--- old/src/java.base/share/classes/java/lang/StackFrameInfo.java	2017-12-12 15:35:05.000000000 -0800
+++ new/src/java.base/share/classes/java/lang/StackFrameInfo.java	2017-12-12 15:35:04.000000000 -0800
@@ -32,23 +32,25 @@
 import java.lang.invoke.MethodType;
 
 class StackFrameInfo implements StackFrame {
-    private final byte RETAIN_CLASS_REF = 0x01;
+    private final static byte RETAIN_CLASS_REF = 0x01;
 
     private final static JavaLangInvokeAccess JLIA =
         SharedSecrets.getJavaLangInvokeAccess();
 
     private final byte flags;
-    private final Object memberName;
-    private final short bci;
+    private final Object memberName;    // MemberName initialized by VM
+    private short bci;                  // unsigned 16-bit value set by VM
     private volatile StackTraceElement ste;
 
     /*
-     * Create StackFrameInfo for StackFrameTraverser and LiveStackFrameTraverser
-     * to use
+     * Construct an empty StackFrameInfo object that will be filled by the VM
+     * during stack walking.
+     *
+     * @see StackStreamFactory.AbstractStackWalker#callStackWalk
+     * @see StackStreamFactory.AbstractStackWalker#fetchStackFrames
      */
     StackFrameInfo(StackWalker walker) {
         this.flags = walker.retainClassRef ? RETAIN_CLASS_REF : 0;
-        this.bci = -1;
         this.memberName = JLIA.newMemberName();
     }
 
@@ -93,7 +95,7 @@
         if (isNativeMethod())
             return -1;
 
-        return bci;
+        return bci & 0xffff;
     }
 
     @Override