ContactListener events lifetime

[Froyok]

Hi,

I likely have a very simple question, but being not super familiar with C/C++ in general I prefer to ask to be sure. I hope you won't mind.

First to give some context: I'm using the C wrapper of Jolt C# version to support Jolt Physics in my project. My project is built in Love which is a framework that run Lua scripts. With the library FFI I'm able to use external C libraries, so that's how I'm able to get Jolt working.

I got basic objects and collisions working and I started to look at sensors (for trigger volume mainly). Because Love use LuaJit to provide good performance, there is a limitation around callbacks. Callbacks cannot be triggered from another thread, which is what Jolt does by default. My solution to this has been to write another little C shared library to wrap the callback function (with the idea of using a mutex lock and storing the event results into an array I would access later).

My question is the following: because the ContactListener function gives pointer to objects, what is the lifetime of those objects ? Can I expect them to still be valid even after the Update function of the physics system has run (aka until the next one) ? Or should I do an explicit copy of the data ? Thinking about the ContactSettings for example.

My idea what to store the add/remove event in arrays that I would consult after the Update function ran.

[jrouwe]

• OnContactValidate - you need to immediately provide a response, so this one cannot be queued
• OnContactAdded/Persisted - as long as you don't destroy the bodies yourself, the bodies should remain valid. ContactManifold is allocated on the stack, so need to be copied. ContactSettings needs to be filled in immediately by the callback, so there's no point in storing this.
• OnContactRemoved - this one only gets IDs, these can point to already deleted bodies. When you try to get a Body pointer from an ID the system will let you know they no longer exist, so you can queue these too.

[Froyok]

That clarified everything, thank you very much ! :)