[gcc r14-7261] c++: explicit inst w/ similar constrained partial specs [PR104634]

[Patrick Palka]

https://gcc.gnu.org/g:47673571b28278d857371167f4b67a04a1b87b59

commit r14-7261-g47673571b28278d857371167f4b67a04a1b87b59
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Jan 15 16:53:28 2024 -0500

    c++: explicit inst w/ similar constrained partial specs [PR104634]
    
    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, whose declarations 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.
    
    Reviewed-by: Jason Merrill <jason@redhat.com>

Diff:
---
 gcc/cp/pt.cc                                       |  1 +
 .../g++.dg/cpp2a/concepts-explicit-inst6.C         | 35 ++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 6900d172806..8d050e81348 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..a3ae1ca14c2
--- /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<class T>
+struct A { };
+
+template<class T> requires __is_same(T, int)
+struct A<T> {
+  void f1() { }
+};
+
+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*>;