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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/278734">278734</a></dd>
<dt>Author</dt> <dd>keith_miller@apple.com</dd>
<dt>Date</dt> <dd>2021-06-10 14:54:36 -0700 (Thu, 10 Jun 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>Shouldn't drain the micro task queue when calling out to ObjC
https://bugs.webkit.org/show_bug.cgi?id=161942

Reviewed by Saam Barati.

It looks like the issue is that we aren't checking for the
presence of dropped locks when deciding to drain microtasks during
JSLock::unlock. This meant that when we drop all locks when
calling out to API clients we would drain our microtasks at that
point. An alternative would be to pass an extra parameter to the
unlock function that says not to drain microtasks. I chose not to
do that since it seemed a bit less robust.

This patch is very likely to break existing API users. So I'm adding
a linked on or after check to protect existing Apps.

Lastly, change our Poker Bros check to use applicationSDKVersion too
so others trying to add a linked on or after check don't use
the dyld function directly too.

* API/tests/testapi.cpp:
(TestAPI::promiseDrainDoesNotEatExceptions):
(testCAPIViaCpp):
* API/tests/testapi.mm:
(testMicrotaskWithFunction):
(testObjectiveCAPI):
* runtime/JSLock.cpp:
(JSC::JSLock::willReleaseLock):
* runtime/ObjectPrototype.cpp:
(JSC::isPokerBros):
* runtime/VM.cpp:
(JSC::VM::didExhaustMicrotaskQueue):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreAPIteststestapicpp">trunk/Source/JavaScriptCore/API/tests/testapi.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreAPIteststestapimm">trunk/Source/JavaScriptCore/API/tests/testapi.mm</a></li>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeJSLockcpp">trunk/Source/JavaScriptCore/runtime/JSLock.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeObjectPrototypecpp">trunk/Source/JavaScriptCore/runtime/ObjectPrototype.cpp</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeVMcpp">trunk/Source/JavaScriptCore/runtime/VM.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreAPIteststestapicpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/API/tests/testapi.cpp (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/API/tests/testapi.cpp        2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/API/tests/testapi.cpp   2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -38,6 +38,10 @@
</span><span class="cx"> #include <wtf/Vector.h>
</span><span class="cx"> #include <wtf/text/StringCommon.h>
</span><span class="cx"> 
</span><ins>+#if PLATFORM(COCOA)
+#include <wtf/cocoa/RuntimeApplicationChecksCocoa.h>
+#endif
+
</ins><span class="cx"> extern "C" void configureJSCForTesting();
</span><span class="cx"> extern "C" int testCAPIViaCpp(const char* filter);
</span><span class="cx"> extern "C" void JSSynchronousGarbageCollectForDebugging(JSContextRef);
</span><span class="lines">@@ -147,6 +151,7 @@
</span><span class="cx">     void promiseUnhandledRejection();
</span><span class="cx">     void promiseUnhandledRejectionFromUnhandledRejectionCallback();
</span><span class="cx">     void promiseEarlyHandledRejections();
</span><ins>+    void promiseDrainDoesNotEatExceptions();
</ins><span class="cx">     void topCallFrameAccess();
</span><span class="cx">     void markedJSValueArrayAndGC();
</span><span class="cx">     void classDefinitionWithJSSubclass();
</span><span class="lines">@@ -609,6 +614,27 @@
</span><span class="cx">     check(!callbackCalled, "unhandled rejection callback should not be called for asynchronous early-handled rejection");
</span><span class="cx"> }
</span><span class="cx"> 
</span><ins>+void TestAPI::promiseDrainDoesNotEatExceptions()
+{
+#if PLATFORM(COCOA)
+        bool useLegacyDrain = false;
+#if PLATFORM(MAC)
+        useLegacyDrain = applicationSDKVersion() < DYLD_MACOSX_VERSION_12_00;
+#elif PLATFORM(WATCH)
+            // Don't check, JSC isn't API on watch anyway.
+#elif PLATFORM(IOS_FAMILY)
+        useLegacyDrain = applicationSDKVersion() < DYLD_IOS_VERSION_15_0;
+#else
+#error "Unsupported Cocoa Platform"
+#endif
+        if (useLegacyDrain)
+            return;
+#endif
+    ScriptResult result = callFunction("(function() { Promise.resolve().then(() => { throw 2; }); throw 1; })");
+    check(!result, "function should throw an error");
+    check(JSValueIsNumber(context, result.error()) && JSValueToNumber(context, result.error(), nullptr) == 1, "exception payload should have been 1");
+}
+
</ins><span class="cx"> void TestAPI::topCallFrameAccess()
