On Mon, Dec 06, 2021 at 04:44:06PM -0500, Jason Merrill wrote:
> Please also make this change to cp_parser_sizeof_operand, and add tests
> involving sizeof/alignof in array bounds. OK with that change.
Turns out we reject sizeof(auto(4)) because cp_parser_type_id_1 errors
"invalid use of auto". So I've added a hack to make it work; auto(x)
is *not* a type-id, so reject that parse and let it be parsed as an
expression.
FWIW, I don't think we need to clear auto_is_implicit_function_template_parm_p
in cp_parser_sizeof_operand for parameters like int[sizeof(auto(10))] because
the auto is in a declarator and auto_is_... will have been cleared already in
cp_parser_parameter_declaration before parsing the declarator. But I've added
it anyway, maybe there are other cases where it matters.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
In C++23, auto(x) is valid, so decltype(auto(x)) should also be valid,
so
void f(decltype(auto(0)));
should be just as
void f(int);
but currently, everytime we see 'auto' in a parameter-declaration-clause,
we try to synthesize_implicit_template_parm for it, creating a new template
parameter list. The code above actually has us calling s_i_t_p twice;
once from cp_parser_decltype_expr -> cp_parser_postfix_expression which
fails and then again from cp_parser_decltype_expr -> cp_parser_expression.
So it looks like we have f<auto, auto> and we accept ill-formed code.
This shows that we need to be more careful about synthesizing the
implicit template parameter. [dcl.spec.auto.general] says that "A
placeholder-type-specifier of the form type-constraintopt auto can be
used as a decl-specifier of the decl-specifier-seq of a
parameter-declaration of a function declaration or lambda-expression..."
so this patch turns off auto_is_... after we've parsed the decl-specifier-seq.
That doesn't quite cut it yet though, because we also need to handle an
auto nested in the decl-specifier:
void f(decltype(new auto{0}));
therefore the cp_parser_decltype change.
To accept "sizeof(auto{10})", the cp_parser_type_id_1 hunk rejects the
current parse if it sees an auto followed by a ( or {.
The second hunk broke lambda-generic-85713-2.C but I think the error we
issue with this patch is in fact correct, and clang++ agrees.
The r11-1913 change is OK: we need to make sure that we see '(auto)' after
decltype to go ahead with 'decltype(auto)'.
PR c++/103401
gcc/cp/ChangeLog:
* parser.c (cp_parser_decltype): Clear
auto_is_implicit_function_template_parm_p.
(cp_parser_type_id_1): Reject this parse if we see auto(x) or auto{x}.
(cp_parser_parameter_declaration): Clear
auto_is_implicit_function_template_parm_p after parsing the
decl-specifier-seq.
(cp_parser_sizeof_operand): Clear
auto_is_implicit_function_template_parm_p.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/lambda-generic-85713-2.C: Add dg-error.
* g++.dg/cpp23/auto-fncast7.C: New test.
* g++.dg/cpp23/auto-fncast8.C: New test.
* g++.dg/cpp23/auto-fncast9.C: New test.
---
gcc/cp/parser.c | 32 ++++++++++++++
.../g++.dg/cpp1y/lambda-generic-85713-2.C | 2 +-
gcc/testsuite/g++.dg/cpp23/auto-fncast7.C | 9 ++++
gcc/testsuite/g++.dg/cpp23/auto-fncast8.C | 42 +++++++++++++++++++
gcc/testsuite/g++.dg/cpp23/auto-fncast9.C | 17 ++++++++
5 files changed, 101 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
create mode 100644 gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 55e6a1a8b3a..6f9f84631e5 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -16432,6 +16432,16 @@ cp_parser_decltype (cp_parser *parser)
= parser->greater_than_is_operator_p;
parser->greater_than_is_operator_p = true;
+ /* Don't synthesize an implicit template type parameter here. This
+ could happen with C++23 code like
+
+ void f(decltype(new auto{0}));
+
+ where we want to deduce the auto right away so that the parameter
+ is of type 'int *'. */
+ auto cleanup = make_temp_override
+ (parser->auto_is_implicit_function_template_parm_p, false);
+
/* Do not actually evaluate the expression. */
++cp_unevaluated_operand;
@@ -24142,6 +24152,16 @@ cp_parser_type_id_1 (cp_parser *parser,
cp_parser_flags flags,
/* OK */;
else if (parser->in_result_type_constraint_p)
/* OK */;
+ else if ((cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE)
+ || cp_lexer_next_token_is (parser->lexer, CPP_OPEN_PAREN))
+ && TYPE_IDENTIFIER (auto_node) == auto_identifier)
+ {
