From: Jason Merrill <jason@redhat.com>
To: Marek Polacek <polacek@redhat.com>,
GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] c++: C++20 DR 2237, disallow simple-template-id in cdtor.
Date: Wed, 20 May 2020 16:45:32 -0400 [thread overview]
Message-ID: <963daa42-02d8-37d0-c5bd-6edb7cce3a18@redhat.com> (raw)
In-Reply-To: <20200520180548.GM3766@redhat.com>
On 5/20/20 2:05 PM, Marek Polacek wrote:
> Ping.
OK (with 2a->20, of course).
Jason
> On Mon, May 11, 2020 at 04:23:17PM -0400, Marek Polacek via Gcc-patches wrote:
>> On Sun, Apr 05, 2020 at 09:46:09PM -0400, Jason Merrill wrote:
>>> On 4/4/20 7:30 PM, Marek Polacek wrote:
>>>> This patch implements DR 2237 which says that a simple-template-id is
>>>> no longer valid as the declarator-id of a constructor or destructor;
>>>> see <https://eel.is/c++draft/diff.cpp17.class#2>. It is not explicitly
>>>> stated but out-of-line destructors with a simple-template-id are also
>>>> meant to be ill-formed now. (Out-of-line constructors like that are
>>>> invalid since DR1435 I think.) This change only applies to C++20; it
>>>> is not a DR against C++17.
>>>>
>>>> I'm not crazy about the diagnostic in constructors but ISTM that
>>>> cp_parser_constructor_declarator_p shouldn't print errors.
>>>>
>>>> Does it seem reasonable to apply this now or should I defer to GCC 11?
>>>
>>> A new error should wait for GCC 11.
>>
>> Coming back to this now that we're again in stage 1.
>>
>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>>
>>>> 2020-04-04 Marek Polacek <polacek@redhat.com>
>>>>
>>>> DR 2237
>>>> * parser.c (cp_parser_unqualified_id): Reject simple-template-id as
>>>> the declarator-id of a destructor.
>>>> (cp_parser_constructor_declarator_p): Reject simple-template-id as
>>>> the declarator-id of a constructor.
>>>>
>>>> * g++.dg/DRs/dr2237.C: New test.
>>>> * g++.dg/parse/constructor2.C: Add dg-error for C++20.
>>>> * g++.dg/parse/dtor12.C: Likewise.
>>>> * g++.dg/parse/dtor4.C: Likewise.
>>>> * g++.dg/template/dtor4.C: Adjust dg-error.
>>>> * g++.dg/template/error34.C: Likewise.
>>>> * g++.old-deja/g++.other/inline15.C: Only run for C++17 and lesses.
>>>> * g++.old-deja/g++.pt/ctor2.C: Add dg-error for C++20.
>>>> ---
>>>> gcc/cp/parser.c | 16 ++++++++++++++++
>>>> gcc/testsuite/g++.dg/DRs/dr2237.C | 18 ++++++++++++++++++
>>>> gcc/testsuite/g++.dg/parse/constructor2.C | 4 ++--
>>>> gcc/testsuite/g++.dg/parse/dtor12.C | 2 +-
>>>> gcc/testsuite/g++.dg/parse/dtor4.C | 2 +-
>>>> gcc/testsuite/g++.dg/template/dtor4.C | 2 +-
>>>> gcc/testsuite/g++.dg/template/error34.C | 10 +++++-----
>>>> .../g++.old-deja/g++.other/inline15.C | 2 +-
>>>> gcc/testsuite/g++.old-deja/g++.pt/ctor2.C | 2 +-
>>>> 9 files changed, 46 insertions(+), 12 deletions(-)
>>>> create mode 100644 gcc/testsuite/g++.dg/DRs/dr2237.C
>>>>
>>>> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
>>>> index 7e5921e039f..810edfa87a9 100644
>>>> --- a/gcc/cp/parser.c
>>>> +++ b/gcc/cp/parser.c
>>>> @@ -6114,6 +6114,16 @@ cp_parser_unqualified_id (cp_parser* parser,
>>>> return build_min_nt_loc (loc, BIT_NOT_EXPR, make_auto ());
>>>> }
>>>> + /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
>>>> + declarator-id of a constructor or destructor. */
>>>> + if (token->type == CPP_TEMPLATE_ID && cxx_dialect >= cxx2a)
>>>> + {
>>>> + if (!cp_parser_uncommitted_to_tentative_parse_p (parser))
>>>> + error_at (tilde_loc, "template-id not allowed for destructor");
>>>> + cp_parser_simulate_error (parser);
>>>
>>> The usual pattern is
>>>
>>> if (!cp_parser_simulate_error (parser))
>>> error...
