Ruby 2.1.1 BigDecimal patch backported from https://bugs.ruby-lang.org/issues/9657#note-8 - https://bugs.ruby-lang.org/projects/ruby-trunk/repository/revisions/45015/diff/

patch.diff

Index: ext/bigdecimal/bigdecimal.c
===================================================================
--- ext/bigdecimal/bigdecimal.c	(revision 45014)
+++ ext/bigdecimal/bigdecimal.c	(revision 45015)
@@ -2467,9 +2467,11 @@
 static VALUE
 BigDecimal_initialize(int argc, VALUE *argv, VALUE self)
 {
+    ENTER(1);
     Real *pv = rb_check_typeddata(self, &BigDecimal_data_type);
-    Real *x = BigDecimal_new(argc, argv);
+    Real *x;
 
+    GUARD_OBJ(x, BigDecimal_new(argc, argv));
     if (ToValue(x)) {
 	pv = VpCopy(pv, x);
     }
@@ -2548,7 +2550,10 @@
 static VALUE
 BigDecimal_global_new(int argc, VALUE *argv, VALUE self)
 {
-    Real *pv = BigDecimal_new(argc, argv);
+    ENTER(1);
+    Real *pv;
+
+    GUARD_OBJ(pv, BigDecimal_new(argc, argv));
     if (ToValue(pv)) pv = VpCopy(NULL, pv);
     pv->obj = TypedData_Wrap_Struct(rb_cBigDecimal, &BigDecimal_data_type, pv);
     return pv->obj;

USAGE.md

# 1. Get the source however you like
wget http://ftp.ruby-lang.org/pub/ruby/2.1/ruby-2.1.1.tar.gz
tar xfz ruby-2.1.1.tar.gz
cd ruby-2.1.1

# 2. Apply this patch! This is the interesting part.
curl https://gist.githubusercontent.com/henrik/10880288/raw/fe228cf0524873c992fa5c31b1173537dca76a2c/patch.diff | patch -p0

# 3. Build it however you like
# …
make install