c++/modules: Ensure vtables are emitted when needed [PR120349]

I missed a testcase in r16-688-gc875748cdc468e for whether a GM vtable
should be emitted in an importer when it has no non-inline key function.
Before that patch the code worked because always we marked all vtables
as DECL_EXTERNAL, which then meant that reading the definition marked
them as DECL_NOT_REALLY_EXTERN.

This patch restores the old behaviour so that vtables are marked
DECL_EXTERNAL (and hence DECL_NOT_REALLY_EXTERN).

	PR c++/120349

gcc/cp/ChangeLog:

	* module.cc (trees_out::core_bools): Always mark vtables as
	DECL_EXTERNAL.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/vtt-3_a.C: New test.
	* g++.dg/modules/vtt-3_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index f728275612eb6607e912df7d06a967734a9e8525..13f8770b7bd1a9edb1269f2ff5c0ce15b20eee9f 100644 (file)
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -5724,9 +5724,13 @@ trees_out::core_bools (tree t, bits_out& bits)
           DECL_NOT_REALLY_EXTERN -> base.not_really_extern
             == that was a lie, it is here  */
 
-       /* decl_flag_1 is DECL_EXTERNAL. Things we emit here, might
-          well be external from the POV of an importer.  */
        bool is_external = t->decl_common.decl_flag_1;
+       /* maybe_emit_vtables relies on vtables being marked as
+          DECL_EXTERNAL and DECL_NOT_REALLY_EXTERN before processing.  */
+       if (!is_external && VAR_P (t) && DECL_VTABLE_OR_VTT_P (t))
+         is_external = true;
+       /* Things we emit here might well be external from the POV of an
+          importer.  */
        if (!is_external
            && VAR_OR_FUNCTION_DECL_P (t)
            && get_importer_interface (t) == importer_interface::external)

diff --git a/gcc/testsuite/g++.dg/modules/vtt-3_a.C b/gcc/testsuite/g++.dg/modules/vtt-3_a.C
new file mode 100644 (file)
index 0000000..f38f024
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/vtt-3_a.C
@@ -0,0 +1,29 @@
+// PR c++/120349
+// { dg-additional-options "-fmodules -Wno-global-module" }
+// { dg-module-cmi M }
+
+module;
+
+// GMF types; should have vtables emitted in importers
+struct BGG {
+  virtual inline ~BGG() {}
+};
+struct BGM {
+  virtual inline ~BGM() {}
+};
+struct DGG : BGG {};
+
+export module M;
+
+export using ::DGG;
+
+// Module-local types; should have vtables emitted here
+struct BM {
+  virtual inline ~BM() {}
+};
+export struct DGM : BGM {};  // note: this emits BGM's vtable here too
+export struct DM : BM {};
+
+// { dg-final { scan-assembler-not "_ZTV3BGG:" } }
+// { dg-final { scan-assembler "_ZTV3BGM:" } }
+// { dg-final { scan-assembler "_ZTVW1M2BM:" } }

diff --git a/gcc/testsuite/g++.dg/modules/vtt-3_b.C b/gcc/testsuite/g++.dg/modules/vtt-3_b.C
new file mode 100644 (file)
index 0000000..ef7ae6c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/vtt-3_b.C
@@ -0,0 +1,14 @@
+// PR c++/120349
+// { dg-additional-options "-fmodules -Wno-global-module" }
+
+import M;
+
+int main() {
+  DGG dgg;
+  DGM dgm;
+  DM dm;
+}
+
+// { dg-final { scan-assembler "_ZTV3BGG:" } }
+// { dg-final { scan-assembler "_ZTV3BGM:" } }
+// { dg-final { scan-assembler-not "_ZTVW1M2BM:" } }