Class declaration

Grammar§

ClassDeclaration ::= Attribute* StorageClass* "class" Identifier InherihanceList? ClassBody InherihanceList ::= ":" Type? | ":" Type ("," Type)* ; ClassBody ::= ";" | "{" Declaration* "}" ;

Semantics§

Classes are the constructs that allow to program using the Object Oriented paradigm.

Attributes§

See Attribute for a list of the attributes allowed on class declarations.

Inheritance list§

Classes can only inherits of a single Type that must itself resolved to a ClassDeclaration.

ABI§

The layout of a class consists of

The type of a virtual table is a pointer to a static array of pointer.

The first pointer is a pointer to the super virtual table (or null). It allows to perform dynamic casts, i.e from less specialized to more specialized but also to call the previous implementation of a virtual method, as required by the SuperExpression.

The following pointers are the addresses of the most overridden virtual functions known by the instance.

Allocation§

Because they have a virtual table, pointer to classes may not be manually allocated. Instead the NewExpression must be used with a custom allocator, which also permit to copy the virtual table.

class C
{
    @constructor function create() {}
    @destructor function destroy() {}
}

function test()
{
    C* c_on_heap = (new C).create(); // `new C` propers init the vtable
    C c_on_stack1 = C.create();      // vtable init correctly because of the constructor called as value constructor
    C c_on_stack2;                   // vtable init correctly as per deafault init rules

    // at end of scope
    // - c_on_stack1.destroy() called automatically
    // - c_on_stack2.destroy() called automatically
    // - c_on_heap continues to live
}