>>
>> Fixed.
>>
>>>> + return error_mark_node;
>>>> + }
>>>> +
>>>> /* If there was an explicit qualification (S::~T), first look
>>>> in the scope given by the qualification (i.e., S).
>>>> @@ -28675,6 +28685,12 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
>>>> if (!constructor_name_p (id, nested_name_specifier))
>>>> constructor_p = false;
>>>> }
>>>> + /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
>>>> + declarator-id of a constructor or destructor. */
>>>> + else if (constructor_p
>>>> + && cxx_dialect >= cxx2a
>>>> + && cp_lexer_next_token_is (parser->lexer, CPP_TEMPLATE_ID))
>>>> + constructor_p = false;
>>>> /* If we still think that this might be a constructor-declarator,
>>>> look for a class-name. */
>>>> else if (constructor_p)
>>>
>>> Do you also want to exclude CPP_TEMPLATE_ID from the test at the top of the
>>> function for C++20?
>>
>> In fact we can get away with only excluding CPP_TEMPLATE_ID in C++20 there,
>> because for e.g. X<T>::X<T>(); we'll give the "names the constructor, not the
>> type" error, so we won't even get here.
>>
>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>
>> -- >8 --
>> This patch implements DR 2237 which says that a simple-template-id is
>> no longer valid as the declarator-id of a constructor or destructor;
>> see [diff.cpp17.class]#2. It is not explicitly stated but out-of-line
>> destructors with a simple-template-id are also meant to be ill-formed
>> now. (Out-of-line constructors like that are invalid since DR1435 I
>> think.) This change only applies to C++20; it is not a DR against C++17.
>>
>> I'm not crazy about the diagnostic in constructors but ISTM that
>> cp_parser_constructor_declarator_p shouldn't print errors.
>>
>> DR 2237
>> * parser.c (cp_parser_unqualified_id): Reject simple-template-id as
>> the declarator-id of a destructor.
>> (cp_parser_constructor_declarator_p): Reject simple-template-id as
>> the declarator-id of a constructor.
>>
>> * g++.dg/DRs/dr2237.C: New test.
>> * g++.dg/parse/constructor2.C: Add dg-error for C++20.
>> * g++.dg/parse/dtor12.C: Likewise.
>> * g++.dg/parse/dtor4.C: Likewise.
>> * g++.dg/template/dtor4.C: Adjust dg-error.
>> * g++.dg/template/error34.C: Likewise.
>> * g++.old-deja/g++.other/inline15.C: Only run for C++17 and lesses.
>> * g++.old-deja/g++.pt/ctor2.C: Add dg-error for C++20.
>> ---
>> gcc/cp/parser.c | 13 ++++++++++++-
>> gcc/testsuite/g++.dg/DRs/dr2237.C | 18 ++++++++++++++++++
>> gcc/testsuite/g++.dg/parse/constructor2.C | 4 ++--
>> gcc/testsuite/g++.dg/parse/dtor12.C | 2 +-
>> gcc/testsuite/g++.dg/parse/dtor4.C | 2 +-
>> gcc/testsuite/g++.dg/template/dtor4.C | 2 +-
>> gcc/testsuite/g++.dg/template/error34.C | 10 +++++-----
>> .../g++.old-deja/g++.other/inline15.C | 2 +-
>> gcc/testsuite/g++.old-deja/g++.pt/ctor2.C | 2 +-
>> 9 files changed, 42 insertions(+), 13 deletions(-)
>> create mode 100644 gcc/testsuite/g++.dg/DRs/dr2237.C
>>
>> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
>> index 591f44f4934..593c45b5888 100644
>> --- a/gcc/cp/parser.c
>> +++ b/gcc/cp/parser.c
>> @@ -6114,6 +6114,15 @@ cp_parser_unqualified_id (cp_parser* parser,
>> return build_min_nt_loc (loc, BIT_NOT_EXPR, make_auto ());
>> }
>>
>> + /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
>> + declarator-id of a constructor or destructor. */
>> + if (token->type == CPP_TEMPLATE_ID && cxx_dialect >= cxx2a)
>> + {
>> + if (!cp_parser_simulate_error (parser))
>> + error_at (tilde_loc, "template-id not allowed for destructor");
>> + return error_mark_node;
>> + }
>> +
>> /* If there was an explicit qualification (S::~T), first look
>> in the scope given by the qualification (i.e., S).
