Use rb_global_variable to avoid problems with GC.compact (#10)

Author: dylanahsmith

ext/stack_frames/frame.c

@@ -72,6 +72,8 @@ DEFINE_FRAME_ACCESSOR(qualified_method_name)
 
 void stack_frame_define(VALUE mStackFrames) {
     cFrame = rb_define_class_under(mStackFrames, "Frame", rb_cObject);
+    rb_global_variable(&cFrame);
+
     rb_define_alloc_func(cFrame, frame_allocate);
     rb_define_method(cFrame, "lineno", frame_lineno, 0);
     rb_define_method(cFrame, "path", frame_path, 0);

ext/stack_frames/stack_frames.c

@@ -2,10 +2,8 @@
 #include "frame.h"
 #include "buffer.h"
 
-VALUE mStackFrames;
-
 void Init_stack_frames() {
-    mStackFrames = rb_define_module("StackFrames");
+    VALUE mStackFrames = rb_define_module("StackFrames");
     stack_buffer_define(mStackFrames);
     stack_frame_define(mStackFrames);
 }