OK.
On Mon, Sep 26, 2016 at 8:23 AM, Marek Polacek <pola...@redhat.com> wrote:
> This patch updates __has_cpp_attribute for fallthrough, which is now
> supported.
>
> The system.h hunk should aid people building trunk GCC with older GCC 7 not
> supporting this attribute yet.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2016-09-26 Marek Polacek <pola...@redhat.com>
>
> * c-lex.c (c_common_has_attribute): Handle attribute fallthrough.
>
> * system.h: Use __has_attribute to check whether the fallthrough
> attribute is supported.
>
> * g++.dg/cpp1z/feat-cxx1z.C: Test attribute fallthrough.
>
> diff --git gcc/c-family/c-lex.c gcc/c-family/c-lex.c
> index 829c18b..5c6496e 100644
> --- gcc/c-family/c-lex.c
> +++ gcc/c-family/c-lex.c
> @@ -350,7 +350,8 @@ c_common_has_attribute (cpp_reader *pfile)
> else if (is_attribute_p ("deprecated", attr_name))
> result = 201309;
> else if (is_attribute_p ("maybe_unused", attr_name)
> - || is_attribute_p ("nodiscard", attr_name))
> + || is_attribute_p ("nodiscard", attr_name)
> + || is_attribute_p ("fallthrough", attr_name))
> result = 201603;
> if (result)
> attr_name = NULL_TREE;
> diff --git gcc/system.h gcc/system.h
> index 8ca71cf..0952e4f 100644
> --- gcc/system.h
> +++ gcc/system.h
> @@ -746,8 +746,12 @@ extern void fancy_abort (const char *, int, const char
> *) ATTRIBUTE_NORETURN;
> #define gcc_unreachable() (fancy_abort (__FILE__, __LINE__, __FUNCTION__))
> #endif
>
> -#if GCC_VERSION >= 7000
> -# define gcc_fallthrough() __attribute__((fallthrough))
> +#if GCC_VERSION >= 7000 && defined(__has_attribute)
> +# if __has_attribute(fallthrough)
> +# define gcc_fallthrough() __attribute__((fallthrough))
> +# else
> +# define gcc_fallthrough()
> +# endif
> #else
> # define gcc_fallthrough()
> #endif
> diff --git gcc/testsuite/g++.dg/cpp1z/feat-cxx1z.C
> gcc/testsuite/g++.dg/cpp1z/feat-cxx1z.C
> index 982572e..71c8c7d 100644
> --- gcc/testsuite/g++.dg/cpp1z/feat-cxx1z.C
> +++ gcc/testsuite/g++.dg/cpp1z/feat-cxx1z.C
> @@ -370,6 +370,12 @@
> # error "__has_cpp_attribute(nodiscard) != 201603"
> # endif
>
> +# if ! __has_cpp_attribute(fallthrough)
> +# error "__has_cpp_attribute(fallthrough)"
> +# elif __has_cpp_attribute(fallthrough) != 201603
> +# error "__has_cpp_attribute(fallthrough) != 201603"
> +# endif
> +
> #else
> # error "__has_cpp_attribute"
> #endif
>
> Marek
