From 0774240b4df9a9bc48ce33a9625788e402498f5a Mon Sep 17 00:00:00 2001
From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Fri, 29 Mar 2024 13:53:54 +1100
Subject: [PATCH] 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>
---
 gcc/cp/semantics.cc                       |  8 ++++++--
 gcc/testsuite/g++.dg/modules/pr104040_a.C | 14 ++++++++++++++
 gcc/testsuite/g++.dg/modules/pr104040_b.C |  8 ++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/pr104040_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/pr104040_b.C

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index a43ff6e2ab2..329c524a509 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 00000000000..ea36ce0a798
--- /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 00000000000..efe014673fb
--- /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{};
+}