On 8/11/23 09:54, Patrick Palka wrote:
On Thu, 10 Aug 2023, Jason Merrill wrote:
On 8/10/23 16:40, Patrick Palka wrote:
On Thu, 10 Aug 2023, Jason Merrill wrote:
On 8/10/23 12:09, Patrick Palka wrote:
Booststrapped and regtested on x86_64-pc-linux-gnu, does this look OK
for
trunk and perhaps 13?
-- >8 --
We shouldn't issue a "declared static but never defined" warning
for a deduction guide (declared in an anonymous namespace).
PR c++/106604
gcc/cp/ChangeLog:
* decl.cc (wrapup_namespace_globals): Don't issue a
-Wunused-function warning for a deduction guide.
Maybe instead of special casing this here we could set DECL_INITIAL on
deduction guides so they look defined?
That seems to work, but it requires some tweaks in duplicate_decls to keep
saying "declared" instead of "defined" when diagnosing a deduction guide
redeclaration. I'm not sure which approach is preferable?
I'm not sure it matters which we say; the restriction that you can't repeat a
deduction guide makes it more like a definition anyway (even if [basic.def]
disagrees). Is the diagnostic worse apart from that word?
Ah, makes sense. So we can also remove the special case for them in the
redeclaration checking code after we give them a dummy DECL_INITIAL.
Like so?
OK, thanks.
Here's a before/after for the diagnostic with the below patch:
Before
src/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C:11:1: error: deduction guide
‘S()-> S<int>’ redeclared
11 | S() -> S<int>; // { dg-error "redefinition" }
| ^
src/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C:10:1: note: ‘S()-> S<int>’
previously declared here
10 | S() -> S<int>; // { dg-message "previously defined here|old
declaration" }
| ^
After
src/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C:11:1: error: redefinition of
‘S()-> S<int>’
11 | S() -> S<int>; // { dg-error "redefinition" }
| ^
src/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C:10:1: note: ‘S()-> S<int>’
previously defined here
10 | S() -> S<int>; // { dg-message "previously defined here|old
declaration" }
| ^
-- >8 --
Subject: [PATCH] c++: bogus warning w/ deduction guide in anon ns [PR106604]
Here we're unintentionally issuing a "declared static but never defined"
warning for a deduction guide declared in an anonymous namespace.
This patch fixes this by giving deduction guides a dummy DECL_INITIAL,
which suppresses the warning and also allows us to simplify redeclaration
checking for them.
Co-authored-by: Jason Merrill <ja...@redhat.com>
PR c++/106604
gcc/cp/ChangeLog:
* decl.cc (redeclaration_error_message): Remove special handling
for deduction guides.
(grokfndecl): Give deduction guides a dummy DECL_INITIAL.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/class-deduction74.C: Expect "defined" instead
of "declared" in diagnostics for a repeated deduction guide.
* g++.dg/cpp1z/class-deduction116.C: New test.
---
gcc/cp/decl.cc | 14 ++++++--------
gcc/testsuite/g++.dg/cpp1z/class-deduction116.C | 8 ++++++++
gcc/testsuite/g++.dg/cpp1z/class-deduction74.C | 14 +++++++-------
3 files changed, 21 insertions(+), 15 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction116.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 792ab330dd0..3ada5516c58 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -3297,10 +3297,6 @@ redeclaration_error_message (tree newdecl, tree olddecl)
}
}
- if (deduction_guide_p (olddecl)
- && deduction_guide_p (newdecl))
- return G_("deduction guide %q+D redeclared");
-
/* [class.compare.default]: A definition of a comparison operator as
defaulted that appears in a class shall be the first declaration of
that function. */
@@ -3355,10 +3351,6 @@ redeclaration_error_message (tree newdecl, tree olddecl)
}
}
- if (deduction_guide_p (olddecl)
- && deduction_guide_p (newdecl))
- return G_("deduction guide %q+D redeclared");
-
/* Core issue #226 (C++11):
If a friend function template declaration specifies a
@@ -10352,6 +10344,12 @@ grokfndecl (tree ctype,
DECL_CXX_DESTRUCTOR_P (decl) = 1;
DECL_NAME (decl) = dtor_identifier;
break;
+ case sfk_deduction_guide:
+ /* Give deduction guides a definition even though they don't really
+ have one: the restriction that you can't repeat a deduction guide
+ makes them more like a definition anyway. */
+ DECL_INITIAL (decl) = void_node;
+ break;
default:
break;
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction116.C
b/gcc/testsuite/g++.dg/cpp1z/class-deduction116.C
new file mode 100644
index 00000000000..00f6d5fef41
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction116.C
@@ -0,0 +1,8 @@
+// PR c++/106604
+// { dg-do compile { target c++17 } }
+// { dg-additional-options "-Wunused-function" }
+
+namespace {
+ template<class T> struct A { A(...); };
+ A(bool) -> A<bool>; // { dg-bogus "never defined" }
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C
b/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C
index fe113819a95..7bab882da7d 100644
--- a/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction74.C
@@ -7,20 +7,20 @@
template<typename> struct S { };
template<typename> struct X { };
-S() -> S<int>; // { dg-message "previously declared here|old declaration" }
-S() -> S<int>; // { dg-error "redeclared" }
+S() -> S<int>; // { dg-message "previously defined here|old declaration" }
+S() -> S<int>; // { dg-error "redefinition" }
X() -> X<int>;
S() -> S<float>; // { dg-error "ambiguating new declaration of" }
-S(bool) -> S<int>; // { dg-message "previously declared here" }
-explicit S(bool) -> S<int>; // { dg-error "redeclared" }
+S(bool) -> S<int>; // { dg-message "previously defined here" }
+explicit S(bool) -> S<int>; // { dg-error "redefinition" }
-explicit S(char) -> S<int>; // { dg-message "previously declared here" }
-S(char) -> S<int>; // { dg-error "redeclared" }
+explicit S(char) -> S<int>; // { dg-message "previously defined here" }
+S(char) -> S<int>; // { dg-error "redefinition" }
template<typename T> S(T, T) -> S<int>; // { dg-message "previously declared here" }
template<typename T> X(T, T) -> X<int>;
-template<typename T> S(T, T) -> S<int>; // { dg-error "redeclared" }
+template<typename T> S(T, T) -> S<int>; // { dg-error "redefinition" }
// OK: Use SFINAE.
template<typename T> S(T) -> S<typename T::foo>;
