From b192e2007e1c98b548f4aa878523b485968d24a4 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Sun, 4 Jun 2023 12:00:55 -0400 Subject: [PATCH] c++: NRV and goto [PR92407] Here our named return value optimization was breaking the required destructor when the goto takes 'a' out of scope. The simplest fix is to disable the optimization in the presence of user labels. We could do better by disabling the optimization only if there is a backward goto across the variable declaration, but we don't currently track that. PR c++/92407 gcc/cp/ChangeLog: * typeck.cc (check_return_expr): Prevent NRV in the presence of named labels. gcc/testsuite/ChangeLog: * g++.dg/opt/nrv22.C: New test. --- gcc/cp/typeck.cc | 3 +++ gcc/testsuite/g++.dg/opt/nrv22.C | 30 ++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) create mode 100644 gcc/testsuite/g++.dg/opt/nrv22.C diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc index 11fcc7fcd3b3..6618c6a20218 100644 --- a/gcc/cp/typeck.cc +++ b/gcc/cp/typeck.cc @@ -11155,6 +11155,9 @@ check_return_expr (tree retval, bool *no_warning) if (fn_returns_value_p && flag_elide_constructors) { if (named_return_value_okay_p + /* The current NRV implementation breaks if a backward goto needs to + destroy the object (PR92407). */ + && !cp_function_chain->x_named_labels && (current_function_return_value == NULL_TREE || current_function_return_value == bare_retval)) current_function_return_value = bare_retval; diff --git a/gcc/testsuite/g++.dg/opt/nrv22.C b/gcc/testsuite/g++.dg/opt/nrv22.C new file mode 100644 index 000000000000..eb889fa615b1 --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/nrv22.C @@ -0,0 +1,30 @@ +// PR c++/92407 +// { dg-do run } + +struct A +{ + A () { a++; } + A (const A &) { a++; } + ~A () { a--; } + static int a; +}; +int A::a = 0; + +A +foo () +{ + int cnt = 10; +lab: + A a; + if (cnt--) + goto lab; + return a; +} + +int +main () +{ + foo (); + if (A::a) + __builtin_abort (); +} -- 2.47.2