* [PATCH] c++: Disable -Wignored-qualifiers for template args [PR107492]
@ 2022-11-01 17:01 Marek Polacek
2022-11-03 19:22 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Marek Polacek @ 2022-11-01 17:01 UTC (permalink / raw)
To: Jason Merrill, GCC Patches
It seems wrong to issue a -Wignored-qualifiers warning for code like:
static_assert(!is_same_v<void(*)(), const void(*)()>);
because there the qualifier matters. Likewise in template
specialization:
template<typename T> struct S { };
template<> struct S<void(*)()> { };
template<> struct S<const void(*)()> { }; // OK, not a redefinition
I'm of the mind that we should disable the warning for template
arguments, as in the patch below.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
PR c++/107492
gcc/cp/ChangeLog:
* parser.cc (cp_parser_template_type_arg): Suppress -Wignored-qualifiers
warning.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wignored-qualifiers3.C: New test.
---
gcc/cp/parser.cc | 4 ++++
gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C | 12 ++++++++++++
2 files changed, 16 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index e0e3cf3eaf6..54ad4b98ed3 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -24334,6 +24334,10 @@ cp_parser_template_type_arg (cp_parser *parser)
const char *saved_message = parser->type_definition_forbidden_message;
parser->type_definition_forbidden_message
= G_("types may not be defined in template arguments");
+ /* It's wrong to issue a -Wignored-qualifiers warning for
+ static_assert(!is_same_v<void(*)(), const void(*)()>);
+ because there the qualifier matters. */
+ warning_sentinel w (warn_ignored_qualifiers);
r = cp_parser_type_id_1 (parser, CP_PARSER_FLAGS_NONE, true, false, NULL);
parser->type_definition_forbidden_message = saved_message;
if (cxx_dialect >= cxx14 && !flag_concepts && type_uses_auto (r))
diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
new file mode 100644
index 00000000000..5696feaaefe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
@@ -0,0 +1,12 @@
+// PR c++/107492
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-Wignored-qualifiers" }
+
+template<typename T> struct S { };
+template<> struct S<void(*)()> { };
+template<> struct S<const void(*)()> { }; // { dg-bogus "ignored" }
+
+template<typename T, typename U> constexpr bool is_same_v = false;
+template<typename T> constexpr bool is_same_v<T, T> = true;
+
+static_assert( ! is_same_v< void(*)(), const void(*)() >, ""); // { dg-bogus "ignored" }
base-commit: e7310e24b1c0ca67b1bb507c1330b2bf39e59e32
--
2.38.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] c++: Disable -Wignored-qualifiers for template args [PR107492]
2022-11-01 17:01 [PATCH] c++: Disable -Wignored-qualifiers for template args [PR107492] Marek Polacek
@ 2022-11-03 19:22 ` Jason Merrill
2022-11-15 0:33 ` [PATCH v2] " Marek Polacek
0 siblings, 1 reply; 4+ messages in thread
From: Jason Merrill @ 2022-11-03 19:22 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 11/1/22 13:01, Marek Polacek wrote:
> It seems wrong to issue a -Wignored-qualifiers warning for code like:
>
> static_assert(!is_same_v<void(*)(), const void(*)()>);
>
> because there the qualifier matters. Likewise in template
> specialization:
>
> template<typename T> struct S { };
> template<> struct S<void(*)()> { };
> template<> struct S<const void(*)()> { }; // OK, not a redefinition
>
> I'm of the mind that we should disable the warning for template
> arguments, as in the patch below.
Hmm, I'm not sure why we would want to treat template arguments
differently from other type-ids. Maybe only warn if funcdecl_p?
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>
> PR c++/107492
>
> gcc/cp/ChangeLog:
>
> * parser.cc (cp_parser_template_type_arg): Suppress -Wignored-qualifiers
> warning.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/Wignored-qualifiers3.C: New test.
