c++: Keep DECL_SAVED_TREE of cdtor instantiations in modules [PR104040]

A template instantiation still needs to have its DECL_SAVED_TREE so that
its definition is emitted into the CMI. This way it can be emitted in
the object file of any importers that use it, in case it doesn't end up
getting emitted in this TU.

This is true even for maybe-in-charge functions, because we don't
currently stream the clones directly but instead regenerate them from
this function.

	PR c++/104040

gcc/cp/ChangeLog:

	* semantics.cc (expand_or_defer_fn_1): Keep DECL_SAVED_TREE for
	all vague linkage cdtors with modules.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr104040_a.C: New test.
	* g++.dg/modules/pr104040_b.C: New test.

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

3 files changed, 28 insertions, 2 deletions

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index a43ff6e..329c524 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -5029,9 +5029,13 @@ expand_or_defer_fn_1 (tree fn)
       /* We don't want to process FN again, so pretend we've written
 	 it out, even though we haven't.  */
       TREE_ASM_WRITTEN (fn) = 1;
-      /* If this is a constexpr function, keep DECL_SAVED_TREE.  */
+      /* If this is a constexpr function we still need the body to be
+	 able to evaluate it.  Similarly, with modules we only stream
+	 the maybe-in-charge cdtor and regenerate the clones from it on
+	 demand, so we also need to keep the body.  Otherwise we don't
+	 need it anymore.  */
       if (!DECL_DECLARED_CONSTEXPR_P (fn)
-	  && !(modules_p () && DECL_DECLARED_INLINE_P (fn)))
+	  && !(modules_p () && vague_linkage_p (fn)))
 	DECL_SAVED_TREE (fn) = NULL_TREE;
       return false;
     }
diff --git a/gcc/testsuite/g++.dg/modules/pr104040_a.C b/gcc/testsuite/g++.dg/modules/pr104040_a.C
new file mode 100644
index 0000000..ea36ce0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr104040_a.C
@@ -0,0 +1,14 @@
+// PR c++/104040
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi test }
+
+export module test;
+
+export template <typename T>
+struct test {
+  ~test() {}
+};
+
+test<bool> use() {
+  return {};
+}
diff --git a/gcc/testsuite/g++.dg/modules/pr104040_b.C b/gcc/testsuite/g++.dg/modules/pr104040_b.C
new file mode 100644
index 0000000..efe01467
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr104040_b.C
@@ -0,0 +1,8 @@
+// PR c++/104040
+// { dg-additional-options "-fmodules-ts" }
+
+import test;
+
+int main() {
+  test<bool> t{};
+}