nobu	2017-04-21 09:11:56 +0900 (Fri, 21 Apr 2017)

  New Revision: 58423

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=58423

  Log:
    Suppress a warning in ruby/win32.h [Fix GH-1591]
    
    Fix a warning in ruby/win32.h which can cause failures with mkmf
    
    The return value is implicit type casted from 'long double' to 'double', currently.
    This causes a gcc warning like this:
    
    ```
    In file included from C:\Ruby24-x64\include\ruby-2.4.0/ruby/defines.h:243:0,
                     from C:\Ruby24-x64\include\ruby-2.4.0/ruby/ruby.h:36,
                     from C:\Ruby24-x64\include\ruby-2.4.0/ruby.h:33,
                     from conftest.c:1:
    C:\Ruby24-x64\include\ruby-2.4.0/ruby/win32.h: In function 'rb_w32_pow':
    C:\Ruby24-x64\include\ruby-2.4.0/ruby/win32.h:786:12: warning: conversion to 'double' from 'long double' may alter its value [-Wfloat-conversion]
         return powl(x, y);
                ^~~~~~~~~~
    ```
    
    This is fixed by the attached explicit type cast.
    
    Moreover when CFLAGS is set to '-Wconversion', it prevents the compiler from
    building. This is the case at the nokogiri gem.
    
    The original issue arose at RubyInstaller2: https://github.com/oneclick/rubyinstaller2/commit/576a0eb70aa9348b366c3ecfe83c67811b7bcb9b

  Modified files:
    trunk/include/ruby/win32.h
Index: include/ruby/win32.h
===================================================================
--- include/ruby/win32.h	(revision 58422)
+++ include/ruby/win32.h	(revision 58423)
@@ -781,7 +781,7 @@ RUBY_SYMBOL_EXPORT_END https://github.com/ruby/ruby/blob/trunk/include/ruby/win32.h#L781
 static inline double
 rb_w32_pow(double x, double y)
 {
-    return powl(x, y);
+    return (double)powl(x, y);
 }
 #elif defined(__MINGW64_VERSION_MAJOR)
 double rb_w32_pow(double x, double y);

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