c++/modules: Support decloned cdtors

When compiling with '-fdeclone-ctor-dtor' (enabled by default with -Os),
we run into issues where we don't correctly emit the underlying
functions.  We also need to ensure that COMDAT constructors are marked
as such before 'maybe_clone_body' attempts to propagate COMDAT groups to
the new thunks.

gcc/cp/ChangeLog:

	* module.cc (post_load_processing): Mark COMDAT as needed, emit
	declarations if maybe_clone_body fails.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/clone-2_a.C: New test.
	* g++.dg/modules/clone-2_b.C: New test.
	* g++.dg/modules/clone-3_a.C: New test.
	* g++.dg/modules/clone-3_b.C: New test.

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

1 files changed, 16 insertions, 4 deletions

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index d7494cc..90ad67d 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -17959,10 +17959,22 @@ post_load_processing ()
       dump () && dump ("Post-load processing of %N", decl);
 
       gcc_checking_assert (DECL_MAYBE_IN_CHARGE_CDTOR_P (decl));
-      /* Cloning can cause loading -- specifically operator delete for
-	 the deleting dtor.  */
-      if (!TREE_ASM_WRITTEN (decl) && maybe_clone_body (decl))
-	TREE_ASM_WRITTEN (decl) = 1;
+
+      if (DECL_COMDAT (decl))
+	comdat_linkage (decl);
+      if (!TREE_ASM_WRITTEN (decl))
+	{
+	  /* Cloning can cause loading -- specifically operator delete for
+	     the deleting dtor.  */
+	  if (maybe_clone_body (decl))
+	    TREE_ASM_WRITTEN (decl) = 1;
+	  else
+	    {
+	      /* We didn't clone the cdtor, make sure we emit it.  */
+	      note_vague_linkage_fn (decl);
+	      cgraph_node::finalize_function (decl, true);
+	    }
+	}
     }
 
   cfun = old_cfun;