Merge pull request #705 from asger-semmle/loop-index-concurrent-modification

Approved by mc-semmle, xiemaisi

javascript/ql/test/query-tests/Statements/LoopIterationSkippedDueToShifting/LoopIterationSkippedDueToShifting.expected

@@ -0,0 +1,3 @@
+| tst.js:4:27:4:44 | parts.splice(i, 1) | Removing an array item without adjusting the loop index 'i' causes the subsequent array item to be skipped. |
+| tst.js:13:29:13:46 | parts.splice(i, 1) | Removing an array item without adjusting the loop index 'i' causes the subsequent array item to be skipped. |
+| tst.js:24:9:24:26 | parts.splice(i, 1) | Removing an array item without adjusting the loop index 'i' causes the subsequent array item to be skipped. |

javascript/ql/test/query-tests/Statements/LoopIterationSkippedDueToShifting/LoopIterationSkippedDueToShifting.qlref

@@ -0,0 +1 @@
+Statements/LoopIterationSkippedDueToShifting.ql

javascript/ql/test/query-tests/Statements/LoopIterationSkippedDueToShifting/tst.js

@@ -0,0 +1,123 @@
+function removeX(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === 'X') parts.splice(i, 1); // NOT OK
+  }
+  return parts.join('/');
+}
+
+function removeXInnerLoop(string, n) {
+  let parts = string.split('/');
+  for (let j = 0; j < n; ++j) {
+    for (let i = 0; i < parts.length; ++i) {
+      if (parts[i] === 'X') parts.splice(i, 1); // NOT OK
+    }
+  }
+  return parts.join('/');
+}
+
+function removeXOuterLoop(string, n) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    for (let j = 0; j < n; ++j) {
+      if (parts[i] === 'X') {
+        parts.splice(i, 1); // NOT OK
+        break;
+      }
+    }
+  }
+  return parts.join('/');
+}
+
+function decrementAfter(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === 'X') {
+        parts.splice(i, 1); // OK
+        --i;
+    }
+  }
+  return parts.join('/');
+}
+
+function postDecrementArgument(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === 'X') {
+        parts.splice(i--, 1); // OK
+    }
+  }
+  return parts.join('/');
+}
+
+
+function breakAfter(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === 'X') {
+        parts.splice(i, 1); // OK - only removes first occurrence
+        break;
+    }
+  }
+  return parts.join('/');
+}
+
+function insertNewElements(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === 'X') {
+        parts.splice(i, 1, '.'); // OK - no shifting due to insert
+    }
+  }
+  return parts.join('/');
+}
+
+function spliceAfterLoop(string) {
+  let parts = string.split('/');
+  let i = 0;
+  for (; i < parts.length; ++i) {
+    if (parts[i] === 'X') break;
+  }
+  if (parts[i] === 'X') {
+    parts.splice(i, 1); // OK - not inside loop 
+  }
+  return parts.join('/');
+}
+
+function spliceAfterLoopNested(string) {
+  let parts = string.split('/');
+  for (let j = 0; j < parts.length; ++j) {
+    let i = j;
+    for (; i < parts.length; ++i) {
+        if (parts[i] === 'X') break;
+    }
+    parts.splice(i, 1); // OK - not inside 'i' loop
+  }
+  return parts.join('/');
+}
+
+function removeAtSpecificPlace(string, k) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (i === k && parts[i] === 'X') parts.splice(i, 1); // OK - more complex logic
+  }
+  return parts.join('/');
+}
+
+function removeFirstAndLast(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (i === 0 || i === parts.length - 1) parts.splice(i, 1); // OK - out of scope of this query
+  }
+  return parts.join('/');
+}
+
+function inspectNextElement(string) {
+  let parts = string.split('/');
+  for (let i = 0; i < parts.length; ++i) {
+    if (i < parts.length - 1 && parts[i] === parts[i + 1]) {
+      parts.splice(i, 1); // OK - next element has been looked at
+    }
+  }
+  return parts.join('/');
+}