Re: [PATCH] c++: noexcept and copy elision [PR109030]

[Jason Merrill via Gcc-patches]

On 3/6/23 18:59, Marek Polacek wrote:

When processing a noexcept, constructors aren't elided: build_over_call
has
         /* It's unsafe to elide the constructor when handling
            a noexcept-expression, it may evaluate to the wrong
            value (c++/53025).  */
         && (force_elide || cp_noexcept_operand == 0))
so the assert I added recently needs to be relaxed a little bit.

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

        PR c++/109030

gcc/cp/ChangeLog:

        * constexpr.cc (cxx_eval_call_expression): Relax assert.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/noexcept77.C: New test.
---
  gcc/cp/constexpr.cc                     | 6 +++++-
  gcc/testsuite/g++.dg/cpp0x/noexcept77.C | 9 +++++++++
  2 files changed, 14 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept77.C

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 364695b762c..5384d0e8e46 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2869,7 +2869,11 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree 
t,

/* We used to shortcut trivial constructor/op= here, but nowadays

       we can only get a trivial function here with -fno-elide-constructors.  */
-  gcc_checking_assert (!trivial_fn_p (fun) || !flag_elide_constructors);
+  gcc_checking_assert (!trivial_fn_p (fun)
+                      || !flag_elide_constructors
+                      /* We don't elide constructors when processing
+                         a noexcept-expression.  */
+                      || cp_noexcept_operand);

bool non_constant_args = false;

    new_call.bindings
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept77.C 
b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
new file mode 100644
index 00000000000..16db8eb79ee
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept77.C
@@ -0,0 +1,9 @@
+// PR c++/109030
+// { dg-do compile { target c++11 } }
+
+struct foo { };
+
+struct __as_receiver {
+  foo empty_env;
+};
+void sched(foo __fun) noexcept(noexcept(__as_receiver{__fun})) { }

base-commit: dfb14cdd796ad9df6b5f2def047ef36b29385902