From: Jason Merrill <jason@redhat.com>
To: gcc-patches@gcc.gnu.org
Subject: [pushed] c++: unique friend shenanigans [PR69836]
Date: Wed, 26 Apr 2023 17:15:47 -0400 [thread overview]
Message-ID: <20230426211547.463435-1-jason@redhat.com> (raw)
Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
Normally we re-instantiate a function declaration when we start to
instantiate the body in case of multiple declarations. In this wacky
testcase, this causes a problem because the type of the w_counter parameter
depends on its declaration not being in scope yet, so the name lookup only
finds the previous declaration. This isn't a problem for member functions,
since they aren't subject to argument-dependent lookup. So let's just skip
the regeneration for hidden friends.
PR c++/69836
gcc/cp/ChangeLog:
* pt.cc (regenerate_decl_from_template): Skip unique friends.
gcc/testsuite/ChangeLog:
* g++.dg/template/friend76.C: New test.
---
gcc/cp/pt.cc | 6 ++++
gcc/testsuite/g++.dg/template/friend76.C | 36 ++++++++++++++++++++++++
2 files changed, 42 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/template/friend76.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 678cb7930e3..e1c272b9817 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -26458,6 +26458,11 @@ regenerate_decl_from_template (tree decl, tree tmpl, tree args)
int args_depth;
int parms_depth;
+ /* Don't bother with this for unique friends that can't be redeclared and
+ might change type if regenerated (PR69836). */
+ if (DECL_UNIQUE_FRIEND_P (decl))
+ goto done;
+
/* Use the source location of the definition. */
DECL_SOURCE_LOCATION (decl) = DECL_SOURCE_LOCATION (tmpl);
@@ -26528,6 +26533,7 @@ regenerate_decl_from_template (tree decl, tree tmpl, tree args)
else
gcc_unreachable ();
+ done:
pop_access_scope (decl);
}
diff --git a/gcc/testsuite/g++.dg/template/friend76.C b/gcc/testsuite/g++.dg/template/friend76.C
new file mode 100644
index 00000000000..ce3ed201dda
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend76.C
@@ -0,0 +1,36 @@
+// PR c++/69836
+// { dg-do compile { target c++11 } }
+
+template<int N = 25> struct number : public number<N - 1> {
+ static constexpr int value = N;
+ static constexpr number<N-1> prev() { return {}; }
+};
+template<> struct number<0> { static constexpr int value = 0; };
+
+template<int N> struct S { enum { value = N }; };
+
+template<int X> constexpr S<X+1> increment(S<X>) { return {}; }
+
+#define RETURN(R) -> decltype(R) { return R; }
+
+#define INIT(TYPE) \
+ using W_ThisType = TYPE; \
+ friend constexpr S<0> state(number<0>, W_ThisType**) { return {}; }
+
+#define STUFF \
+ friend constexpr auto state(number<decltype(state(number<>{}, static_cast<W_ThisType**>(nullptr)))::value+1> w_counter, \
+ W_ThisType **w_this) \
+ RETURN(increment(state(w_counter.prev(), w_this)))
+
+
+template <typename T> struct TemplateObject {
+ INIT(TemplateObject)
+ STUFF
+ STUFF
+};
+
+int main() {
+ TemplateObject<int> t;
+ constexpr auto s = state(number<>{}, static_cast<TemplateObject<int>**>(nullptr)) ;
+ static_assert(s.value == 2, "");
+}
base-commit: 50d866038a910ceb9075b97295a12d77a8d09a3a
prerequisite-patch-id: 4ed1b4e9cbee2ce090bd119cbf47056c35aaeb57
--
2.31.1
reply other threads:[~2023-04-26 21:16 UTC|newest]
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