Safe Calls

[codeservice]

[codeservice]

I can't use catch(Dynamic e) in CFFI integration. Dynamic object not accessible here. Only way is to use callback function.

[hughsando]

Yes, catching is problematic. What do you think of the idea of passing in a "value *" instead of the callback, then check for non-null returned exception in the c++ code? The callback is probably going to be written in c++, not haxe, so this might be more convenient. If it was haxe, then you could write the catching as part of the function call itself. Adding functions to the api is a bit tricky, since neko must be considered and I have not yet added a way of checking the version of the host (eg, new dll, old host) but we can deal with that later.

[codeservice]

I am using callback from haxe, not cpp. Passing callback haxe function as parameter to CFFI on initializtion. Because it’s on haxe side, callback code can be easily modified.

I’ll check how it can be done from cpp.

[hughsando]

Dynamic basically has a single member, mPtr, which is a hx::Object *, which is actually a 'value'. So if you catch a Dynamic from the api implementation you can just typecast the e.mPtr to value, which should make things easier.

To do the catching in haxe, you could make a "safecaller" instead of a callback. like:

   static function callback(e:Dynamic)  { ... }

   static function callSafe(func:Dynamic, arg1:Dynamic)
   {
      try {
         func(arg1);
      }
     catch(e:Dynamic)
     {
         callback(e);
     }
   }

   // Then, when you set the callback, do:
   library.setSafeCall(callSafe);
   // instead of
   // library.setCallback(callback);

   // from c++:
  val_call2(callSafe, func, arg1)
  // instead of
  // val_call_safe1(func,arg1,callback)

[codeservice]

Using haxe safecaller I can't catch other cpp exceptions, only haxe Dynamic type. static function callSafe(func:Dynamic, arg1:Dynamic) { try { func(arg1); } catch(e:Dynamic) //limited to haxe exception type { callback(e); } }

In cpp I can use catch(...) for any type, making call really safe. I'll try this option "passing in a "value *" instead of the callback"

[codeservice]

I think I am wrong, its possible if I wrap val_call in try / catch: try { val_call2(callSafe, func, arg1) } catch(...){ //... }

For me performance important, need to check haxe safecaller version ...

P.S. Only incontinence now I have two spots for handling exception, one in haxe and one in cpp "passing in a "value *" instead of the callback" looks more convenient.

P.P.S. and safecaller slower: val_call2 -> callsafe -> func chain of calls instead of more direct val_call_safe1 -> func

[hughsando]

This should work if you static-link the nme library. I'm not sure if the type-information is consistent between dlls and the main program - but I guess if the catch does not depend on the type, it might just work.

On Tue, Aug 20, 2019 at 10:00 PM codeservice [email protected] wrote:

I think I am wrong, its possible if I wrap val_call in try / catch: try { val_call2(callSafe, func, arg1) } catch(...){ //... }

For me performance important, need to check haxe safecaller version ...

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[codeservice]

Its for different library, not NME. In some cases I can't statically link other libraries. For example, I didn't find way statically link LuaJIT, don't think this even possible. Probably easiest way for me to keep using custom hxcpp modification from my local hxcpp version.