Re: [PATCH v7 1/6] c++: implement __is_reference built-in trait

[Patrick Palka <ppalka@redhat.com>]

On Mon, 12 Jun 2023, Ken Matsui via Libstdc++ wrote:

> This patch implements built-in trait for std::is_reference.
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-trait.def: Define __is_reference.
> 	* constraint.cc (diagnose_trait_expr): Handle CPTK_IS_REFERENCE.
> 	* semantics.cc (trait_expr_value): Likewise.
> 	(finish_trait_expr): Likewise.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/has-builtin-1.C: Test existence of __is_reference.
> 	* g++.dg/ext/is_reference.C: New test.

LGTM

> 
> Signed-off-by: Ken Matsui <kmatsui@cs.washington.edu>
> ---
>  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_reference.C  | 34 ++++++++++++++++++++++++
>  5 files changed, 45 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/ext/is_reference.C
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 8cf0f2d0974..f6951ee2670 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3705,6 +3705,9 @@ diagnose_trait_expr (tree expr, tree args)
>      case CPTK_HAS_VIRTUAL_DESTRUCTOR:
>        inform (loc, "  %qT does not have a virtual destructor", t1);
>        break;
> +    case CPTK_IS_REFERENCE:
> +      inform (loc, "  %qT is not a reference", t1);
> +      break;
>      case CPTK_IS_ABSTRACT:
>        inform (loc, "  %qT is not an abstract class", t1);
>        break;
> diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> index 8b7fece0cc8..1e3310cd682 100644
> --- a/gcc/cp/cp-trait.def
> +++ b/gcc/cp/cp-trait.def
> @@ -67,6 +67,7 @@ DEFTRAIT_EXPR (IS_CONVERTIBLE, "__is_convertible", 2)
>  DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
>  DEFTRAIT_EXPR (IS_ENUM, "__is_enum", 1)
>  DEFTRAIT_EXPR (IS_FINAL, "__is_final", 1)
> +DEFTRAIT_EXPR (IS_REFERENCE, "__is_reference", 1)
>  DEFTRAIT_EXPR (IS_LAYOUT_COMPATIBLE, "__is_layout_compatible", 2)
>  DEFTRAIT_EXPR (IS_LITERAL_TYPE, "__is_literal_type", 1)
>  DEFTRAIT_EXPR (IS_NOTHROW_ASSIGNABLE, "__is_nothrow_assignable", 2)
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index a2e74a5d2c7..2f37bc353a1 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -12075,6 +12075,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
>      case CPTK_IS_FINAL:
>        return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
>  
> +    case CPTK_IS_REFERENCE:
> +      return type_code1 == REFERENCE_TYPE;
> +
>      case CPTK_IS_LAYOUT_COMPATIBLE:
>        return layout_compatible_type_p (type1, type2);
>  
> @@ -12289,6 +12292,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
>      case CPTK_IS_ENUM:
>      case CPTK_IS_UNION:
>      case CPTK_IS_SAME:
> +    case CPTK_IS_REFERENCE:
>        break;
>  
>      case CPTK_IS_LAYOUT_COMPATIBLE:
> diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> index f343e153e56..b697673790c 100644
> --- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> +++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> @@ -146,3 +146,6 @@
>  #if !__has_builtin (__remove_cvref)
>  # error "__has_builtin (__remove_cvref) failed"
>  #endif
> +#if !__has_builtin (__is_reference)
> +# error "__has_builtin (__is_reference) failed"
> +#endif
> diff --git a/gcc/testsuite/g++.dg/ext/is_reference.C b/gcc/testsuite/g++.dg/ext/is_reference.C
> new file mode 100644
> index 00000000000..b5ce4db7afd
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/ext/is_reference.C
> @@ -0,0 +1,34 @@
> +// { dg-do compile { target c++11 } }
> +
> +#include <testsuite_tr1.h>
> +
> +using namespace __gnu_test;
> +
> +#define SA(X) static_assert((X),#X)
> +#define SA_TEST_CATEGORY(TRAIT, TYPE, EXPECT)	\
> +  SA(TRAIT(TYPE) == EXPECT);					\
> +  SA(TRAIT(const TYPE) == EXPECT);				\
> +  SA(TRAIT(volatile TYPE) == EXPECT);			\
> +  SA(TRAIT(const volatile TYPE) == EXPECT)
> +
> +// Positive tests.
> +SA_TEST_CATEGORY(__is_reference, int&, true);
> +SA_TEST_CATEGORY(__is_reference, ClassType&, true);
> +SA(__is_reference(int(&)(int)));
> +SA_TEST_CATEGORY(__is_reference, int&&, true);
> +SA_TEST_CATEGORY(__is_reference, ClassType&&, true);
> +SA(__is_reference(int(&&)(int)));
> +SA_TEST_CATEGORY(__is_reference, IncompleteClass&, true);
> +
> +// Negative tests
> +SA_TEST_CATEGORY(__is_reference, void, false);
> +SA_TEST_CATEGORY(__is_reference, int*, false);
> +SA_TEST_CATEGORY(__is_reference, int[3], false);
> +SA(!__is_reference(int(int)));
> +SA(!__is_reference(int(*const)(int)));
> +SA(!__is_reference(int(*volatile)(int)));
> +SA(!__is_reference(int(*const volatile)(int)));
> +
> +// Sanity check.
> +SA_TEST_CATEGORY(__is_reference, ClassType, false);
> +SA_TEST_CATEGORY(__is_reference, IncompleteClass, false);
> -- 
> 2.41.0
> 
>