Each call to NPN_UserAgent leaks an NSString object on the Mac. How I discovered the bug: I was calling NPN_UserAgent in NPP_HandleEvent, and I noticed a slow leak. I opened ObjectAlloc.tracetemplate and did a trace of Safari, and it showed a leak of an object of roughly 170 bytes happening at nearly 60 times per second, and the stack trace showed the leak coming from NPN_UserAgent.
I cannot reproduce this with ToT. Could you please post a full stack trace? Also, are you seeing this in Safari on Mac OS X 10.5? Could you please try to reproduce this with a nightly build from <http://nightly.webkit.org>?
I reproduced it in Monday's ToT WebKit build. Stack trace of one of the leaked objects (from ObjectAlloc): 21 Safari 0x2c92 20 AppKit NSApplicationMain 19 AppKit -[NSApplication run] 18 Safari 0xc303 17 AppKit -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] 16 AppKit _DPSNextEvent 15 HIToolbox BlockUntilNextEventMatchingListInMode 14 HIToolbox ReceiveNextEventCommon 13 HIToolbox RunCurrentEventLoopInMode 12 CoreFoundation CFRunLoopRunInMode 11 CoreFoundation CFRunLoopRunSpecific 10 WebKit WebNetscapePluginEventHandlerCarbon::sendNullEvent() /Users/dwebb/Keyhole-local/WebKit/WebKit/mac/Plugins/WebNetscapePluginEventHandlerCarbon.mm:124 9 WebKit WebNetscapePluginEventHandlerCarbon::sendEvent(EventRecord*) /Users/dwebb/Keyhole-local/WebKit/WebKit/mac/Plugins/WebNetscapePluginEventHandlerCarbon.mm:420 8 WebKit -[WebNetscapePluginDocumentView sendEvent:isDrawRect:] /Users/dwebb/Keyhole-local/WebKit/WebKit/mac/Plugins/WebNetscapePluginView.mm:672 7 libnpgeplugin.dylib Private_HandleEvent(_NPP*, void*) 6 libnpgeplugin.dylib nsPluginInstance::HandleEvent(void*) scons-out/opt/obj/apps/earth/plugin/idlglue/staticglue/moz/plugin.cc:164 5 libnpgeplugin.dylib GetNPSupportedModels(_NPP*, bool*, bool*, bool*) 4 WebKit NPN_UserAgent /Users/dwebb/Keyhole-local/WebKit/WebKit/mac/Plugins/npapi.mm:120 3 Foundation -[NSCFString UTF8String] 2 Foundation bytesInEncoding 1 CoreFoundation __CFDataInit 0 CoreFoundation _CFRuntimeCreateInstance If you want to reproduce it using the Google Earth plugin, download the installer from here, install it, and reload the page (might require Safari restart): <http://code.google.com/apis/earth/>
That appears to show the char* buffer returned by NPN_UserAgent is being leaked. I would assume that the caller of NPN_UserAgent is responsible for freeing that memory. Is that not the case?
Hmm, I assumed that the string was owned by npapi, since the docs didn't mention anything about handing off ownership of the C string. <http://developer.mozilla.org/en/NPN_UserAgent> I googled around a bit and found some example code that doesn't free the string: <https://developer.mozilla.org/en/Gecko_Plugin_API_Reference/Initialization_and_Destruction#Initialize_and_Shutdown_Example>
If I'm looking at the right place, Mozilla does return a pointer to static buffer: <http://mxr.mozilla.org/mozilla-central/source/modules/plugin/base/src/nsPluginHost.cpp#2612> indeed.