From: Eric Wong <normalperson@...>
Date: 2015-01-07T19:24:20+00:00
Subject: [ruby-core:67399] Re: [ruby-trunk - Bug #10710] can't compile ruby 2.2.0 with gcc versions older than 4.4.0

stkaes@googlemail.com wrote:
> compilation stops because gcc before 4.4.0 does not support the flag
> -Wno-packed-bitfield-compat.

I'm curious what error you saw.  An ancient CentOS 5.4 x86-64 machine
managed to build it using: gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46)

--- a/configure.in
+++ b/configure.in
@@ -788,6 +788,9 @@ rb_cv_warnflags="$warnflags"
 if test "$GCC:${warnflags+set}:no" = yes::no; then
     if test $gcc_major -ge 4; then
 	extra_warning=-Werror=extra-tokens
+        if test $gcc_major -gt 4 -o $gcc_minor -ge 4; then
+            extra_warning="$extra_warning -Wno-packed-bitfield-compat"
+        fi

I think "||" is preferable to "-o" for portability.  But maybe not a
problem nowadays...