> ---
> gcc/cp/parser.cc | 4 ++++
> gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C | 12 ++++++++++++
> 2 files changed, 16 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
>
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index e0e3cf3eaf6..54ad4b98ed3 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -24334,6 +24334,10 @@ cp_parser_template_type_arg (cp_parser *parser)
> const char *saved_message = parser->type_definition_forbidden_message;
> parser->type_definition_forbidden_message
> = G_("types may not be defined in template arguments");
> + /* It's wrong to issue a -Wignored-qualifiers warning for
> + static_assert(!is_same_v<void(*)(), const void(*)()>);
> + because there the qualifier matters. */
> + warning_sentinel w (warn_ignored_qualifiers);
> r = cp_parser_type_id_1 (parser, CP_PARSER_FLAGS_NONE, true, false, NULL);
> parser->type_definition_forbidden_message = saved_message;
> if (cxx_dialect >= cxx14 && !flag_concepts && type_uses_auto (r))
> diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
> new file mode 100644
> index 00000000000..5696feaaefe
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
> @@ -0,0 +1,12 @@
> +// PR c++/107492
> +// { dg-do compile { target c++14 } }
> +// { dg-additional-options "-Wignored-qualifiers" }
> +
> +template<typename T> struct S { };
> +template<> struct S<void(*)()> { };
> +template<> struct S<const void(*)()> { }; // { dg-bogus "ignored" }
> +
> +template<typename T, typename U> constexpr bool is_same_v = false;
> +template<typename T> constexpr bool is_same_v<T, T> = true;
> +
> +static_assert( ! is_same_v< void(*)(), const void(*)() >, ""); // { dg-bogus "ignored" }
>
> base-commit: e7310e24b1c0ca67b1bb507c1330b2bf39e59e32
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] c++: Disable -Wignored-qualifiers for template args [PR107492]
2022-11-03 19:22 ` Jason Merrill
@ 2022-11-15 0:33 ` Marek Polacek
2022-11-15 22:10 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Marek Polacek @ 2022-11-15 0:33 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
On Thu, Nov 03, 2022 at 03:22:12PM -0400, Jason Merrill wrote:
> On 11/1/22 13:01, Marek Polacek wrote:
> > It seems wrong to issue a -Wignored-qualifiers warning for code like:
> >
> > static_assert(!is_same_v<void(*)(), const void(*)()>);
> >
> > because there the qualifier matters. Likewise in template
> > specialization:
> >
> > template<typename T> struct S { };
> > template<> struct S<void(*)()> { };
> > template<> struct S<const void(*)()> { }; // OK, not a redefinition
> >
> > I'm of the mind that we should disable the warning for template
> > arguments, as in the patch below.
>
> Hmm, I'm not sure why we would want to treat template arguments differently
> from other type-ids. Maybe only warn if funcdecl_p?
I think that makes sense. There are other contexts in which cv-quals
matter, for instance trailing-return-type. Updated patch below, plus
I've extended the testcase. Thanks,
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
It seems wrong to issue a -Wignored-qualifiers warning for code like:
static_assert(!is_same_v<void(*)(), const void(*)()>);
because there the qualifier matters. Likewise in template
specialization:
template<typename T> struct S { };
template<> struct S<void(*)()> { };
template<> struct S<const void(*)()> { }; // OK, not a redefinition
And likewise in other type-id contexts such as trailing-return-type:
auto g() -> const void (*)();
This patch limits the warning to the function declaration context only.
PR c++/107492
gcc/cp/ChangeLog:
* decl.cc (grokdeclarator): Only emit a -Wignored-qualifiers warning
when funcdecl_p.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wignored-qualifiers3.C: New test.
---
gcc/cp/decl.cc | 6 ++++-
.../g++.dg/warn/Wignored-qualifiers3.C | 24 +++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 890cfcabd35..67b9f24d7d6 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -13038,7 +13038,11 @@ grokdeclarator (const cp_declarator *declarator,
if (type_quals != TYPE_UNQUALIFIED)
{
- if (SCALAR_TYPE_P (type) || VOID_TYPE_P (type))
+ /* It's wrong, for instance, to issue a -Wignored-qualifiers
+ warning for
+ static_assert(!is_same_v<void(*)(), const void(*)()>);
+ because there the qualifier matters. */
+ if (funcdecl_p && (SCALAR_TYPE_P (type) || VOID_TYPE_P (type)))
warning_at (typespec_loc, OPT_Wignored_qualifiers, "type "
"qualifiers ignored on function return type");
/* [dcl.fct] "A volatile-qualified return type is
diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
new file mode 100644
index 00000000000..dedb38fc995
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
@@ -0,0 +1,24 @@
+// PR c++/107492
+// { dg-do compile { target c++14 } }
+// { dg-additional-options "-Wignored-qualifiers" }
+
+// Here the 'const' matters, so don't warn.
+template<typename T> struct S { };
+template<> struct S<void(*)()> { };
+template<> struct S<const void(*)()> { }; // { dg-bogus "ignored" }
+
+template<typename T, typename U> constexpr bool is_same_v = false;
+template<typename T> constexpr bool is_same_v<T, T> = true;
+
+static_assert( ! is_same_v< void(*)(), const void(*)() >, ""); // { dg-bogus "ignored" }
+
+// Here the 'const' matters as well -> don't warn.
+auto g() -> const void (*)(); // { dg-bogus "ignored" }
+auto g() -> const void (*)() { return nullptr; } // { dg-bogus "ignored" }
+
+// Here as well.
+const void (*h)() = static_cast<const void (*)()>(h); // { dg-bogus "ignored" }
+
+// But let's keep the warning here.
