On Fri, Feb 09, 2024 at 10:07:33AM -0500, Jason Merrill wrote:
> On 2/8/24 17:20, Marek Polacek wrote:
> > On Thu, Feb 08, 2024 at 04:53:45PM -0500, Jason Merrill wrote:
> > > On 2/8/24 11:51, Marek Polacek wrote:
> > > > On Thu, Feb 08, 2024 at 08:49:28AM -0500, Patrick Palka wrote:
> > > > > 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?
> > >
> > > I think it should be true since P1155, which we implement in C++20 mode
> > > and
> > > above (or rather, we implement the sequel P2266); since then we implicitly
> > > move from the function parameter.
> > >
> > > The patch looks good except that we should test this expected value.
> >
> > I could add
> > #if __cplusplus >= 202002L
> > static_assert (b, "move from the function parameter");
> > #else
> > static_assert (!b, "no move from the function parameter");
> > #endif
> >
> > but that's going to fail for C++20 and above.
>
> Ah, because treat_lvalue_as_rvalue_p doesn't recognize t as being from the
> current scope in the trailing return type. But that shouldn't be necessary:
>
> https://eel.is/c++draft/expr.prim.id.unqual#4.2 says it's move-eligible
> "if the id-expression (possibly parenthesized) is the operand of a
> throw-expression ([expr.throw]), and names an implicitly movable entity that
> belongs to a scope that does not contain the compound-statement of the
> innermost lambda-expression, try-block, or function-try-block (if any) whose
> compound-statement or ctor-initializer contains the throw-expression."
>
> here there is no enclosing lambda or try, so it seems move-eligible.
...and as a result, 't' will be an xvalue, therefore moveonly(moveonly&&)
should be used, therefore the first overload should be used, which means 'b'
is true.
> > I wonder if this is the
> > second half of the problem in 113789?
> >
> > I could comment the first static_assert and add a FIXME if that sounds good?
>
> dg-bogus would be better than commenting it out.
Ok, in this patch the only change I made is:
+#if __cplusplus >= 202002L
+static_assert (b, "move from the function parameter"); // { dg-bogus ""
"PR113853" { xfail c++20 } }
+#else
+static_assert (!b, "no move from the function parameter");
+#endif
> Will you also look into fixing the treat_ bug? That can be a separate
> patch.
I'd like to. I opened <https://gcc.gnu.org/PR113853>.
-- >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.
There's still one problem for which I opened <https://gcc.gnu.org/PR113853>.
We need to patch up treat_lvalue_as_rvalue_p and remove the dg-bogus.
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 | 33 ++++++++++++---------------
gcc/cp/parser.cc | 2 +-
gcc/cp/pt.cc | 2 +-
gcc/testsuite/g++.dg/cpp0x/sfinae69.C | 21 +++++++++++++++++
libcc1/libcp1plugin.cc | 4 ++--
7 files changed, 43 insertions(+), 26 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..ea3d6f57396 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;
@@ -621,7 +622,7 @@ build_throw (location_t loc, tree exp)
return exp;
}
- if (exp && null_node_p (exp))
+ if (exp && null_node_p (exp) && (complain & tf_warning))
warning_at (loc, 0,
"throwing NULL, which has integral, not pointer type");
@@ -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_error)
+ 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 f9abb21a9a2..9c225c095c8 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..361e0b79ba2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
@@ -0,0 +1,21 @@
+// 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{});
+#if __cplusplus >= 202002L
+static_assert (b, "move from the function parameter"); // { dg-bogus ""
"PR113853" { xfail c++20 } }
+#else
+static_assert (!b, "no move from the function parameter");
+#endif
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: 41a6d2560500a202708e7b661b8b2ad432aee3a6
--
2.43.0
