add several __has_something macro

With these macros implemented we can write codes just like we can assume
the compiler being clang.  MSC_VERSION_SINCE is defined to implement
those macros, but turned out to be handy for other places.  The -fdeclspec
compiler flag is necessary for clang to properly handle __has_declspec().

1 files changed, 0 insertions, 2 deletions

diff --git a/bignum.c b/bignum.c
index 4569183e45..370c63c787 100644
--- a/bignum.c
+++ b/bignum.c
@@ -5373,11 +5373,9 @@ rb_integer_float_cmp(VALUE x, VALUE y)
 
 #if SIZEOF_LONG * CHAR_BIT >= DBL_MANT_DIG /* assume FLT_RADIX == 2 */
 COMPILER_WARNING_PUSH
-#ifdef __has_warning
 #if __has_warning("-Wimplicit-int-float-conversion")
 COMPILER_WARNING_IGNORED(-Wimplicit-int-float-conversion)
 #endif
-#endif
 static const double LONG_MAX_as_double = LONG_MAX;
 COMPILER_WARNING_POP
 #endif