</span><span class="cx"> {
</span><span class="cx">     {
</span><span class="lines">@@ -760,6 +786,7 @@
</span><span class="cx">     RUN(promiseRejectTrue());
</span><span class="cx">     RUN(promiseUnhandledRejection());
</span><span class="cx">     RUN(promiseUnhandledRejectionFromUnhandledRejectionCallback());
</span><ins>+    RUN(promiseDrainDoesNotEatExceptions());
</ins><span class="cx">     RUN(promiseEarlyHandledRejections());
</span><span class="cx">     RUN(markedJSValueArrayAndGC());
</span><span class="cx">     RUN(classDefinitionWithJSSubclass());
</span><span class="lines">@@ -766,10 +793,8 @@
</span><span class="cx">     RUN(proxyReturnedWithJSSubclassing());
</span><span class="cx">     RUN(testJSObjectSetOnGlobalObjectSubclassDefinition());
</span><span class="cx"> 
</span><del>-    if (tasks.isEmpty()) {
-        dataLogLn("Filtered all tests: ERROR");
-        return 1;
-    }
</del><ins>+    if (tasks.isEmpty())
+        return 0;
</ins><span class="cx"> 
</span><span class="cx">     Lock lock;
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreAPIteststestapimm"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/API/tests/testapi.mm (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/API/tests/testapi.mm 2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/API/tests/testapi.mm    2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -2730,6 +2730,25 @@
</span><span class="cx">     }
</span><span class="cx"> }
</span><span class="cx"> 
</span><ins>+static void testMicrotaskWithFunction()
+{
+    @autoreleasepool {
+        JSContext *context = [[JSContext alloc] init];
+
+        JSValue *globalObject = context.globalObject;
+
+        auto block = ^() {
+            return 1+1;
+        };
+
+        [globalObject setValue:block forProperty:@"setTimeout"];
+        JSValue *arr = [context evaluateScript:@"var arr = []; (async () => { await 1; arr.push(3); })(); arr.push(1); setTimeout(); arr.push(2); arr;"];
+        checkResult(@"arr[0] should be 1", [arr[@0] toInt32] == 1);
+        checkResult(@"arr[1] should be 2", [arr[@1] toInt32] == 2);
+        checkResult(@"arr[2] should be 3", [arr[@2] toInt32] == 3);
+    }
+}
+
</ins><span class="cx"> @protocol ToString <JSExport>
</span><span class="cx"> - (NSString *)toString;
</span><span class="cx"> @end
</span><span class="lines">@@ -2848,6 +2867,8 @@
</span><span class="cx">     RUN(promiseCreateRejected());
</span><span class="cx">     RUN(parallelPromiseResolveTest());
</span><span class="cx"> 
</span><ins>+    RUN(testMicrotaskWithFunction());
+
</ins><span class="cx">     if (!filter)
</span><span class="cx">         testObjectiveCAPIMain();
</span><span class="cx"> }
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog    2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/ChangeLog       2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -1,3 +1,38 @@
</span><ins>+2021-06-10  Keith Miller  <keith_miller@apple.com>
+
+        Shouldn't drain the micro task queue when calling out to ObjC
+        https://bugs.webkit.org/show_bug.cgi?id=161942
+
+        Reviewed by Saam Barati.
+
+        It looks like the issue is that we aren't checking for the
+        presence of dropped locks when deciding to drain microtasks during
+        JSLock::unlock. This meant that when we drop all locks when
+        calling out to API clients we would drain our microtasks at that
+        point. An alternative would be to pass an extra parameter to the
+        unlock function that says not to drain microtasks. I chose not to
+        do that since it seemed a bit less robust.
+
+        This patch is very likely to break existing API users. So I'm adding
+        a linked on or after check to protect existing Apps.
+
+        Lastly, change our Poker Bros check to use applicationSDKVersion too
+        so others trying to add a linked on or after check don't use
+        the dyld function directly too.
+
+        * API/tests/testapi.cpp:
+        (TestAPI::promiseDrainDoesNotEatExceptions):
+        (testCAPIViaCpp):
+        * API/tests/testapi.mm:
+        (testMicrotaskWithFunction):
+        (testObjectiveCAPI):
+        * runtime/JSLock.cpp:
+        (JSC::JSLock::willReleaseLock):
+        * runtime/ObjectPrototype.cpp:
+        (JSC::isPokerBros):
+        * runtime/VM.cpp:
+        (JSC::VM::didExhaustMicrotaskQueue):
+
