[PATCH] c++/modules: fix virtual destructors [PR103499]

[Nathaniel Shead <nathanieloshead@gmail.com>]

I'm not sure if this is just papering over a general issue of clones not being
exported/imported, or if this is just an exception to the general case of
clones being able to be freely regenerated with no other issues.

Alternatively, would it be better to override the DECL_VINDEX of the original
declaration after filling it in for the clones as well? I wasn't able to see
anything depending on the current behaviour (though I didn't look very hard).

Bootstrapped and regtexted on x86_64-pc-linux-gnu.

-- >8 --

Currently, cloned functions are not included in the CMI.  However, for
virtual destructors the clones must have a different DECL_VINDEX from
their base declaration: the former have an INTEGER_CST indicating the
index into the vtable, while the latter indicate the FUNCTION_DECL that
they're overriding.

As such, this patch ensures that DECL_VINDEX is properly passed on for
cloned functions as well to prevent this from causing issues.

	PR c++/103499

gcc/cp/ChangeLog:

	* module.cc (trees_out::decl_node): Write DECL_VINDEX for
	virtual clones.
	(trees_in::tree_node): Read DECL_VINDEX for virtual clones.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr103499_a.C: New test.
	* g++.dg/modules/pr103499_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/module.cc                          |  6 ++++++
 gcc/testsuite/g++.dg/modules/pr103499_a.C | 12 ++++++++++++
 gcc/testsuite/g++.dg/modules/pr103499_b.C |  8 ++++++++
 3 files changed, 26 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/modules/pr103499_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/pr103499_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index c1c8c226bc1..416a7c414cc 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -8648,6 +8648,8 @@ trees_out::decl_node (tree decl, walk_kind ref)
 
       tree_node (target);
       tree_node (DECL_NAME (decl));
+      if (TREE_CODE (decl) == FUNCTION_DECL && DECL_VIRTUAL_P (decl))
+	tree_node (DECL_VINDEX (decl));
       int tag = insert (decl);
       if (streaming_p ())
 	dump (dumper::TREE)
@@ -9869,6 +9871,10 @@ trees_in::tree_node (bool is_use)
 		}
 	  }
 
+	/* A clone might have a different vtable entry.  */
+	if (res && TREE_CODE (res) == FUNCTION_DECL && DECL_VIRTUAL_P (res))
+	  DECL_VINDEX (res) = tree_node ();
+
 	if (!res)
 	  set_overrun ();
 	int tag = insert (res);
diff --git a/gcc/testsuite/g++.dg/modules/pr103499_a.C b/gcc/testsuite/g++.dg/modules/pr103499_a.C
new file mode 100644
index 00000000000..0497c2c5504
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr103499_a.C
@@ -0,0 +1,12 @@
+// PR c++/103499
+// { dg-module-do compile }
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi pr103499 }
+
+export module pr103499;
+
+export struct base {
+  virtual ~base() = default;
+};
+
+export struct derived : base {};
diff --git a/gcc/testsuite/g++.dg/modules/pr103499_b.C b/gcc/testsuite/g++.dg/modules/pr103499_b.C
new file mode 100644
index 00000000000..b7468562ba9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr103499_b.C
@@ -0,0 +1,8 @@
+// PR c++/103499
+// { dg-additional-options "-fmodules-ts" }
+
+import pr103499;
+
+void test(derived* p) {
+  delete p;
+}
-- 
2.42.0