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dev:crosscompiler:class_initialization

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dev:crosscompiler:class_initialization [2014/11/03 13:31] – external edit 127.0.0.1dev:crosscompiler:class_initialization [2021/05/10 19:52] (current) – ursgraf
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 </code> </code>
 ==== When will a class be initialized? ==== ==== When will a class be initialized? ====
-On the host we have a situation like this. The class constructor of a top-level class will be called first. Then follows the method //main//. The class constructor of an imported class will be called when:+On the host we have a situation as follows. The class constructor of a top-level class will be called first. Then follows the method //main//. The class constructor of an imported class will be called when:
   * accessing a static field of an imported class   * accessing a static field of an imported class
   * calling a static method of an imported class   * calling a static method of an imported class
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   }   }
 </code> </code>
-Class A starts initializing, //a1 = b1 + 1// causes //clinit// of class B to be executed after which //clinit// of class A finishes. //a1// will be assigned the correct value of 101, but //b2// will be assigned 1 instaed of 201.+Class A starts initializing, //a1 = b1 + 1// causes //clinit// of class B to be executed after which //clinit// of class A finishes. //a1// will be assigned the correct value of 101, but //b2// will be assigned 1 instead of 201.
 This error goes undetected. A user has to make sure that the initialization is done in a correct way.  This error goes undetected. A user has to make sure that the initialization is done in a correct way. 
  
 ==== Our Solution ==== ==== Our Solution ====
-Beim Linken sollen alle Top-Level Klassen als Parameter angegeben werden können. Diese Liste wird von links nach rechts geparst und die Imports in der richtigen Reihenfolge aufgelöst. Wenn sich Probleme mit zyklischen Imports ergeben, soll der Linker eine Warnung ausgeben. Im ausführbaren Image sollen die Klassen der Importreihenfolge nach geordnet sein, sodass das Laufzeitsystem die Konstruktoren nacheinander aufrufen kann. Das bietet auch die Möglichkeit, beispielsweise diese Konstruktoren im Supervisor-Modus auszuführen (Konfiguration von Hardware) und anschliessend in den User-Modus zu wechseln. It's important that the heap class and the kernel class are initialized first. For this they are put at the beginning of the list.\\ +Before compilation all top-level classes (also called root classes) can be specified. This list will be parsed from left to right and the imports will be resolved in this order. If there are problems with cyclic imports, the linker will output a warning. In the target image the classes should be ordered in the same manner. The kernel will call the class constructors accordingly. This would allow to call the constructors in the supervisor mode (configuration of hardware) and subsequently change to user mode. \\ 
-In Java ist die Initialisierungsreihenfolge nicht klar definiert. Falls Test auf dem Host und dem Target stets das gleiche Resultat ergeben sollen, bietet sich folgende Lösung an: Im Klassenkonstruktor einer obersten Hauptklasse (die ansonsten vollständig leer ist) werden alle anderen Klassenkonstruktoren aufgerufen. Bei dieser Lösung entfällt auch die Notwendigkeit einer Systemtabelle.+It's important that the heap class and the kernel class are initialized first. For this they are put at the beginning of the list.\\ 
 +Java does not define the order of initialization clearly. If tests on the host and the target should lead to the same result, the following solution would be appropriate: the class constructor of a otherwise empty helper class calls all the other class constructors. This solution would also allow to get rid of the system table.
    
-===== Initialisierung von Objekten ===== +===== Initialization of Objects ===== 
-Die Initialisierung von Objekten wird in den Objektkonstruktoren zusammengefasst.+The initialization of objects is done in the object constructors.
 <code java> <code java>
   int len = 4;  // block 1   int len = 4;  // block 1
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   }   }
 </code> </code>
-Die Objektkonstruktoren heissen alle //init// im Bytecode und unterscheiden sich in der Parameterliste. Block 1 und 2 werden in //init// zusammengefasst. +In the Bytecode these constructors carry the name //init// and vary in the parameter list. Block 1 and block 2 in the above code block will be combined in //init//. 
-Beim Erzeugen eines Objektes wird stets zuerst mit Hilfe von //new// ein Block auf dem Heap alloziert. Anschliessend wird der Konstruktor der Oberklasse aufgerufen (dieser ruft seinerseits den Konstruktor der Oberklasse auf). Diese Aufrufe sind im Bytecode enthalten. +When creating an object a call to //new// allocates a block on the heap. Next, the constructor of the super class is called (which itself calls its super class constructor). These calls can be found in the Bytecode. 
-Klassen dürfen auch Instanzinitialisierer enthalten, z.B. +Classes might also have instance initializers, such as: 
 <code java> <code java>
   int[] data = new int[10];     int[] data = new int[10];  
   {for (int i = 0; i < 10; i++) data[i] = i;}   {for (int i = 0; i < 10; i++) data[i] = i;}
 </code> </code>
-Auch diese Instanzinitialisierer befinden sich im Bytecode in den Objektkonstruktoren.+These initializers go into the object constructors as well.
  
dev/crosscompiler/class_initialization.1415017861.txt.gz · Last modified: 2016/02/25 13:33 (external edit)

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