+ /* This is C++23 auto(x) or auto{x}, which is valid, but it
+ certainly isn't a type-id. */
+ gcc_assert (cp_parser_uncommitted_to_tentative_parse_p (parser));
+ cp_parser_simulate_error (parser);
+ return error_mark_node;
+ }
else
{
location_t loc = type_specifier_seq.locations[ds_type_spec];
@@ -24668,6 +24688,15 @@ cp_parser_parameter_declaration (cp_parser *parser,
&decl_specifiers,
&declares_class_or_enum);
+ /* [dcl.spec.auto.general]: "A placeholder-type-specifier of the form
+ type-constraint opt auto can be used as a decl-specifier of the
+ decl-specifier-seq of a parameter-declaration of a function declaration
+ or lambda-expression..." but we must not synthesize an implicit template
+ type parameter in its declarator. That is, in "void f(auto[auto{10}]);"
+ we want to synthesize only the first auto. */
+ auto cleanup = make_temp_override
+ (parser->auto_is_implicit_function_template_parm_p, false);
+
/* Complain about missing 'typename' or other invalid type names. */
if (!decl_specifiers.any_type_specifiers_p
&& cp_parser_parse_and_diagnose_invalid_type_name (parser))
@@ -32369,6 +32398,9 @@ cp_parser_sizeof_operand (cp_parser* parser, enum rid
keyword)
= parser->non_integral_constant_expression_p;
parser->integral_constant_expression_p = false;
+ auto cleanup = make_temp_override
+ (parser->auto_is_implicit_function_template_parm_p, false);
+
/* Do not actually evaluate the expression. */
++cp_unevaluated_operand;
++c_inhibit_evaluation_warnings;
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-85713-2.C
b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-85713-2.C
index 8fb8dfdeaf0..dbc9e8c732c 100644
--- a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-85713-2.C
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-85713-2.C
@@ -2,6 +2,6 @@
// { dg-do compile { target c++14 } }
auto l4 = [](auto v, auto (&array (int)) [5]) -> int { return v + array[0]; };
-auto l5 = [](auto v, auto (&array (auto)) [5]) -> int { return v + array[0]; };
+auto l5 = [](auto v, auto (&array (auto)) [5]) -> int { return v + array[0];
}; // { dg-error ".auto. parameter not permitted in this context" }
auto l6 = [](auto v, auto (&array (int int)) [5]) -> int { return v +
array[0]; }; // { dg-error "two or more data types" }
auto l7 = [](auto v, auto (&array (int auto)) [5]) -> int { return v +
array[0]; }; // { dg-error "two or more data types" }
diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
b/gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
new file mode 100644
index 00000000000..763164f3e5b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast7.C
@@ -0,0 +1,9 @@
+// PR c++/103401
+// { dg-do compile { target c++23 } }
+
+void f(decltype(auto(0))) { }
+
+int main()
+{
+ f<int,int>(0); // { dg-error "no matching function" }
+}
diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
b/gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
new file mode 100644
index 00000000000..9fb7b9c2516
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast8.C
@@ -0,0 +1,42 @@
+// PR c++/103401
+// { dg-do compile { target c++23 } }
+
+void f1 (decltype(auto(0)));
+void f2 (decltype(auto{0}));
+void f3 (int = auto(42));
+void f4 (int = auto{42});
+void f5 (decltype(auto(0)) = auto(42));
+void f6 (auto (x));
+void f7 (int[auto(10)]);
+void f8 (int[auto{10}]);
+void f9 (auto[auto{10}]);
+void f10 (auto);
+void f11 (int x, decltype(x) y);
+void f12 (int[sizeof(auto{10})]);
+void f13 (int[sizeof(auto(10))]);
+void f14 (int[__extension__ alignof(auto{10})]);
+void f15 (int[__extension__ alignof(auto(10))]);
+
+void
+g ()
+{
+ int a[2];
+ f1 (1);
+ f2 (1);
+ f3 ();
+ f3 (1);
+ f4 ();
+ f4 (1);
+ f5 ();
+ f5 (1);
+ f6 ('a');
+ f7 (&a[0]);
+ f8 (&a[0]);
+ f9 (&a[0]);
+ f10 (1);
+ f11 (1, 2);
+ f12 (&a[0]);
+ f13 (&a[0]);
+ f14 (&a[0]);
+ f15 (&a[0]);
+}
diff --git a/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
b/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
new file mode 100644
index 00000000000..12a0dcece75
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/auto-fncast9.C
@@ -0,0 +1,17 @@
+// PR c++/103401
+// { dg-do compile { target c++23 } }
+
+void f1(decltype(new auto{0}));
+void f2(decltype(new int{0}));
+
+void
+g ()
+{
+ int i;
+ void f3(decltype(new auto{0}));
+ void f4(decltype(new int{0}));
+ f1 (&i);
+ f2 (&i);
+ f3 (&i);
+ f4 (&i);
+}
base-commit: 9eec77c0df9e5c67454a2e8f83246104458ba4f0
--
2.33.1
