shyouhei	2018-06-05 15:50:20 +0900 (Tue, 05 Jun 2018)

  New Revision: 63571

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=63571

  Log:
    `int isnan(double)` is a POSIXism
    
    - `isnan` is something relatively new.  We need to provide one for
      those systems without it.  However:
    - X/Open defines `int isnan(double)`. Note the `int`.
    - C99 defines `isnan(x)` to be a macro.
    - C++11 nukes them all, undefines all the "masking macro"s, and
      defines its own `bool isnan(double)`.  Note the `bool`.
    - In C++, `int isnan(double)` and `bool isnan(double)` are
      incompatible.
    - So the mess.
    
    [Bug #14816][ruby-core:87364]
    further reading: https://developers.redhat.com/blog/2016/02/29/why-cstdlib-is-more-complicated-than-you-might-think/

  Modified files:
    trunk/include/ruby/missing.h
Index: include/ruby/missing.h
===================================================================
--- include/ruby/missing.h	(revision 63570)
+++ include/ruby/missing.h	(revision 63571)
@@ -168,6 +168,8 @@ RUBY_EXTERN const union bytesequence4_or https://github.com/ruby/ruby/blob/trunk/include/ruby/missing.h#L168
 #    include <ieeefp.h>
 #    endif
 #  define isinf(x) (!finite(x) && !isnan(x))
+#  elif __cplusplus >= 201103L
+#    include <cmath> // it must include constexpr bool isinf(double);
 #  else
 RUBY_EXTERN int isinf(double);
 #  endif
@@ -176,7 +178,11 @@ RUBY_EXTERN int isinf(double); https://github.com/ruby/ruby/blob/trunk/include/ruby/missing.h#L178
 
 #ifndef isnan
 # ifndef HAVE_ISNAN
+#  if __cplusplus >= 201103L
+#    include <cmath> // it must include constexpr bool isnan(double);
+#  else
 RUBY_EXTERN int isnan(double);
+#  endif
 # endif
 #endif
 

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