On Thu, 12 Sep 2024, Jonathan Wakely wrote:
> Tested x86_64-linux. OK for trunk?
>
> -- >8 --
>
> The standard says that std::launder is ill-formed for function pointers
> and cv void pointers, so there's no reason for __builtin_launder to
> accept them. This change allows implementations of std::launder to defer
> to the built-in for error checking, although libstdc++ will continue to
> diagnose it directly for more user-friendly diagnostics.
>
> PR c++/116673
>
> gcc/cp/ChangeLog:
>
> * semantics.cc (finish_builtin_launder): Diagnose function
> pointers and cv void pointers.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp1z/launder10.C: New test.
> ---
> gcc/cp/semantics.cc | 17 +++++++++++++----
> gcc/testsuite/g++.dg/cpp1z/launder10.C | 15 +++++++++++++++
> 2 files changed, 28 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp1z/launder10.C
>
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 63212afafb3..b194b01f865 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -13482,11 +13482,20 @@ finish_builtin_launder (location_t loc, tree arg,
> tsubst_flags_t complain)
> arg = decay_conversion (arg, complain);
> if (error_operand_p (arg))
> return error_mark_node;
> - if (!type_dependent_expression_p (arg)
> - && !TYPE_PTR_P (TREE_TYPE (arg)))
> + if (!type_dependent_expression_p (arg))
> {
> - error_at (loc, "non-pointer argument to %<__builtin_launder%>");
> - return error_mark_node;
> + tree type = TREE_TYPE (arg);
> + if (!TYPE_PTR_P (type))
> + {
> + error_at (loc, "non-pointer argument to %<__builtin_launder%>");
Do we care about making this builtin SFINAE-friendly by guarding these
errors with tf_error?
> + return error_mark_node;
> + }
> + else if (!object_type_p (TREE_TYPE (type)))
> + {
> + // std::launder is ill-formed for function and cv void pointers.
> + error_at (loc, "invalid argument to %<__builtin_launder%>");
> + return error_mark_node;
> + }
> }
> if (processing_template_decl)
> arg = orig_arg;
> diff --git a/gcc/testsuite/g++.dg/cpp1z/launder10.C
> b/gcc/testsuite/g++.dg/cpp1z/launder10.C
> new file mode 100644
> index 00000000000..7c15eeb891f
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp1z/launder10.C
> @@ -0,0 +1,15 @@
> +// PR c++/116673
> +// { dg-do compile }
> +
> +void
> +bar (void *p)
> +{
> + __builtin_launder (bar); // { dg-error {invalid argument to
> '__builtin_launder'} }
> + __builtin_launder (p); // { dg-error {invalid argument to
> '__builtin_launder'} }
> + const void* cp = p;
> + __builtin_launder (cp); // { dg-error {invalid argument to
> '__builtin_launder'} }
> + volatile void* vp = p;
> + __builtin_launder (vp); // { dg-error {invalid argument to
> '__builtin_launder'} }
> + const volatile void* cvp = p;
> + __builtin_launder (cvp); // { dg-error {invalid argument to
> '__builtin_launder'} }
> +}
> --
> 2.46.0
>
>
