c++/modules: Ensure all partial specialisations are tracked [PR114947]

Constrained partial specialisations aren't all necessarily tracked on
the instantiation table.  The modules code uses a separate
'partial_specializations' table to track them instead to ensure that
they get walked and emitted when emitting a module, but currently this
does not always happen.

The attached testcase fails in two ways.  First, because the partial
specialisation is just a declaration (and not a definition),
'set_defining_module' never ends up getting called on it and so it never
gets added to the partial specialisation table.  We fix this by ensuring
that when partial specializations are created they always get added, and
so we never miss one. To prevent adding partial specialisations multiple
times we split this out as a new function.

The second way it fails is that when exporting the primary interface for
a module with partitions, we also re-walk the specializations of all
imported partitions to merge them into a single BMI.  So this patch
ensures that after calling 'match_mergeable_specialization' we also
ensure that if the name came from a partition it gets added to the
specialization table so that a dependency is correctly created for it.

	PR c++/114947

gcc/cp/ChangeLog:

	* cp-tree.h (set_defining_module_for_partial_spec): Declare.
	* module.cc (trees_in::decl_value): Track partial specs coming
	from partitions.
	(set_defining_module): Don't track partial specialisations here
	anymore.
	(set_defining_module_for_partial_spec): New function.
	* pt.cc (process_partial_specialization): Call it.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/partial-4_a.C: New test.
	* g++.dg/modules/partial-4_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index ba9e848c177f3947e16174a0a985e62d9470495a..7ae5b876735ce133628fa1b2a08a8c11e89bbb8a 100644 (file)
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7420,6 +7420,7 @@ extern unsigned get_importing_module (tree, bool = false) ATTRIBUTE_PURE;
 /* Where current instance of the decl got declared/defined/instantiated.  */
 extern void set_instantiating_module (tree);
 extern void set_defining_module (tree);
+extern void set_defining_module_for_partial_spec (tree);
 extern void maybe_key_decl (tree ctx, tree decl);
 extern void propagate_defining_module (tree decl, tree orig);
 extern void remove_defining_module (tree decl);

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 520dd710549ed735923b678b15f22428257ca85f..3ca963cb3e964db2adb33950c26329f79792a844 100644 (file)
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -8416,6 +8416,11 @@ trees_in::decl_value ()
          add_mergeable_specialization (!is_type, &spec, decl, spec_flags);
        }
 
+      /* When making a CMI from a partition we're going to need to walk partial
+        specializations again, so make sure they're tracked.  */
+      if (state->is_partition () && (spec_flags & 2))
+       set_defining_module_for_partial_spec (inner);
+
       if (NAMESPACE_SCOPE_P (decl)
          && (mk == MK_named || mk == MK_unique
              || mk == MK_enum || mk == MK_friend_spec)
@@ -19246,13 +19251,22 @@ set_defining_module (tree decl)
              vec_safe_push (class_members, decl);
            }
        }
-      else if (DECL_IMPLICIT_TYPEDEF_P (decl)
-              && CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_TYPE (decl)))
-       /* This is a partial or explicit specialization.  */
-       vec_safe_push (partial_specializations, decl);
     }
 }
 
+/* Also remember DECL if it's a newly declared class template partial
+   specialization, because these are not necessarily added to the
+   instantiation tables.  */
+
+void
+set_defining_module_for_partial_spec (tree decl)
+{
+  if (module_p ()
+      && DECL_IMPLICIT_TYPEDEF_P (decl)
+      && CLASSTYPE_TEMPLATE_SPECIALIZATION (TREE_TYPE (decl)))
+    vec_safe_push (partial_specializations, decl);
+}
+
 void
 set_originating_module (tree decl, bool friend_p ATTRIBUTE_UNUSED)
 {

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a95ce6eb3daece74d4cc03c1f677632bef419681..dfce1b3c35910d8afe19ccde89b9cb11183b2cbc 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -5456,6 +5456,8 @@ process_partial_specialization (tree decl)
   gcc_checking_assert (!TI_PARTIAL_INFO (tinfo));
   TI_PARTIAL_INFO (tinfo) = build_template_info (tmpl, NULL_TREE);
 
+  set_defining_module_for_partial_spec (decl);
+
   for (inst = DECL_TEMPLATE_INSTANTIATIONS (maintmpl); inst;
        inst = TREE_CHAIN (inst))
     {

diff --git a/gcc/testsuite/g++.dg/modules/partial-4_a.C b/gcc/testsuite/g++.dg/modules/partial-4_a.C
new file mode 100644 (file)
index 0000000..e74bb0a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/partial-4_a.C
@@ -0,0 +1,8 @@
+// PR c++/114947
+// { dg-additional-options "-fmodules-ts -std=c++20" }
+// { dg-module-cmi M:part }
+module M:part;
+
+template <typename> struct R {};
+template <typename T> requires false struct R<T> {};
+template <typename T> requires true struct R<T>;

diff --git a/gcc/testsuite/g++.dg/modules/partial-4_b.C b/gcc/testsuite/g++.dg/modules/partial-4_b.C
new file mode 100644 (file)
index 0000000..1c64567
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/partial-4_b.C
@@ -0,0 +1,5 @@
+// PR c++/114947
+// { dg-additional-options "-fmodules-ts -std=c++20" }
+// { dg-module-cmi M }
+export module M;
+import :part;