>>
>> @@ -28636,7 +28645,9 @@ cp_parser_constructor_declarator_p (cp_parser *parser, cp_parser_flags flags,
>> if (next_token->type != CPP_NAME
>> && next_token->type != CPP_SCOPE
>> && next_token->type != CPP_NESTED_NAME_SPECIFIER
>> - && next_token->type != CPP_TEMPLATE_ID)
>> + /* DR 2237 (C++20 only): A simple-template-id is no longer valid as the
>> + declarator-id of a constructor or destructor. */
>> + && (next_token->type != CPP_TEMPLATE_ID || cxx_dialect >= cxx2a))
>> return false;
>>
>> /* Parse tentatively; we are going to roll back all of the tokens
>> diff --git a/gcc/testsuite/g++.dg/DRs/dr2237.C b/gcc/testsuite/g++.dg/DRs/dr2237.C
>> new file mode 100644
>> index 00000000000..17abdf179c1
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/DRs/dr2237.C
>> @@ -0,0 +1,18 @@
>> +// DR 2237 - Can a template-id name a constructor?
>> +
>> +template<class T>
>> +struct X {
>> + X<T>(); // { dg-error "expected" "" { target c++2a } }
>> + X(int); // OK, injected-class-name used
>> + ~X<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++2a } }
>> +};
>> +
>> +// ill-formed since DR1435
>> +template<typename T> X<T>::X<T>() {} // { dg-error "names the constructor|as no template constructors" }
>> +template<typename T> X<T>::~X<T>() {} // { dg-error "template-id not allowed for destructor" "" { target c++2a } }
>> +
>> +struct Q {
>> + // ill-formed since DR1435
>> + template<typename T> friend X<T>::X<T>(); // { dg-error "names the constructor|as no template constructors" }
>> + template<typename T> friend X<T>::~X<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++2a } }
>> +};
>> diff --git a/gcc/testsuite/g++.dg/parse/constructor2.C b/gcc/testsuite/g++.dg/parse/constructor2.C
>> index e514e9397e9..87007e9c715 100644
>> --- a/gcc/testsuite/g++.dg/parse/constructor2.C
>> +++ b/gcc/testsuite/g++.dg/parse/constructor2.C
>> @@ -5,7 +5,7 @@ class T
>> {
>> public:
>> T(short,short f=0) {}
>> - T<TClass>(int f) {}
>> - T<TClass>(int f=0,const char* b=0) {}
>> + T<TClass>(int f) {} // { dg-error "expected" "" { target c++2a } }
>> + T<TClass>(int f=0,const char* b=0) {} // { dg-error "expected" "" { target c++2a } }
>> };
>>
>> diff --git a/gcc/testsuite/g++.dg/parse/dtor12.C b/gcc/testsuite/g++.dg/parse/dtor12.C
>> index 1acdfa36b69..d758d3e861d 100644
>> --- a/gcc/testsuite/g++.dg/parse/dtor12.C
>> +++ b/gcc/testsuite/g++.dg/parse/dtor12.C
>> @@ -2,5 +2,5 @@
>>
>> template <class T> class a
>> {
>> - ~a<T>();
>> + ~a<T>(); // { dg-error "template-id not allowed for destructor" "" { target c++2a } }
>> };
>> diff --git a/gcc/testsuite/g++.dg/parse/dtor4.C b/gcc/testsuite/g++.dg/parse/dtor4.C
>> index 729ee2fa130..1059c189eff 100644
>> --- a/gcc/testsuite/g++.dg/parse/dtor4.C
>> +++ b/gcc/testsuite/g++.dg/parse/dtor4.C
>> @@ -7,4 +7,4 @@ template <int N> struct X {
>> };
>>
>> template <int N>
>> -X<N>::~X<N>(){}
>> +X<N>::~X<N>(){} // { dg-error "template-id not allowed for destructor" "" { target c++2a } }
>> diff --git a/gcc/testsuite/g++.dg/template/dtor4.C b/gcc/testsuite/g++.dg/template/dtor4.C
>> index 4f277b248bd..917681fc13e 100644
>> --- a/gcc/testsuite/g++.dg/template/dtor4.C
