[gcc r13-8249] c++: throwing cleanup after return [PR113347]

[Jason Merrill]

https://gcc.gnu.org/g:713fbaff8b17a01d3b72110f89112851ed43a90a

commit r13-8249-g713fbaff8b17a01d3b72110f89112851ed43a90a
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Jan 23 15:41:09 2024 -0500

    c++: throwing cleanup after return [PR113347]
    
    Here we were assuming that current_retval_sentinel would be set if we have
    seen a throwing cleanup, but that's not the case if the cleanup is after all
    returns.
    
    This change isn't needed on trunk, where current_retval_sentinel is set for
    all NRV functions.
    
            PR c++/113347
    
    gcc/cp/ChangeLog:
    
            * semantics.cc (finalize_nrv_r): Handle null
            current_retval_sentinel.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/eh/return3.C: New test.

Diff:
---
 gcc/cp/semantics.cc               |  3 ++-
 gcc/testsuite/g++.dg/eh/return3.C | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 02838775003..ff5252905fe 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -4953,7 +4953,8 @@ finalize_nrv_r (tree* tp, int* walk_subtrees, void* data)
       /* If a cleanup might throw, we need to clear current_retval_sentinel on
 	 the exception path so an outer cleanup added by
 	 maybe_splice_retval_cleanup doesn't run.  */
-      if (cp_function_chain->throwing_cleanup)
+      if (current_retval_sentinel
+	  && cp_function_chain->throwing_cleanup)
 	{
 	  tree clear = build2 (MODIFY_EXPR, boolean_type_node,
 			       current_retval_sentinel,
diff --git a/gcc/testsuite/g++.dg/eh/return3.C b/gcc/testsuite/g++.dg/eh/return3.C
new file mode 100644
index 00000000000..76aa50d523d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/eh/return3.C
@@ -0,0 +1,17 @@
+// PR c++/113347
+
+#if __cplusplus < 201103L
+#define THROWS
+#else
+#define THROWS noexcept(false)
+#endif
+
+struct A { ~A(); };
+struct B { ~B() THROWS; };
+
+A f()
+{
+  A a;
+  return a;
+  B();
+}