On Wed, Apr 06, 2022 at 04:36:49PM -0300, Alexandre Oliva via Gcc-patches wrote:
>
> On targets that return this from cdtors, cxx_eval_call_expression may
> flag flowing off the end of a dtor. That's preempted for ctors, and
> avoided entirely when dtors return void, but when they return this,
> the return value should be conceptually disregarded, without making
> room for such internal ABI details to make a program ill-formed, as in
> g++.dg/cpp2a/constexpr-dtor12.C on arm-eabi.
>
> Regstrapped on x86_64-linux-gnu, also verified the testcase fix on
> arm-eabi. Ok to install?
>
>
> for gcc/cp/ChangeLog
>
> * constexpr.cc (cxx_eval_call_expression): Disregard dtor
> result.
> ---
> gcc/cp/constexpr.cc | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> index 9c40b0515747d..d8bc864ae6bcc 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -2889,7 +2889,8 @@ cxx_eval_call_expression (const constexpr_ctx *ctx,
> tree t,
> else
> {
> result = *ctx->global->values.get (res);
> - if (result == NULL_TREE && !*non_constant_p)
> + if (result == NULL_TREE && !*non_constant_p
> + && !DECL_DESTRUCTOR_P (fun))
Would it make sense to use
&& !(DECL_DESTRUCTOR_P (fun) && targetm.cxx.cdtor_returns_this ())
instead?
> {
> if (!ctx->quiet)
> error ("%<constexpr%> call flows off the end "
Marek
