eval_error.c: Fix compile error on Solaris 10

* eval_error.c (write_warn, write_warn2, write_warn_str): Fix compile
  error "operands have incompatible types" with Oracle Solaris Studio
  12.4 on Solaris 10.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61324 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

eval_error.c

@@ -6,7 +6,7 @@
 #ifdef HAVE_BUILTIN___BUILTIN_CONSTANT_P
 #define write_warn(str, x) RB_GNUC_EXTENSION_BLOCK( \
         NIL_P(str) ? \
-            warn_print(x) : ( \
+            warn_print(x) : (void)( \
             (__builtin_constant_p(x)) ? 		\
                 rb_str_concat((str), rb_str_new((x), (long)strlen(x))) : \
                 rb_str_concat((str), rb_str_new2(x)) \
@@ -18,14 +18,14 @@
 	rb_write_error(x)			\
 )
 #else
-#define write_warn(str, x) NIL_P(str) ? rb_write_error((x)) : rb_str_concat((str), rb_str_new2(x))
+#define write_warn(str, x) NIL_P(str) ? rb_write_error((x)) : (void)rb_str_concat((str), rb_str_new2(x))
 #define warn_print(x) rb_write_error(x)
 #endif
 
-#define write_warn2(str,x,l) NIL_P(str) ? warn_print2(x,l) : rb_str_concat((str), rb_str_new((x),(l)))
+#define write_warn2(str,x,l) NIL_P(str) ? warn_print2(x,l) : (void)rb_str_concat((str), rb_str_new((x),(l)))
 #define warn_print2(x,l) rb_write_error2((x),(l))
 
-#define write_warn_str(str,x) NIL_P(str) ? rb_write_error_str(x) : rb_str_concat((str), (x))
+#define write_warn_str(str,x) NIL_P(str) ? rb_write_error_str(x) : (void)rb_str_concat((str), (x))
 #define warn_print_str(x) rb_write_error_str(x)
 
 static VALUE error_pos_str(void);