Introduce $262.agent.safeBroadcast and migrate Atomics tests.

Migrating all tests to this API is necessary to prevent tests from hanging indefinitely when a SAB is sent to a worker but the code in the worker attempts to create a non-sharable TypedArray (something that is not Int32Array or BigInt64Array). When that scenario occurs, an exception is thrown and the agent worker can no longer communicate with any other threads that control the SAB. If the main thread happens to be spinning in the $262.agent.waitUntil() while loop, it will never meet its termination condition and the test will hang indefinitely. Because we've defined $262.agent.broadcast(SAB) in https://github.com/tc39/test262/blob/master/INTERPRETING.md, there are host implementations that assume compatibility, which must be maintained.
tc39 · Nov 20, 2018 · e488309 · e488309
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diff --git a/INTERPRETING.md b/INTERPRETING.md
@@ -66,24 +66,24 @@ properties of the global scope prior to test execution.
   - **`global`** - a reference to the global object on which `$262` was initially defined
   - **`IsHTMLDDA`** - (present only in implementations that can provide it) an
     object that 1) has an [[IsHTMLDDA]] internal slot, and 2) when called with
-    no arguments or with the single argument `""` returns `null`.  Use this
+    no arguments or with the single argument `""` returns `null`. Use this
     property to test that ECMAScript algorithms aren't mis-implemented to treat
     `document.all` as being `undefined` or of type Undefined (instead of
-    Object).  (The peculiar second requirement permits testing algorithms when
+    Object). (The peculiar second requirement permits testing algorithms when
     they also call `document.all` with such arguments, so that testing for
-    correct behavior requires knowing how the call behaves.  This is rarely
+    correct behavior requires knowing how the call behaves. This is rarely
     necessary.)  Tests using this function must be tagged with the `IsHTMLDDA`
     feature so that only hosts supporting this property will run them.
   - **`agent`** - an ordinary object with the following properties:
     - **`start`** - a function that takes a script source string and runs
-      the script in a concurrent agent.  Will block until that agent is
-      running.  The agent has no representation.  The agent script will be
+      the script in a concurrent agent. Will block until that agent is
+      running. The agent has no representation. The agent script will be
       run in an environment that has an object `$262` with a property `agent`
       with the following properties:
       - **`receiveBroadcast`** - a function that takes a function and
         calls the function when it has received a broadcast from the parent,
         passing it the broadcast as two arguments, a SharedArrayBuffer and
-        an Int32.  This function may return before a broadcast is received
+        an Int32 or BigInt. This function may return before a broadcast is received
         (eg to return to an event loop to await a message) and no code should
         follow the call to this function.
       - **`report`** - a function that accepts a single "message" argument,
@@ -93,10 +93,11 @@ properties of the global scope prior to test execution.
       - **`leaving`** - a function that signals that the agent is done and
         may be terminated (if possible).
       - **`monotonicNow`** - a function that returns a value that conforms to [`DOMHighResTimeStamp`][] and is produced in such a way that its semantics conform to **[Monotonic Clock][]**.
-    - **`broadcast`** - a function that takes a SharedArrayBuffer and an Int32
-        and broadcasts the two values to all concurrent agents.  The function
-        blocks until all agents have retrieved the message.  Note, this assumes
-        that all agents that were started are still running.
+    - **`broadcast`** - a function that takes a SharedArrayBuffer and an 
+        Int32 or BigInt and broadcasts the two values to all concurrent 
+        agents. The function blocks until all agents have retrieved the 
+        message. Note, this assumes that all agents that were started are 
+        still running.
     - **`getReport`** - a function that reads an incoming string from any agent,
       and returns it if it exists, or returns `null` otherwise.
     - **`sleep`** - a function that takes a millisecond argument and

