signal.c: get rid of heap corruption

* signal.c (rb_sigaltstack_size): double default size to get rid
  of heap corruption by alternate stack overflow in SEGV handler.
  typically happened at fprintf() in control_frame_dump().

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47984 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Thu Oct 16 23:17:40 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* signal.c (rb_sigaltstack_size): double default size to get rid
+	  of heap corruption by alternate stack overflow in SEGV handler.
+	  typically happened at fprintf() in control_frame_dump().
+
 Thu Oct 16 22:43:12 2014  Tanaka Akira  <akr@fsij.org>
 
 	* vm_backtrace.c (id2str): Fix a variable name.

signal.c

@@ -535,7 +535,7 @@ int
 rb_sigaltstack_size(void)
 {
     /* XXX: BSD_vfprintf() uses >1500KiB stack and x86-64 need >5KiB stack. */
-    int size = 8192;
+    int size = 16*1024;
 
 #ifdef MINSIGSTKSZ
     if (size < MINSIGSTKSZ)