From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Thu, 8 May 2025 13:06:13 +0000 (+1000)
Subject: c++/modules: Fix handling of -fdeclone-ctor-dtor with explicit instantiations [PR120125]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d787bc4fd372298e9ed5b11cb3050fd3707070f6;p=thirdparty%2Fgcc.git

c++/modules: Fix handling of -fdeclone-ctor-dtor with explicit instantiations [PR120125]

The attached testcase ICEs in maybe_thunk_body because we haven't
created a node in the cgraph for an imported explicit instantiation yet.

We in fact really shouldn't be emitting calls at all, since an imported
explicit instantiation always exists in the TU we imported it from.  So
this patch adjusts DECL_NOT_REALLY_EXTERN handling to account for this.

	PR c++/120125

gcc/cp/ChangeLog:

	* module.cc (trees_out::write_function_def): Only set
	DECL_NOT_REALLY_EXTERN if the importer might need to emit it.
	* optimize.cc (maybe_thunk_body): Don't assume 'fn' has a cgraph
	node created.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/clone-4_a.C: New test.
	* g++.dg/modules/clone-4_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 f562bf8cd91..e7782627a49 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -12638,7 +12638,11 @@ trees_out::write_function_def (tree decl)
     {
       unsigned flags = 0;
 
-      flags |= 1 * DECL_NOT_REALLY_EXTERN (decl);
+      /* Whether the importer should emit this definition, if used.  */
+      flags |= 1 * (DECL_NOT_REALLY_EXTERN (decl)
+		    && (get_importer_interface (decl)
+			!= importer_interface::always_import));
+
       if (f)
 	{
 	  flags |= 2;
diff --git a/gcc/cp/optimize.cc b/gcc/cp/optimize.cc
index 6f9a77f407a..fc4d6c2e351 100644
--- a/gcc/cp/optimize.cc
+++ b/gcc/cp/optimize.cc
@@ -309,8 +309,8 @@ maybe_thunk_body (tree fn, bool force)
       defer_mangling_aliases = save_defer_mangling_aliases;
       cgraph_node::get_create (fns[0])->set_comdat_group (comdat_group);
       cgraph_node::get_create (fns[1])->add_to_same_comdat_group
-	(cgraph_node::get_create (fns[0]));
-      symtab_node::get (fn)->add_to_same_comdat_group
+	(cgraph_node::get (fns[0]));
+      symtab_node::get_create (fn)->add_to_same_comdat_group
 	(symtab_node::get (fns[0]));
       if (fns[2])
 	/* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
diff --git a/gcc/testsuite/g++.dg/modules/clone-4_a.C b/gcc/testsuite/g++.dg/modules/clone-4_a.C
new file mode 100644
index 00000000000..3ee6109f23e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/clone-4_a.C
@@ -0,0 +1,12 @@
+// PR c++/120125
+// { dg-additional-options "-fmodules -fdeclone-ctor-dtor" }
+// { dg-module-cmi M }
+
+export module M;
+
+void foo();
+export template <typename _Tp> struct __shared_ptr {
+  inline __shared_ptr() { foo(); }
+};
+
+template class __shared_ptr<int>;
diff --git a/gcc/testsuite/g++.dg/modules/clone-4_b.C b/gcc/testsuite/g++.dg/modules/clone-4_b.C
new file mode 100644
index 00000000000..1b36cb477c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/clone-4_b.C
@@ -0,0 +1,12 @@
+// PR c++/120125
+// { dg-additional-options "-fmodules -fdeclone-ctor-dtor" }
+
+import M;
+
+int main() {
+  __shared_ptr<int> s1;
+  __shared_ptr<double> s2;
+}
+
+// { dg-final { scan-assembler-not {_ZNW1M12__shared_ptrIiEC[1-4]Ev:} } }
+// { dg-final { scan-assembler {_ZNW1M12__shared_ptrIdEC2Ev:} } }