[gcc r14-10318] c++: visibility wrt concept-id as targ [PR115283]

[Patrick Palka via Gcc-cvs]

https://gcc.gnu.org/g:9583f781e17d4da881ee64db43af939402331413

commit r14-10318-g9583f781e17d4da881ee64db43af939402331413
Author: Patrick Palka <ppa...@redhat.com>
Date:   Wed Jun 12 20:05:05 2024 -0400

    c++: visibility wrt concept-id as targ [PR115283]
    
    Like with alias templates, it seems we don't maintain visibility flags
    for concepts either, so min_vis_expr_r should ignore them for now.
    Otherwise after r14-6789 we may incorrectly give a function template that
    uses a concept-id in its signature internal linkage.
    
            PR c++/115283
    
    gcc/cp/ChangeLog:
    
            * decl2.cc (min_vis_expr_r) <case TEMPLATE_DECL>: Ignore
            concepts.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/template/linkage5.C: New test.
    
    Reviewed-by: Jason Merrill <ja...@redhat.com>
    (cherry picked from commit b1fe718cbe0c8883af89f52e0aad3ebf913683de)

Diff:
---
 gcc/cp/decl2.cc                          |  5 +++--
 gcc/testsuite/g++.dg/template/linkage5.C | 14 ++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 806a2a4bc69d..88933be732db 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -2710,9 +2710,10 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void 
*data)
       break;
 
     case TEMPLATE_DECL:
-      if (DECL_ALIAS_TEMPLATE_P (t))
+      if (DECL_ALIAS_TEMPLATE_P (t) || standard_concept_p (t))
        /* FIXME: We don't maintain TREE_PUBLIC / DECL_VISIBILITY for
-          alias templates so we can't trust it here (PR107906).  */
+          alias templates so we can't trust it here (PR107906).  Ditto
+          for concepts.  */
        break;
       t = DECL_TEMPLATE_RESULT (t);
       /* Fall through.  */
diff --git a/gcc/testsuite/g++.dg/template/linkage5.C 
b/gcc/testsuite/g++.dg/template/linkage5.C
new file mode 100644
index 000000000000..7e8f93f546f1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/linkage5.C
@@ -0,0 +1,14 @@
+// PR c++/115283
+// { dg-final { scan-assembler "(weak|glob)\[^\n\]*_Z1fIiEv1AIX1CIT_EEE" } }
+// { dg-do compile { target c++20 } }
+
+template<class T>
+concept C = true;
+
+template<bool B>
+struct A { };
+
+template<class T>
+void f(A<C<T>>) { }
+
+template void f<int>(A<true>);