1 files changed, 43 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/debug/Frame-onStep-15.js b/js/src/jit-test/tests/debug/Frame-onStep-15.js
new file mode 100644
index 0000000000..819b0e4b6c
--- /dev/null
+++ b/js/src/jit-test/tests/debug/Frame-onStep-15.js
@@ -0,0 +1,43 @@
+// Test how stepping interacts with for(;;) statements.
+
+let g = newGlobal({newCompartment: true});
+
+// We want a for(;;) loop whose body is evaluated at least once, to
+// see whether the loop head is hit a second time.
+g.eval(`function f() {
+  let x = 0;
+  debugger;                     // +0
+  for(;;) {                     // +1
+    if (x++ == 1) break;        // +2
+  }                             // +3
+  debugger;                     // +4
+}`);
+
+let dbg = Debugger(g);
+
+function test(s, expected) {
+  let result = '';
+
+  dbg.onDebuggerStatement = function(frame) {
+    // On the second debugger statement, we're done.
+    dbg.onDebuggerStatement = function(frame) {
+      frame.onStep = undefined;
+    };
+
+    let debugLine = frame.script.getOffsetLocation(frame.offset).lineNumber;
+    frame.onStep = function() {
+      // Only examine stops at entry points for the line.
+      let lineNo = this.script.getOffsetLocation(this.offset).lineNumber;
+      if (this.script.getLineOffsets(lineNo).indexOf(this.offset) < 0) {
+        return undefined;
+      }
+
+      let delta = this.script.getOffsetLocation(this.offset).lineNumber - debugLine;
+      result += delta;
+    };
+  };
+  g.eval(s);
+  assertEq(result, expected);
+}
+
+test('f()', '2124');