>> +++ b/gcc/testsuite/g++.dg/template/dtor4.C
>> @@ -5,5 +5,5 @@
>>
>> template<int> struct A
>> {
>> - ~A<0>(); // { dg-error "parse error|declaration" }
>> + ~A<0>(); // { dg-error "parse error|declaration|template-id" }
>> };
>> diff --git a/gcc/testsuite/g++.dg/template/error34.C b/gcc/testsuite/g++.dg/template/error34.C
>> index d0cbcaef28e..ab688d9ba8c 100644
>> --- a/gcc/testsuite/g++.dg/template/error34.C
>> +++ b/gcc/testsuite/g++.dg/template/error34.C
>> @@ -3,27 +3,27 @@
>>
>> template<typename T> struct A
>> {
>> - A<__builtin_offsetof(T, x)>(); // { dg-error "type/value mismatch|offsetof\\(T, x\\)" }
>> + A<__builtin_offsetof(T, x)>(); // { dg-error "type/value mismatch|offsetof\\(T, x\\)|expected" }
>> };
>>
>> template<typename T> struct B
>> {
>> - B<__builtin_offsetof(T, x.y)>(); // { dg-error "type/value mismatch|offsetof\\(T, x.y\\)" }
>> + B<__builtin_offsetof(T, x.y)>(); // { dg-error "type/value mismatch|offsetof\\(T, x.y\\)|expected" }
>> };
>>
>> template<typename T> struct C
>> {
>> - C<__builtin_offsetof(T, x[6])>(); // { dg-error "type/value mismatch|offsetof\\(T, x\\\[6\\\]\\)" }
>> + C<__builtin_offsetof(T, x[6])>(); // { dg-error "type/value mismatch|offsetof\\(T, x\\\[6\\\]\\)|expected" }
>> };
>>
>> template<typename T> struct D
>> {
>> - D<__builtin_offsetof(T, x.y[6].z)>(); // { dg-error "type/value mismatch|offsetof\\(T, x.y\\\[6\\\].z\\)" }
>> + D<__builtin_offsetof(T, x.y[6].z)>(); // { dg-error "type/value mismatch|offsetof\\(T, x.y\\\[6\\\].z\\)|expected" }
>> };
>>
>> struct E { int x; };
>>
>> template<typename T> struct F
>> {
>> - F<__builtin_offsetof(E, x)>(); // { dg-error "type/value mismatch|offsetof\\(E, x\\)" }
>> + F<__builtin_offsetof(E, x)>(); // { dg-error "type/value mismatch|offsetof\\(E, x\\)|expected" }
>> };
>> diff --git a/gcc/testsuite/g++.old-deja/g++.other/inline15.C b/gcc/testsuite/g++.old-deja/g++.other/inline15.C
>> index 43f7f5e3025..a31c60960a5 100644
>> --- a/gcc/testsuite/g++.old-deja/g++.other/inline15.C
>> +++ b/gcc/testsuite/g++.old-deja/g++.other/inline15.C
>> @@ -1,4 +1,4 @@
>> -// { dg-do assemble }
>> +// { dg-do assemble { target c++17_down } }
>> // { dg-options "-O1" }
>> // Origin: Jakub Jelinek <jakub@redhat.com>
>>
>> diff --git a/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C b/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
>> index a8be91ddbb9..4159c84ff56 100644
>> --- a/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
>> +++ b/gcc/testsuite/g++.old-deja/g++.pt/ctor2.C
>> @@ -4,7 +4,7 @@
>>
>> template <class T>
>> struct A {
>> - A<T>();
>> + A<T>(); // { dg-error "expected" "" { target c++2a } }
>> };
>>
>> template <class T>
>>
>> base-commit: 2b2d298ff845ab7a07ffbd51da79473736da3324
>> --
>> Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA
>>
>
> Marek
>
prev parent reply other threads:[~2020-05-20 20:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-04 23:30 Marek Polacek
2020-04-06 1:46 ` Jason Merrill
2020-05-11 20:23 ` Marek Polacek
2020-05-20 18:05 ` Marek Polacek
2020-05-20 20:45 ` Jason Merrill [this message]
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