Merge pull request jruby#8810 from NGRsoftlab/Fix-8809

Possible fix for 8809

Author: headius

core/src/main/java/org/jruby/runtime/ThreadContext.java

@@ -908,7 +908,7 @@ public IRubyObject createCallerBacktrace(int level, int length, Stream<StackWalk
      * @param length the length of the trace
      * @return an Array with the backtrace locations
      */
-    public IRubyObject createCallerLocations(int level, Integer length, Stream<StackWalker.StackFrame> stackStream) {
+    public IRubyObject createCallerLocations(int level, int length, Stream<StackWalker.StackFrame> stackStream) {
         runtime.incrementCallerCount();
 
         RubyStackTraceElement[] fullTrace = getPartialTrace(level, length, stackStream);
@@ -924,7 +924,7 @@ public IRubyObject createCallerLocations(int level, Integer length, Stream<Stack
     }
 
     /**
-     * Like {@link #createCallerLocations(int, Integer, Stream)} but accepts a lambda to yield each location and yields
+     * Like {@link #createCallerLocations(int, int, Stream)} but accepts a lambda to yield each location and yields
      * all stack elements until the loop ends or is broken early.
      *
      * @param stackStream the stream of StackFrame objects from JVM
@@ -934,8 +934,8 @@ public void eachCallerLocation(Stream<StackWalker.StackFrame> stackStream, Consu
         eachPartialTrace(stackStream, (elt) -> consumer.accept(RubyThread.Location.newLocation(runtime, elt)));
     }
 
-    private RubyStackTraceElement[] getPartialTrace(int level, Integer length, Stream<StackWalker.StackFrame> stackStream) {
-        if (length != null && length == 0) return RubyStackTraceElement.EMPTY_ARRAY;
+    private RubyStackTraceElement[] getPartialTrace(int level, int length, Stream<StackWalker.StackFrame> stackStream) {
+        if (length == 0) return RubyStackTraceElement.EMPTY_ARRAY;
         return TraceType.Gather.CALLER.getBacktraceData(this, stackStream).getPartialBacktrace(runtime, level + length);
     }
 
@@ -947,7 +947,7 @@ private RubyStackTraceElement[] getWarnTrace(int level, Stream<StackWalker.Stack
         return TraceType.Gather.WARN.getBacktraceData(this, stackStream).getPartialBacktrace(runtime, level + 1);
     }
 
-    private static int safeLength(int level, Integer length, RubyStackTraceElement[] trace) {
+    private static int safeLength(int level, int length, RubyStackTraceElement[] trace) {
         final int baseLength = trace.length - level;
         return Math.min(length, baseLength);
     }