[Metal] GPUStartTime/GPUEndTime availability

It sounds like you may be doing something unusual with the SDK version or something. The normal way to handle this is to target the current SDK version and then just change the deployment version to whatever old version you want to support. In your code, you will have to avoid any references to newer symbols at runtime.

Here is documentation from Apple describing how to do this.

It can be tricky because new Xcode versions often have templates and sample code that will only work on the latest version and is not backwards compatible at all. Many of those availability macros are designed for building code that could potentially run on different OS versions but isn't actually helpful for writing your own backwards-compatible code.

You compile using the SDK version that you have. If your development machine is running 10.15, then you should be using the latest version of Xcode that runs on 10.15. According to this site, you should be running Xcode 12.4.

Then, you set the deployment target to 10.13. Your app will now run on anything from 10.13-12.1. It is your responsibility to make sure that any symbols you reference actually exist on 10.13. At this point, there is little risk of anything breaking on any OS versions in the foreseeable future.

Don't use those functions if you need 10.13 support.

However, there is very little value to maintaining 10.13 support in the first place. The only people still using 10.13 are people who have 10 year-old computers that 1) can no longer be updated and 2) are still running.

If you aren't directly calling those functions, then you may be using some 3rd party framework that does.

_matrix wrote:

In my opinion the problem lies in the headers.

The headers are fine. Make sure you aren't doing anything unusual. Download one of the Metal sample apps from Apple and build it. You don't have to do anything fancy. Just accept all defaults.

Then, if you want the sample app to run on 10.13, just change the deployment and test it on 10.13. I don't know if the compiler is smart enough to check backwards compatibility with the deployment target. This might be something that Swift can do, but not Objective-C.

With OpenCL it is possible to use external headers, but with Metal the only thing Apple releases is metal-cpp.

https://developer.apple.com/metal/cpp/

No. That's something different. Your problem here is with the Metal framework itself. I'm still not sure what you are doing wrong. But those GPUStartTime/GPUEndTime properties are just regular Objective-C/Swift properties. While they are part of the Metal framework, they aren't themselves "Metal".

What you linked to with metal-cpp is the Metal shader language. That is the language that your MTLCommandBuffer is going to ultimately execute on the GPU.

I should do some tests to understand if it is actually possible to use these headers instead of those present by default in the operating system.

You are going in the wrong direction here. You don't want to try additional funky things that aren't going to work. Just use the defaults. They are guaranteed to work. The only reason you are having trouble now is because you are trying to do something funky.

Beyond that it would be useful to understand if there are license restrictions, so if for example it is possible to use all this in an open-source software with an MIT license.

There are no license restrictions on your own code. Anything you release that uses Metal would, or course, require the appropriate Metal support. An MIT license would be fine. However, the "free software" folks might not like it if you have dependencies on non-"free" APIs like Metal. But that is strictly a social thing. They will say mean things about you on Twitter and some IRC protocol from the 1980s. There are no legal restrictions.

Are you are trying to build on 10.13? And you just want to run it and hope it works on 12.1?

I guess you can call "NSSelectorFromString" to create a selector. Then call "respondsToSelector" and if it returns true, issue "performSelector". Good luck!