Bug 1582741 - Create a test for balanced native allocation; r=canaltinova

This file adds coverage for the balanced native allocations feature from the
previous commit. It asserts that a de-allocation will have a matching allocation.

Differential Revision: https://phabricator.services.mozilla.com/D51936

--HG--
extra : moz-landing-system : lando

tools/profiler/tests/xpcshell/test_feature_nativeallocations.js

@@ -31,19 +31,14 @@ add_task(async () => {
     );
     doWork();
 
-    info(
-      "Go ahead and wait for a periodic sample as well, in order to make sure that " +
-        "the native allocations play nicely with the rest of the profiler machinery."
-    );
-    await Services.profiler.waitOnePeriodicSampling();
-
     info("Get the profile data and analyze it.");
     const profile = await stopAndGetProfile();
 
-    const allocationPayloads = getPayloadsOfType(
-      profile.threads[0],
-      "Native allocation"
-    );
+    const {
+      allocationPayloads,
+      unmatchedAllocations,
+      logAllocationsAndDeallocations,
+    } = getAllocationInformation(profile);
 
     Assert.greater(
       allocationPayloads.length,
@@ -51,6 +46,23 @@ add_task(async () => {
       "Native allocation payloads were recorded for the parent process' main thread when " +
         "the Native Allocation feature was turned on."
     );
+
+    if (unmatchedAllocations.length !== 0) {
+      info(
+        "There were unmatched allocations. Log all of the allocations and " +
+          "deallocations in order to aid debugging."
+      );
+      logAllocationsAndDeallocations();
+      ok(
+        false,
+        "Found a deallocation that did not have a matching allocation site. " +
+          "This could happen if balanced allocations is broken, or if the the " +
+          "buffer size of this test was too small, and some markers ended up " +
+          "rolling off."
+      );
+    }
+
+    ok(true, "All deallocation sites had matching allocations.");
   }
 
   info("Restart the profiler, to ensure that we get no more allocations.");
@@ -81,3 +93,64 @@ function doWork() {
     this.n += Math.random();
   }
 }
+
+/**
+ * Extract the allocation payloads, and find the unmatched allocations.
+ */
+function getAllocationInformation(profile) {
+  // Get all of the allocation payloads.
+  const allocationPayloads = getPayloadsOfType(
+    profile.threads[0],
+    "Native allocation"
+  );
+
+  // Decide what is an allocation and deallocation.
+  const allocations = allocationPayloads.filter(
+    payload => ensureIsNumber(payload.size) >= 0
+  );
+  const deallocations = allocationPayloads.filter(
+    payload => ensureIsNumber(payload.size) < 0
+  );
+
+  // Now determine the unmatched allocations by building a set
+  const allocationSites = new Set(
+    allocations.map(({ memoryAddress }) => memoryAddress)
+  );
+
+  const unmatchedAllocations = deallocations.filter(
+    ({ memoryAddress }) => !allocationSites.has(memoryAddress)
+  );
+
+  // Provide a helper to log out the allocations and deallocations on failure.
+  function logAllocationsAndDeallocations() {
+    for (const { memoryAddress } of allocations) {
+      console.log("Allocations", formatHex(memoryAddress));
+      allocationSites.add(memoryAddress);
+    }
+
+    for (const { memoryAddress } of deallocations) {
+      console.log("Deallocations", formatHex(memoryAddress));
+    }
+
+    for (const { memoryAddress } of unmatchedAllocations) {
+      console.log("Deallocation with no allocation", formatHex(memoryAddress));
+    }
+  }
+
+  return {
+    allocationPayloads,
+    unmatchedAllocations,
+    logAllocationsAndDeallocations,
+  };
+}
+
+function ensureIsNumber(value) {
+  if (typeof value !== "number") {
+    throw new Error(`Expected a number: ${value}`);
+  }
+  return value;
+}
+
+function formatHex(number) {
+  return `0x${number.toString(16)}`;
+}