diff --git a/harness/atomicsHelper.js b/harness/atomicsHelper.js
@@ -28,6 +28,47 @@ description: >
     return r;
   };
 }
+
+/**
+ *
+ * Share a given Int32Array or BigInt64Array to all running agents. Ensure that the
+ * provided TypedArray is a "shared typed array".
+ *
+ * NOTE: Migrating all tests to this API is necessary to prevent tests from hanging
+ * indefinitely when a SAB is sent to a worker but the code in the worker attempts to
+ * create a non-sharable TypedArray (something that is not Int32Array or BigInt64Array).
+ * When that scenario occurs, an exception is thrown and the agent worker can no
+ * longer communicate with any other threads that control the SAB. If the main
+ * thread happens to be spinning in the $262.agent.waitUntil() while loop, it will never
+ * meet its termination condition and the test will hang indefinitely.
+ *
+ * Because we've defined $262.agent.broadcast(SAB) in
+ * https://github.com/tc39/test262/blob/master/INTERPRETING.md, there are host implementations
+ * that assume compatibility, which must be maintained.
+ *
+ *
+ * $262.agent.safeBroadcast(TA) should not be included in
+ * https://github.com/tc39/test262/blob/master/INTERPRETING.md
+ *
+ *
+ * @param {(Int32Array|BigInt64Array)} typedArray An Int32Array or BigInt64Array with a SharedArrayBuffer
+ */
+$262.agent.safeBroadcast = function(typedArray) {
+  let Constructor = Object.getPrototypeOf(typedArray).constructor;
+  let temp = new Constructor(
+    new SharedArrayBuffer(Constructor.BYTES_PER_ELEMENT)
+  );
+  try {
+    // This will never actually wait, but that's fine because we only
+    // want to ensure that this typedArray CAN be waited on and is shareable.
+    Atomics.wait(temp, 0, Constructor === Int32Array ? 1 : BigInt(1));
+  } catch (error) {
+    $ERROR(`${Constructor.name} cannot be used as a shared typed array. (${error})`);
+  }
+
+  $262.agent.broadcast(typedArray.buffer);
+};
+
 /**
  * With a given Int32Array or BigInt64Array, wait until the expected number of agents have
  * reported themselves by calling:
@@ -39,6 +80,7 @@ description: >
  * @param {number} expected The number of agents that are expected to report as active.
  */
 $262.agent.waitUntil = function(typedArray, index, expected) {
+
   var agents = 0;
   while ((agents = Atomics.load(typedArray, index)) !== expected) {
     /* nothing */
@@ -76,7 +118,7 @@ $262.agent.waitUntil = function(typedArray, index, expected) {
  *       $262.agent.leaving();
  *     });
  *   `);
- *   $262.agent.broadcast(i32a.buffer);
+ *   $262.agent.safeBroadcast(i32a.buffer);
  *
  *   // Wait until the agent was started and then try to yield control to increase
  *   // the likelihood the agent has called `Atomics.wait` and is now waiting.
@@ -106,7 +148,7 @@ $262.agent.waitUntil = function(typedArray, index, expected) {
  *       });
  *     `);
  *   }
- *   $262.agent.broadcast(i32a.buffer);
+ *   $262.agent.safeBroadcast(i32a.buffer);
  *
  *   // Wait until the agents were started and then try to yield control to increase
  *   // the likelihood the agents have called `Atomics.wait` and are now waiting.
@@ -151,7 +193,7 @@ $262.agent.waitUntil = function(typedArray, index, expected) {
  *       });
  *     `);
  *   }
- *   $262.agent.broadcast(i32a.buffer);
+ *   $262.agent.safeBroadcast(i32a.buffer);
  *
  *   // Wait until the agents were started and then try to yield control to increase
  *   // the likelihood the agents have called `Atomics.wait` and are now waiting.
@@ -204,7 +246,7 @@ $262.agent.timeouts = {
  *       $262.agent.leaving();
  *     });
  *   `);
- *   $262.agent.broadcast(i32a.buffer);
+ *   $262.agent.safeBroadcast(i32a.buffer);
  *
  *   // Wait until agent was started and then try to yield control.
  *   $262.agent.waitUntil(i32a, RUNNING, 1);

diff --git a/test/built-ins/Atomics/notify/bigint/notify-all-on-loc.js b/test/built-ins/Atomics/notify/bigint/notify-all-on-loc.js
@@ -57,7 +57,7 @@ const i64a = new BigInt64Array(
   new SharedArrayBuffer(BigInt64Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i64a, RUNNING, BigInt(NUMAGENT + 1));

diff --git a/test/built-ins/Atomics/notify/count-defaults-to-infinity-missing.js b/test/built-ins/Atomics/notify/count-defaults-to-infinity-missing.js
@@ -43,7 +43,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);
 
 // An agent may have been interrupted between reporting its initial report

diff --git a/test/built-ins/Atomics/notify/count-defaults-to-infinity-undefined.js b/test/built-ins/Atomics/notify/count-defaults-to-infinity-undefined.js
@@ -41,7 +41,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);
 
