Re: [PATCH] c++: explicit inst w/ many constrained partial specs [PR104634]

[Jason Merrill]

On 1/3/24 13:49, Patrick Palka wrote:

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK
for trunk and perhaps 13?

OK for both.

-- >8 --

Here we neglect to emit the definitions of A<double>::f2 and A<double*>::f4
despite the explicit instantiations ultimately because TREE_PUBLIC isn't
set on the corresponding partial specializations, the declarations of which
are created from maybe_new_partial_specialization which is responsible for
disambiguating them from the first and third partial specializations (which
have the same class-head but different constraints).  This makes grokfndecl
in turn clear TREE_PUBLIC for f2 and f4 as if they have internal linkage.

This patch fixes this by setting TREE_PUBLIC appropriately for such partial
specializations.

        PR c++/104634

gcc/cp/ChangeLog:

        * pt.cc (maybe_new_partial_specialization): Propagate TREE_PUBLIC
        to the newly created partial specialization.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/concepts-explicit-inst6.C: New test.
---
  gcc/cp/pt.cc                                  |  1 +
  .../g++.dg/cpp2a/concepts-explicit-inst6.C    | 35 +++++++++++++++++++
  2 files changed, 36 insertions(+)
  create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-explicit-inst6.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index e38e7a773f0..154ac76cb65 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -980,6 +980,7 @@ maybe_new_partial_specialization (tree& type)
        DECL_SOURCE_LOCATION (d) = input_location;
        TREE_PRIVATE (d) = (current_access_specifier == access_private_node);
        TREE_PROTECTED (d) = (current_access_specifier == 
access_protected_node);
+      TREE_PUBLIC (d) = TREE_PUBLIC (DECL_TEMPLATE_RESULT (tmpl));

set_instantiating_module (d);

        DECL_MODULE_EXPORT_P (d) = DECL_MODULE_EXPORT_P (tmpl);
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-explicit-inst6.C 
b/gcc/testsuite/g++.dg/cpp2a/concepts-explicit-inst6.C
new file mode 100644
index 00000000000..4ac0c65c490
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-explicit-inst6.C
@@ -0,0 +1,35 @@
+// PR c++/104634
+// { dg-do compile { target c++20 } }
+// { dg-final { scan-assembler "_ZN1AIiE2f1Ev" } }
+// { dg-final { scan-assembler "_ZN1AIdE2f2Ev" } }
+// { dg-final { scan-assembler "_ZN1AIPiE2f3Ev" } }
+// { dg-final { scan-assembler "_ZN1AIPdE2f4Ev" } }
+
+template<typename T>
+struct A { };
+
+template<class T> requires __is_same(T, int)
+struct A<T> {
+  void f1() { }
+  static inline int m1;
+};
+
+template<class T> requires __is_same(T, double)
+struct A<T> {
+  void f2() { }
+};
+
+template<class T> requires __is_same(T, int)
+struct A<T*> {
+  void f3() { }
+};
+
+template<class T> requires __is_same(T, double)
+struct A<T*> {
+  void f4() { }
+};
+
+template struct A<int>;
+template struct A<double>;
+template struct A<int*>;
+template struct A<double*>;