ASSERTION FAILURE: qantas.com.au changing selected item in <select> via JS

[Mark Rowe (bdash)]

Steps to reproduce:
1. Load <http://www.qantas.com.au/regions/dyn/home/qualifier-region-au>.
2. Select 'April 2007' from the "Depart" dropdown.
3. From the "Return" day dropdown select "Tuesday 10".

Expected results:
Page updates to match new selection.

Actual results:
Beachball, then crash.

0   com.apple.WebCore              	0x010aa4d4 WebCore::HTMLSelectElement::setSelectedIndex(int, bool, bool) + 326 (HTMLSelectElement.cpp:188)
1   com.apple.WebCore              	0x013c278d WebCore::JSHTMLSelectElement::putValueProperty(KJS::ExecState*, int, KJS::JSValue*, int) + 153 (JSHTMLSelectElement.cpp:224)
2   com.apple.WebCore              	0x015bf15a bool KJS::lookupPut<WebCore::JSHTMLSelectElement>(KJS::ExecState*, KJS::Identifier const&, KJS::JSValue*, int, KJS::HashTable const*, WebCore::JSHTMLSelectElement*) + 162 (lookup.h:254)

Will attach the full backtrace.

[Mark Rowe (bdash)]

Created attachment 13448 [details]
Crash log

[Alexey Proskuryakov]

I cannot reproduce this with r19943 on a PowerPC Mac.

[Jeff McGlynn]

I cannot reproduce this in r19940, r18726, r17722, r16233, or Safari 2.0.4 (419.3).  I'm using a 10.4.8 on a PPC architecture.

[Mark Rowe (bdash)]

I cannot reproduce this either.  This may be because the select lists have changed contents due to dates, or it may have been timing related.  I was seeing this initially with r19940 and retesting there doesn't reproduce the problem.  I'll leave this open and retest this in a few days to see if i can find other conditions to trigger this.

[Mark Rowe (bdash)]

As the crash log notes this is an assertion failure rather than a crash, so there is no way this will be triggered in a nightly build.  I can reproduce this easily again today while I was unable during the weekend.

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0xbbadbeef
0x010aa2c4 in WebCore::HTMLSelectElement::setSelectedIndex (this=0x1b957c60, optionIndex=0, deselect=true, fireOnChange=false) at /Users/mrowe/Documents/Work/Apple/OpenSource/WebCore/html/HTMLSelectElement.cpp:188
188         ASSERT(m_lastOnChangeIndex == -1 || m_lastOnChangeIndex == optionIndex);
(gdb) print m_lastOnChangeIndex
$1 = 2
(gdb) print optionIndex
$2 = 0

[Mark Rowe (bdash)]

Further investigation shows that this is happening when the selectedIndex on the <select> element is set inside an onchange event handler of the element.

[Mark Rowe (bdash)]

Created attachment 13475 [details]
Reduction

Truncating the select element's options and changing selectedIndex from within the onchange event handler will trigger the assertion failure.

[Mark Rowe (bdash)]

Created attachment 13485 [details]
Patch

[Mark Rowe (bdash)]

Landed in r20001.