</ins><span class="cx"> 2021-06-10  Mark Lam  <mark.lam@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Another speculative build fix for Win32.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeJSLockcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/JSLock.cpp (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/JSLock.cpp   2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/runtime/JSLock.cpp      2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -1,5 +1,5 @@
</span><span class="cx"> /*
</span><del>- * Copyright (C) 2005-2018 Apple Inc. All rights reserved.
</del><ins>+ * Copyright (C) 2005-2021 Apple Inc. All rights reserved.
</ins><span class="cx">  *
</span><span class="cx">  * This library is free software; you can redistribute it and/or
</span><span class="cx">  * modify it under the terms of the GNU Library General Public
</span><span class="lines">@@ -33,6 +33,10 @@
</span><span class="cx"> #include <wtf/ios/WebCoreThread.h>
</span><span class="cx"> #endif
</span><span class="cx"> 
</span><ins>+#if PLATFORM(COCOA)
+#include <wtf/cocoa/RuntimeApplicationChecksCocoa.h>
+#endif
+
</ins><span class="cx"> namespace JSC {
</span><span class="cx"> 
</span><span class="cx"> Lock GlobalJSLock::s_sharedInstanceMutex;
</span><span class="lines">@@ -197,8 +201,25 @@
</span><span class="cx"> {   
</span><span class="cx">     RefPtr<VM> vm = m_vm;
</span><span class="cx">     if (vm) {
</span><del>-        vm->drainMicrotasks();
</del><ins>+        static bool useLegacyDrain = false;
+#if PLATFORM(COCOA)
+        static std::once_flag once;
+        std::call_once(once, [] {
+#if PLATFORM(MAC)
+            useLegacyDrain = applicationSDKVersion() < DYLD_MACOSX_VERSION_12_00;
+#elif PLATFORM(WATCH)
+            // Don't check, JSC isn't API on watch anyway.
+#elif PLATFORM(IOS_FAMILY)
+            useLegacyDrain = applicationSDKVersion() < DYLD_IOS_VERSION_15_0;
+#else
+#error "Unsupported Cocoa Platform"
+#endif
+        });
+#endif
</ins><span class="cx"> 
</span><ins>+        if (!m_lockDropDepth || useLegacyDrain)
+            vm->drainMicrotasks();
+
</ins><span class="cx">         if (!vm->topCallFrame)
</span><span class="cx">             vm->clearLastException();
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeObjectPrototypecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/ObjectPrototype.cpp (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/ObjectPrototype.cpp  2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/runtime/ObjectPrototype.cpp     2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -29,7 +29,7 @@
</span><span class="cx"> #include "PropertySlot.h"
</span><span class="cx"> 
</span><span class="cx"> #if PLATFORM(IOS)
</span><del>-#include <wtf/spi/darwin/dyldSPI.h>
</del><ins>+#include <wtf/cocoa/RuntimeApplicationChecksCocoa.h>
</ins><span class="cx"> #endif
</span><span class="cx"> 
</span><span class="cx"> namespace JSC {
</span><span class="lines">@@ -322,7 +322,7 @@
</span><span class="cx">     auto bundleID = CFBundleGetIdentifier(CFBundleGetMainBundle());
</span><span class="cx">     return bundleID
</span><span class="cx">         && CFEqual(bundleID, CFSTR("com.kpgame.PokerBros"))
</span><del>-        && dyld_get_program_sdk_version() < DYLD_IOS_VERSION_14_0;
</del><ins>+        && applicationSDKVersion() < DYLD_IOS_VERSION_14_0;
</ins><span class="cx"> }
</span><span class="cx"> #endif
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeVMcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/VM.cpp (278733 => 278734)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/VM.cpp       2021-06-10 21:19:59 UTC (rev 278733)
+++ trunk/Source/JavaScriptCore/runtime/VM.cpp  2021-06-10 21:54:36 UTC (rev 278734)
</span><span class="lines">@@ -1368,13 +1368,15 @@
</span><span class="cx"> 
</span><span class="cx"> void VM::didExhaustMicrotaskQueue()
</span><span class="cx"> {
</span><del>-    auto unhandledRejections = WTFMove(m_aboutToBeNotifiedRejectedPromises);
-    for (auto& promise : unhandledRejections) {
-        if (promise->isHandled(*this))
-            continue;
</del><ins>+    do {
+        auto unhandledRejections = WTFMove(m_aboutToBeNotifiedRejectedPromises);
+        for (auto& promise : unhandledRejections) {
+            if (promise->isHandled(*this))
+                continue;
</ins><span class="cx"> 
</span><del>-        callPromiseRejectionCallback(promise);
-    }
</del><ins>+            callPromiseRejectionCallback(promise);
+        }
+    } while (!m_aboutToBeNotifiedRejectedPromises.isEmpty());
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> void VM::promiseRejected(JSPromise* promise)
</span></span></pre>
</div>
</div>

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