Question

当我调用NPN_GetValue时，我的插件代码崩溃了。基本上我创建了一个脚本化对象，它有一个'getDevice'方法，可以将设备数组返回给JavaScript。以下是代码段。

static bool mainNPObjectInvoke(NPObject *obj, NPIdentifier identifier, const NPVariant *args, uint32_t argCount, NPVariant *result)
{
    printf("create main object");
    MainNPObject *mainObject = (MainNPObject *)obj;

    if (identifier == methodIdentifiers[METHOD_ID_GET_DEVICES])
    {
        NPObject *windowObj = NULL;
        browser->getvalue(mainObject->npp, NPNVWindowNPObject, &windowObj);
        // it crashed here
    ....
    }
}

我使用以下方法创建了MainNPObject实例。

NPObject *createMainNPObject(NPP npp)
{
    MainNPObject *object = (MainNPObject *)browser->createobject(npp, &mainNPClass);
    object->npp = npp;

    theMainObject = object;

    return (NPObject *)object;
}

在我提供给浏览器的插件函数中调用createMainNPObject。

NPError NPP_GetValue(NPP instance, NPPVariable variable, void *value)
{
    PluginObject *obj = instance->pdata;

    switch (variable) {
        case NPPVpluginCoreAnimationLayer:
            if (!obj->rootLayer)
                setupLayerHierarchy(obj);

            *(CALayer **)value = obj->rootLayer;

            return NPERR_NO_ERROR;

        case NPPVpluginScriptableNPObject:

            if (!obj->mainObject)
            {
                obj->mainObject = createMainNPObject(instance);
            }
 ....
}

分配功能如下。

static NPObject *mainNPObjectAllocate(NPP npp, NPClass *class)
{
    initializeIdentifiers();

    MainNPObject *mainObject = malloc(sizeof(MainNPObject));
    mainObject->deviceManager = [[DeviceManager alloc] init];

    return (NPObject *)mainObject;
}

MainNPObject的定义：

typedef struct
{
    NPObject *npobject;
    NPP npp;
    DeviceManager *deviceManager;
} MainNPObject;

通过调试代码，我发现系统在调用browser-＆gt; getValue时引发了EXC_BAD_ACCESS，看起来npp指针无效。

0x00007fff83f82dab  <+0019>  je     0x7fff83f82db9 <_ZN6WebKit14NetscapePlugin7fromNPPEP4_NPP+33>
0x00007fff83f82dad  <+0021>  incl   0x8(%rax)

有人能帮助我吗？

谢谢！

Answer 1

嗯;看不出任何明显的东西尝试将另一个参数（一个int？）添加到您的结构中并在分配期间或之后立即设置它，然后检查它是否仍然是您在调用getvalue之前设置的值。看看你的结构是否以某种方式变得腐败。当我以非显而易见的方式投射NPObject时，这种情况发生在我身上。

Safari插件在NPN_GetValue上崩溃

1 个答案: