Getting stuck with translating a C Macro creates a Struct

Question

Getting stuck with translating a C Macro creates a Struct into a custom def declaration that will create a instance of MQTTClient connectOptions generated class in the KLib This is part of a Kotlin Native program which uses the Eclipse Paho MQTT Client library

msink · Answer

Something like this maybe ``` static inline void MQTTClient connectOptions initialize struct MQTTClient connectOptions value value = MQTTClient connectOptions initializer ```

olonho · Answer

yeah Mike got the general pattern right if you see no way to do smth in K N just add C function into def file and do it there However we will investigate how to do structure initialization right

napperley · Answer

Especially tricky when it is not clear which order the properties in a struct are being initialised when it comes to default values

napperley · Answer

Is there a way to get more informative error messages from the cinterop tool End up with the following error after adding in the workaround in the def file ```Exception in thread main java lang Error tmp tmp18083280284659516124 c 3 14 error expected expression```

msink · Answer

Well yes this was not valid C But this should work ``` static inline void MQTTClient connectOptions initialize MQTTClient connectOptions value MQTTClient connectOptions initializer = MQTTClient connectOptions initializer value = initializer ```

svyatoslav.scherbina · Answer

< napperley> you may be interested in taking a look at this Kotlin Native application using MQTT For example ` def` file

svyatoslav.scherbina · Answer

By the way this project is written by < madhead>

napperley · Answer

This error is outputted by konanc when trying to get a pointer from a CVariable MQTTClientVar ``` error unresolved reference None of the following candidates is applicable because of receiver type mismatch public final val lt T CVariable gt CValues lt MQTTClientVar = CPointerVarOf lt MQTTClient = CPointer lt out CPointed gt gt gt ptr CPointer lt MQTTClientVar = CPointerVarOf lt MQTTClient = CPointer lt out CPointed gt gt gt defined in kotlinx cinterop MemScope createMqttClient client ptr brokerUrl clientId MQTTCLIENT PERSISTENCE NONE null ```

napperley · Answer

Here is the Klib definition ``` fun MQTTClient create handle CValuesRef lt MQTTClientVar = CPointerVarOf lt MQTTClient = CPointer lt out CPointed gt gt gt serverURI String clientId String persistence type Int persistence context CValuesRef lt gt Int ```

madhead · Answer

How do you define `client`

napperley · Answer

Like this ```memScoped val client = alloc lt MQTTClientVar gt ```

olonho · Answer

could you provide self containing non compiling source please

napperley · Answer

See the MQTT Sample snippet <https kotlinlang slack com files U5R5FGVH7 FBEGLHWF6 mqtt sample kt>