Diego Fernandez wrote:
> I know that <> is used in primitives, but in calls to external
> libraries there is a performance reason for this kind of notation?
> Have this kind of methods different bycodes (like in primitives) or
> it's only a shorthand for the longer expression?

It's both a shorthand and a "statically compiled version" of the longer 
expression. Here is something that is essentially equivalent:

1. Using <> syntax:

Foo>>callSomething
      <cdecl: void 'callSomething' () module: 'Foo'>
      Transcript cr; show: 'Failed to call function'.

2. Using the (mostly) equivalent explicit version:

Object subclass: #Foo
     instanceVariableNames: ''
     classVariableNames: 'CallSomething'
     poolDictionaries: ''
     category: 'Croquet-Harness'

Foo class>>initialize
     "Construct the FFI call for callSomething"
     CallSomething := ExternalLibraryFunction
         name:'callSomething'
         module: 'Foo'
         callType: ExternalFunction callTypeCDecl
         returnType: ExternalType void
         argumentTypes: #()

Foo>>callSomething
     ^[CallSomething invoke] on: PrimitiveFailed do:[
         Transcript cr; show: 'Failed to call function'.
      ].

The reason this is only "mostly" equivalent is that there isn't a 
PrimitiveFailed exception (but there should be ;-)

Cheers,
   - Andreas