[ruby/fiddle] windows: use GetLastError() for win32_last_error

Ruby: [Bug #11579]

Patch by cremno phobia. Thanks!!!

https://github.com/ruby/fiddle/commit/760a8f9b14

ext/fiddle/function.c

@@ -378,9 +378,10 @@ function_call(int argc, VALUE argv[], VALUE self)
     {
         int errno_keep = errno;
 #if defined(_WIN32)
+        DWORD error = WSAGetLastError();
         int socket_error = WSAGetLastError();
         rb_funcall(mFiddle, rb_intern("win32_last_error="), 1,
-                   INT2NUM(errno_keep));
+                   ULONG2NUM(error));
         rb_funcall(mFiddle, rb_intern("win32_last_socket_error="), 1,
                    INT2NUM(socket_error));
 #endif

test/fiddle/test_function.rb

@@ -9,6 +9,7 @@ module Fiddle
     def setup
       super
       Fiddle.last_error = nil
+      Fiddle.win32_last_error = nil if WINDOWS
     end
 
     def test_default_abi
@@ -94,6 +95,19 @@ module Fiddle
       refute_nil Fiddle.last_error
     end
 
+    if WINDOWS
+      def test_win32_last_error
+        kernel32 = dlopen('kernel32')
+        args = [kernel32['SetLastError'], [TYPE_LONG], TYPE_VOID]
+        args << Function::STDCALL if Function.const_defined?(:STDCALL)
+        set_last_error = Function.new(*args)
+        assert_nil(Fiddle.win32_last_error)
+        n = 1 << 29 | 1
+        set_last_error.call(n)
+        assert_equal(n, Fiddle.win32_last_error)
+      end
+    end
+
     def test_strcpy
       f = Function.new(@libc['strcpy'], [TYPE_VOIDP, TYPE_VOIDP], TYPE_VOIDP)
       buff = +"000"