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 --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 5b9fc588a2127ed2ee4fd93b9d2848dc22b83b91..b80e7ff18455275da21fcefe2fce10169536f917 100644 (file)
--- 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 (file)
index 0000000..bd22904
--- /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 (file)
index 0000000..76d7447
--- /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;