[PATCH v14 01/26] c++: Implement __is_const built-in trait

[Jason Merrill]

On 2/28/24 11:26, Ken Matsui wrote:
> This patch implements built-in trait for std::is_const.

OK.

> gcc/cp/ChangeLog:
> 
> 	* cp-trait.def: Define __is_const.
> 	* constraint.cc (diagnose_trait_expr): Handle CPTK_IS_CONST.
> 	* semantics.cc (trait_expr_value): Likewise.
> 	(finish_trait_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/has-builtin-1.C: Test existence of __is_const.
> 	* g++.dg/ext/is_const.C: New test.
> 
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>   gcc/cp/constraint.cc                     |  3 +++
>   gcc/cp/cp-trait.def                      |  1 +
>   gcc/cp/semantics.cc                      |  4 ++++
>   gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 +++
>   gcc/testsuite/g++.dg/ext/is_const.C      | 20 ++++++++++++++++++++
>   5 files changed, 31 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/ext/is_const.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 49de3211d4c..f32a1c78d63 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3767,6 +3767,9 @@ diagnose_trait_expr (tree expr, tree args)
>       case CPTK_IS_CLASS:
>         inform (loc, "  %qT is not a class", t1);
>         break;
> +    case CPTK_IS_CONST:
> +      inform (loc, "  %qT is not a const type", t1);
> +      break;
>       case CPTK_IS_CONSTRUCTIBLE:
>         if (!t2)
>       inform (loc, "  %qT is not default constructible", t1);
> diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> index 394f006f20f..36faed9c0b3 100644
> --- a/gcc/cp/cp-trait.def
> +++ b/gcc/cp/cp-trait.def
> @@ -64,6 +64,7 @@ DEFTRAIT_EXPR (IS_ASSIGNABLE, "__is_assignable", 2)
>   DEFTRAIT_EXPR (IS_BASE_OF, "__is_base_of", 2)
>   DEFTRAIT_EXPR (IS_BOUNDED_ARRAY, "__is_bounded_array", 1)
>   DEFTRAIT_EXPR (IS_CLASS, "__is_class", 1)
> +DEFTRAIT_EXPR (IS_CONST, "__is_const", 1)
>   DEFTRAIT_EXPR (IS_CONSTRUCTIBLE, "__is_constructible", -1)
>   DEFTRAIT_EXPR (IS_CONVERTIBLE, "__is_convertible", 2)
>   DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index 57840176863..0d08900492b 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12446,6 +12446,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
>       case CPTK_IS_CLASS:
>         return NON_UNION_CLASS_TYPE_P (type1);
>   
> +    case CPTK_IS_CONST:
> +      return CP_TYPE_CONST_P (type1);
> +
>       case CPTK_IS_CONSTRUCTIBLE:
>         return is_xible (INIT_EXPR, type1, type2);
>   
> @@ -12688,6 +12691,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>       case CPTK_IS_ARRAY:
>       case CPTK_IS_BOUNDED_ARRAY:
>       case CPTK_IS_CLASS:
> +    case CPTK_IS_CONST:
>       case CPTK_IS_ENUM:
>       case CPTK_IS_FUNCTION:
>       case CPTK_IS_MEMBER_FUNCTION_POINTER:
> diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> index 02b4b4d745d..e3640faeb96 100644
> --- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> +++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> @@ -71,6 +71,9 @@
>   #if !__has_builtin (__is_class)
>   # error "__has_builtin (__is_class) failed"
>   #endif
> +#if !__has_builtin (__is_const)
> +# error "__has_builtin (__is_const) failed"
> +#endif
>   #if !__has_builtin (__is_constructible)
>   # error "__has_builtin (__is_constructible) failed"
>   #endif
> diff --git a/gcc/testsuite/g++.dg/ext/is_const.C b/gcc/testsuite/g++.dg/ext/is_const.C
> new file mode 100644
> index 00000000000..8a0e8df72a9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/is_const.C
> @@ -0,0 +1,20 @@
> +// { dg-do compile { target c++11 } }
> +
> +#define SA(X) static_assert((X),#X)
> +
> +class ClassType { };
> +using cClassType = const ClassType;
> +using vClassType = volatile ClassType;
> +using cvClassType = const volatile ClassType;
> +
> +// Positive tests.
> +SA(__is_const(const int));
> +SA(__is_const(const volatile int));
> +SA(__is_const(cClassType));
> +SA(__is_const(cvClassType));
> +
> +// Negative tests.
> +SA(!__is_const(int));
> +SA(!__is_const(volatile int));
> +SA(!__is_const(ClassType));
> +SA(!__is_const(vClassType));