[gcc r13-3236] c++ modules: ICE with templated friend and std namespace [PR100134]

[Patrick Palka <ppalka@gcc.gnu.org>]

https://gcc.gnu.org/g:9736a42e1fb8df30d72cf28594d9046bf50200c1

commit r13-3236-g9736a42e1fb8df30d72cf28594d9046bf50200c1
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Oct 11 15:02:23 2022 -0400

    c++ modules: ICE with templated friend and std namespace [PR100134]
    
    The function depset::hash::add_binding_entity has an assert verifying
    that if a namespace contains an exported entity, then the namespace must
    have been opened in the module purview:
    
      if (data->hash->add_namespace_entities (decl, data->partitions))
        {
          /* It contains an exported thing, so it is exported.  */
          gcc_checking_assert (DECL_MODULE_PURVIEW_P (decl));
          DECL_MODULE_EXPORT_P (decl) = true;
        }
    
    We're tripping over this assert in the below testcase because by
    instantiating and exporting std::A<int>, we in turn define and export the
    hidden friend std::f(A<int>) without ever having opened the enclosing
    namespace std within the module purview, and thus DECL_MODULE_PURVIEW_P
    for std is false.
    
    It's important that the enclosing namespace is std here: if we use
    a different namespace then the ICE disappears.  This probably has
    something to do with us predefining std via push_namespace from
    cxx_init_decl_processing (which makes it look like we've opened it
    within the TU), whereas with another namespace we would instead lazily
    create its NAMESPACE_DECL from add_imported_namespace.
    
    Since templated friend functions are special in that they give us a way
    to introduce a namespace-scope function without having to explicitly
    open the namespace, this patch proposes to fix this ICE by propagating
    DECL_MODULE_PURVIEW_P from the introduced function to the enclosing
    namespace during tsubst_friend_function.
    
            PR c++/100134
    
    gcc/cp/ChangeLog:
    
            * pt.cc (tsubst_friend_function): Propagate DECL_MODULE_PURVIEW_P
            from the introduced namespace-scope function to the namespace.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/tpl-friend-8_a.H: New test.
            * g++.dg/modules/tpl-friend-8_b.C: New test.

Diff:
---
 gcc/cp/pt.cc                                  | 8 ++++++++
 gcc/testsuite/g++.dg/modules/tpl-friend-8_a.H | 9 +++++++++
 gcc/testsuite/g++.dg/modules/tpl-friend-8_b.C | 8 ++++++++
 3 files changed, 25 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 5b9fc588a21..b80e7ff1845 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -11448,6 +11448,14 @@ tsubst_friend_function (tree decl, tree args)
 	     by duplicate_decls.  */
 	  new_friend = old_decl;
 	}
+
+      /* We've just introduced a namespace-scope function in the purview
+	 without necessarily having opened the enclosing namespace, so
+	 make sure the namespace is in the purview now too.  */
+      if (modules_p ()
+	  && DECL_MODULE_PURVIEW_P (STRIP_TEMPLATE (new_friend))
+	  && TREE_CODE (DECL_CONTEXT (new_friend)) == NAMESPACE_DECL)
+	DECL_MODULE_PURVIEW_P (DECL_CONTEXT (new_friend)) = true;
     }
   else
     {
diff --git a/gcc/testsuite/g++.dg/modules/tpl-friend-8_a.H b/gcc/testsuite/g++.dg/modules/tpl-friend-8_a.H
new file mode 100644
index 00000000000..bd2290460b5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/tpl-friend-8_a.H
@@ -0,0 +1,9 @@
+// PR c++/100134
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+namespace std {
+  template<class T> struct A {
+    friend void f(A) { }
+  };
+}
diff --git a/gcc/testsuite/g++.dg/modules/tpl-friend-8_b.C b/gcc/testsuite/g++.dg/modules/tpl-friend-8_b.C
new file mode 100644
index 00000000000..76d7447c2eb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/tpl-friend-8_b.C
@@ -0,0 +1,8 @@
+// PR c++/100134
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi pr100134 }
+export module pr100134;
+
+import "tpl-friend-8_a.H";
+
+export std::A<int> a;