 // An agent may have been interrupted between reporting its initial report

diff --git a/test/built-ins/Atomics/notify/negative-count.js b/test/built-ins/Atomics/notify/negative-count.js
@@ -26,7 +26,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 4)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, 1);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/notify/notify-all-on-loc.js b/test/built-ins/Atomics/notify/notify-all-on-loc.js
@@ -57,7 +57,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT + 1);

diff --git a/test/built-ins/Atomics/notify/notify-all.js b/test/built-ins/Atomics/notify/notify-all.js
@@ -30,7 +30,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/notify-in-order-one-time.js b/test/built-ins/Atomics/notify/notify-in-order-one-time.js
@@ -42,7 +42,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/notify-in-order.js b/test/built-ins/Atomics/notify/notify-in-order.js
@@ -42,7 +42,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/notify-nan.js b/test/built-ins/Atomics/notify/notify-nan.js
@@ -26,7 +26,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 4)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, 1);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/notify/notify-one.js b/test/built-ins/Atomics/notify/notify-one.js
@@ -34,7 +34,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/notify-renotify-noop.js b/test/built-ins/Atomics/notify/notify-renotify-noop.js
@@ -26,7 +26,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 $262.agent.waitUntil(i32a, RUNNING, 1);
 

diff --git a/test/built-ins/Atomics/notify/notify-two.js b/test/built-ins/Atomics/notify/notify-two.js
@@ -34,7 +34,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/notify-with-no-agents-waiting.js b/test/built-ins/Atomics/notify/notify-with-no-agents-waiting.js
@@ -24,7 +24,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, 1);
 
 // There are ZERO agents waiting to notify...

diff --git a/test/built-ins/Atomics/notify/notify-with-no-matching-agents-waiting.js b/test/built-ins/Atomics/notify/notify-with-no-matching-agents-waiting.js
@@ -24,7 +24,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 2)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 $262.agent.waitUntil(i32a, RUNNING, 1);
 
 // There are ZERO matching agents waiting on index 1

diff --git a/test/built-ins/Atomics/notify/notify-zero.js b/test/built-ins/Atomics/notify/notify-zero.js
@@ -34,7 +34,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * BUFFER_SIZE)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait for agents to be running.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/notify/undefined-index-defaults-to-zero.js b/test/built-ins/Atomics/notify/undefined-index-defaults-to-zero.js
@@ -50,7 +50,7 @@ const i32a = new Int32Array(
   new SharedArrayBuffer(Int32Array.BYTES_PER_ELEMENT * 4)
 );
 
-$262.agent.broadcast(i32a.buffer);
+$262.agent.safeBroadcast(i32a);
 
 // Wait until both agents started.
 $262.agent.waitUntil(i32a, RUNNING, NUMAGENT);

diff --git a/test/built-ins/Atomics/wait/bigint/false-for-timeout-agent.js b/test/built-ins/Atomics/wait/bigint/false-for-timeout-agent.js
@@ -16,6 +16,10 @@ includes: [atomicsHelper.js]
 features: [Atomics, BigInt, SharedArrayBuffer, TypedArray]
 ---*/
 
+const i64a = new BigInt64Array(
+  new SharedArrayBuffer(BigInt64Array.BYTES_PER_ELEMENT * 4)
+);
+
 const RUNNING = 1;
 
 $262.agent.start(`
@@ -46,11 +50,7 @@ $262.agent.start(`
   });
 `);
 
-const i64a = new BigInt64Array(
-  new SharedArrayBuffer(BigInt64Array.BYTES_PER_ELEMENT * 4)
-);
-
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/nan-for-timeout.js b/test/built-ins/Atomics/wait/bigint/nan-for-timeout.js
@@ -33,7 +33,7 @@ const i64a = new BigInt64Array(
   new SharedArrayBuffer(BigInt64Array.BYTES_PER_ELEMENT * 4)
 );
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/negative-timeout-agent.js b/test/built-ins/Atomics/wait/bigint/negative-timeout-agent.js
@@ -25,7 +25,7 @@ const i64a = new BigInt64Array(
   new SharedArrayBuffer(BigInt64Array.BYTES_PER_ELEMENT * 4)
 );
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-no-operation.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-no-operation.js
@@ -38,7 +38,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-add.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-add.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-and.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-and.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-compareExchange.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-compareExchange.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-exchange.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-exchange.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-or.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-or.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-store.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-store.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.

diff --git a/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-sub.js b/test/built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-sub.js
@@ -31,7 +31,7 @@ $262.agent.start(`
   });
 `);
 
-$262.agent.broadcast(i64a.buffer);
+$262.agent.safeBroadcast(i64a);
 $262.agent.waitUntil(i64a, RUNNING, 1n);
 
 // Try to yield control to ensure the agent actually started to wait.