зеркало из https://github.com/mozilla/gecko-dev.git
85 строки
3.6 KiB
HTML
85 строки
3.6 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<script>
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// Morph a slim wrapper into an XPCWN by generating a cross-compartment wrapper
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// for it (we Morph in WrapperFactory::PrepareForWrapping).
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function makeNonSlim(elem) {
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window.parent.someCCW = elem;
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delete window.parent.someCCW;
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}
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function doTest() {
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// Get a slim wrapper for |form|. This lives in scope 1.
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var form = document.getElementById('myform');
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// The gist here is that we want to create an input element that isn't part
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// of a form, so that its PreCreate hook will cause it to be parented to the
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// document. However, there are several considerations that make this more
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// complicted.
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//
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// First, the crashtest becomes non-deterministics if we morph |form| before
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// getting to scope 3 (as explained below). This means that we can't trigger
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// the PreCreate hook for |input|, because that will call WrapNativeParent
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// (Well... No, it won't: there is no WrapNativeParent, but there are also no
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// more pre-create hooks, slimwrappers, parenting to the form, or any of the
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// stuff this test is trying to test.)
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// on the form, which will end up making a cross-compartment wrapper, which
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// will morph form. But this puts us in a pickle, because appendChild returns
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// the apppended child, which will trigger the PreCreate hook in
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// NativeInterface2JSObject. So we do this little hack where we append a buch
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// of dummy <div> children to the form, and use replaceChild (which returns
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// the replacer, not the replacee) to stick the input elements as children of
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// the form.
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//
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// Second, the crashtest can also be non-deterministics if the final call to
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// MoveWrappers iterates over the hashtable in such a way that it fixes up
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// the Document before it fixes up the Input. If so, the Input will become
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// orphaned, and we'll detect it and fix things up at the top of MoveWrapper.
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// Since we can't control the hashtable ordering here, we just make 100 input
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// elements, to make it a near-certainty (statistically) that we'll encounter
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// one of them during iteration before encountering the Document.
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//
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// With all this, this testcase deterministically crashes on my machine. Whew!
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// Create an input element. This isn't part of a form right now, so it gets
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// parented to the document.
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var inputs = [];
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var placeHolders = [];
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for (var i = 0; i < 100; ++i) {
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var dummyDiv = form.appendChild(document.createElement('div'));
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var input = document.createElement('input');
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makeNonSlim(input);
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inputs.push(input);
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placeHolders.push(dummyDiv);
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}
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// Blow away the document, forcing a transplan of all the XPCWNs in scope. This
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// will transplant |input|, but |form| stays in the old scope (since it's slim).
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document.open();
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document.close();
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// Now we're in scope 2. Associate |input| with |form| so that the next call to
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// PreCreate will parent |input| to |form| rather than the document. But make
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// sure to do it with replaceChild, rather than appendChild, so that we don't
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// end up triggering the PreCreate hook for |form| in scope 2, which would make
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// make it non-slim. If we didn't, the ensuing call to MoveWrappers might find
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// |form| before |input| while iterating over the hashtable. If so, |form|
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// would be rescued as an orphan and everything would be fixed before getting to // |input|.
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for (var i = 0; i < inputs.length; ++i)
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form.replaceChild(inputs[i], placeHolders[i]);
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// Blow away the document a second time. This should cause the crash in
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// unpatched builds.
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document.open();
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document.close();
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}
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</script>
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</head>
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<body>
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<form id="myform"></form>
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</body>
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</html>
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