+const void f(); // { dg-warning "ignored" }
+const void f() { } // { dg-warning "ignored" }
base-commit: c41bbfcaf9d6ef5b57a7e89bba70b861c08a686b
--
2.38.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] c++: Disable -Wignored-qualifiers for template args [PR107492]
2022-11-15 0:33 ` [PATCH v2] " Marek Polacek
@ 2022-11-15 22:10 ` Jason Merrill
0 siblings, 0 replies; 4+ messages in thread
From: Jason Merrill @ 2022-11-15 22:10 UTC (permalink / raw)
To: Marek Polacek; +Cc: GCC Patches
On 11/14/22 14:33, Marek Polacek wrote:
> On Thu, Nov 03, 2022 at 03:22:12PM -0400, Jason Merrill wrote:
>> On 11/1/22 13:01, Marek Polacek wrote:
>>> It seems wrong to issue a -Wignored-qualifiers warning for code like:
>>>
>>> static_assert(!is_same_v<void(*)(), const void(*)()>);
>>>
>>> because there the qualifier matters. Likewise in template
>>> specialization:
>>>
>>> template<typename T> struct S { };
>>> template<> struct S<void(*)()> { };
>>> template<> struct S<const void(*)()> { }; // OK, not a redefinition
>>>
>>> I'm of the mind that we should disable the warning for template
>>> arguments, as in the patch below.
>>
>> Hmm, I'm not sure why we would want to treat template arguments differently
>> from other type-ids. Maybe only warn if funcdecl_p?
>
> I think that makes sense. There are other contexts in which cv-quals
> matter, for instance trailing-return-type.
Well, technically they matter in all contexts, including function
declaration:
const void f();
template <class T, class U> struct same;
template <class T> struct same<T,T>{};
same<decltype(f),const void()> s;
but much more likely to be a confused user in that case, whereas in a
template context it's likely to be some deep magic. :)
> Updated patch below, plus I've extended the testcase. Thanks,
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
OK.
> -- >8 --
> It seems wrong to issue a -Wignored-qualifiers warning for code like:
>
> static_assert(!is_same_v<void(*)(), const void(*)()>);
>
> because there the qualifier matters. Likewise in template
> specialization:
>
> template<typename T> struct S { };
> template<> struct S<void(*)()> { };
> template<> struct S<const void(*)()> { }; // OK, not a redefinition
>
> And likewise in other type-id contexts such as trailing-return-type:
>
> auto g() -> const void (*)();
>
> This patch limits the warning to the function declaration context only.
>
> PR c++/107492
>
> gcc/cp/ChangeLog:
>
> * decl.cc (grokdeclarator): Only emit a -Wignored-qualifiers warning
> when funcdecl_p.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/warn/Wignored-qualifiers3.C: New test.
> ---
> gcc/cp/decl.cc | 6 ++++-
> .../g++.dg/warn/Wignored-qualifiers3.C | 24 +++++++++++++++++++
> 2 files changed, 29 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
>
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 890cfcabd35..67b9f24d7d6 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -13038,7 +13038,11 @@ grokdeclarator (const cp_declarator *declarator,
>
> if (type_quals != TYPE_UNQUALIFIED)
> {
> - if (SCALAR_TYPE_P (type) || VOID_TYPE_P (type))
> + /* It's wrong, for instance, to issue a -Wignored-qualifiers
> + warning for
> + static_assert(!is_same_v<void(*)(), const void(*)()>);
> + because there the qualifier matters. */
> + if (funcdecl_p && (SCALAR_TYPE_P (type) || VOID_TYPE_P (type)))
> warning_at (typespec_loc, OPT_Wignored_qualifiers, "type "
> "qualifiers ignored on function return type");
> /* [dcl.fct] "A volatile-qualified return type is
> diff --git a/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
> new file mode 100644
> index 00000000000..dedb38fc995
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/warn/Wignored-qualifiers3.C
> @@ -0,0 +1,24 @@
> +// PR c++/107492
> +// { dg-do compile { target c++14 } }
> +// { dg-additional-options "-Wignored-qualifiers" }
> +
> +// Here the 'const' matters, so don't warn.
> +template<typename T> struct S { };
> +template<> struct S<void(*)()> { };
> +template<> struct S<const void(*)()> { }; // { dg-bogus "ignored" }
> +
> +template<typename T, typename U> constexpr bool is_same_v = false;
> +template<typename T> constexpr bool is_same_v<T, T> = true;
> +
> +static_assert( ! is_same_v< void(*)(), const void(*)() >, ""); // { dg-bogus "ignored" }
> +
> +// Here the 'const' matters as well -> don't warn.
> +auto g() -> const void (*)(); // { dg-bogus "ignored" }
> +auto g() -> const void (*)() { return nullptr; } // { dg-bogus "ignored" }
> +
> +// Here as well.
> +const void (*h)() = static_cast<const void (*)()>(h); // { dg-bogus "ignored" }
> +
> +// But let's keep the warning here.
> +const void f(); // { dg-warning "ignored" }
> +const void f() { } // { dg-warning "ignored" }
>
> base-commit: c41bbfcaf9d6ef5b57a7e89bba70b861c08a686b
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2022-11-01 17:01 [PATCH] c++: Disable -Wignored-qualifiers for template args [PR107492] Marek Polacek
2022-11-03 19:22 ` Jason Merrill
2022-11-15 0:33 ` [PATCH v2] " Marek Polacek
2022-11-15 22:10 ` Jason Merrill
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