From: Eric Wong <normalperson@...>
Date: 2015-08-18T20:37:37+00:00
Subject: [ruby-core:70449] Re: [ruby-cvs:58774] naruse:r51626 (trunk): * thread_pthread.c (reserve_stack): ensure the memory is really

--- trunk/thread_pthread.c      2015/08/18 11:17:43     51625
+++ trunk/thread_pthread.c      2015/08/18 11:21:50     51626
@@ -686,8 +686,8 @@
        limit -= size;
        if (buf > limit) {
            limit = alloca(buf - limit);
+           limit[0] = 0; /* ensure alloca is called */
            limit -= stack_check_margin;
-           limit[0] = 0;
        }
     }
 }

We can drop the "limit -= stack_check_margin;" line as well, right?
I encountered build segv with CentOS 5 and 6, too.  I'm honestly
not sure how the original r51625 even works on newer machines :x