +
> +constexpr bool b = is_throwable<moveonly>(moveonly{});
> diff --git a/libcc1/libcp1plugin.cc b/libcc1/libcp1plugin.cc
> index 7f4e4c98060..0eff7c68d29 100644
> --- a/libcc1/libcp1plugin.cc
> +++ b/libcc1/libcp1plugin.cc
> @@ -2640,7 +2640,7 @@ plugin_build_unary_expr (cc1_plugin::connection *self,
> break;
>
> case THROW_EXPR:
> - result = build_throw (input_location, op0);
> + result = build_throw (input_location, op0, tf_error);
> break;
>
> case TYPEID_EXPR:
> @@ -2664,7 +2664,7 @@ plugin_build_unary_expr (cc1_plugin::connection *self,
> result = make_pack_expansion (op0);
> break;
>
> - // We're using this for sizeof...(pack). */
> + /* We're using this for sizeof...(pack). */
> case TYPE_PACK_EXPANSION:
> result = make_pack_expansion (op0);
> PACK_EXPANSION_SIZEOF_P (result) = true;
>
> base-commit: bfd72bb44eca83b0db2b0bab895f27a8a44247a2
> --
> 2.43.0
>
>
