1 files changed, 104 insertions, 0 deletions
diff --git a/modules/libpref/test/unit_ipc/test_large_pref.js b/modules/libpref/test/unit_ipc/test_large_pref.js
new file mode 100644
index 0000000000..79c1330c36
--- /dev/null
+++ b/modules/libpref/test/unit_ipc/test_large_pref.js
@@ -0,0 +1,104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Large preferences should not be set in the child process.
+// Non-string preferences are not tested here, because their behavior
+// should not be affected by this filtering.
+//
+
+function isParentProcess() {
+  return Services.appinfo.processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT;
+}
+
+function makeBuffer(length) {
+  let string = "x";
+  while (string.length < length) {
+    string = string + string;
+  }
+  if (string.length > length) {
+    string = string.substring(length - string.length);
+  }
+  return string;
+}
+
+// from prefapi.h
+const MAX_ADVISABLE_PREF_LENGTH = 4 * 1024;
+
+const largeString = makeBuffer(MAX_ADVISABLE_PREF_LENGTH + 1);
+const smallString = makeBuffer(4);
+
+const testValues = [
+  { name: "None", value: undefined },
+  { name: "Small", value: smallString },
+  { name: "Large", value: largeString },
+];
+
+function prefName(def, user) {
+  return "Test.IPC.default" + def.name + "User" + user.name;
+}
+
+function expectedPrefValue(def, user) {
+  if (user.value) {
+    return user.value;
+  }
+  return def.value;
+}
+
+function run_test() {
+  const pb = Services.prefs;
+  let defaultBranch = pb.getDefaultBranch("");
+
+  let isParent = isParentProcess();
+  if (isParent) {
+    // Preferences with large values will still appear in the shared memory
+    // snapshot that we share with all processes. They should not, however, be
+    // sent with the list of changes on top of the snapshot.
+    //
+    // So, make sure we've generated the initial snapshot before we set the
+    // preference values by launching a child process with an empty test.
+    sendCommand("");
+
+    // Set all combinations of none, small and large, for default and user prefs.
+    for (let def of testValues) {
+      for (let user of testValues) {
+        let currPref = prefName(def, user);
+        if (def.value) {
+          defaultBranch.setCharPref(currPref, def.value);
+        }
+        if (user.value) {
+          pb.setCharPref(currPref, user.value);
+        }
+      }
+    }
+
+    run_test_in_child("test_large_pref.js");
+  }
+
+  // Check that each preference is set or not set, as appropriate.
+  for (let def of testValues) {
+    for (let user of testValues) {
+      if (!def.value && !user.value) {
+        continue;
+      }
+      let pref_name = prefName(def, user);
+      if (isParent || (def.name != "Large" && user.name != "Large")) {
+        Assert.equal(pb.getCharPref(pref_name), expectedPrefValue(def, user));
+      } else {
+        // This is the child, and either the default or user value is
+        // large, so the preference should not be set.
+        let prefExists;
+        try {
+          let val = pb.getCharPref(pref_name);
+          prefExists = val.length > 128;
+        } catch (e) {
+          prefExists = false;
+        }
+        ok(
+          !prefExists,
+          "Pref " + pref_name + " should not be set in the child"
+        );
+      }
+    }
+  }
+}