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Basic support for classes, interfaces and instance methods. This is implemented by adding a new linkage attribute, `Objective-C`, and a compiler recognized UDA, `@selector`. The linkage attribute is to be used on a class or interface. The UDA is attached to a method. The linkage attribute tells the compiler that the class should use the name mangling that matches the one used by Objective-C (same as C, no mangling) and that all methods in the class should use the Objective-C way of calling methods, see below. The calling convention for Objective-C methods and functions is the same as for C. The selector UDA tells the compiler what Objective-C selector the method should have. The selector is used in the Objective-C runtime to find the implementation of a given method. An Objective-C method call is implemented by making a regular C call to the `objc_msgSend` function in the Objective-C runtime. The signature of `objc_msgSend` looks something like this: `id objc_msgSend(id self, SEL op, ...);` * The first parameter is the object (this/self pointer) * The second parameter is the selector attached to the method * The last parameter is for all the arguments that the implementation expects The call to `objc_msgSend` should not be performed as a variadic call but instead as if it had the same signature as the method that should be called but with the two additional parameter, `self` and `op`, added first. The implementation of `objc_msgSend` will jump to the method instead of calling it. Because of the above, multiple versions exist of `objc_msgSend`. Depending on the return type of the method that is called the correct version need to be used. This depends on the ABI. This is a list of functions and for which types they're used on OS X 64bit: * objc_msgSend_stret - Used for structs too large to be returned in registries * objc_msgSend_fpret - Used for `long double` * objc_msgSend_fp2ret - Used for `_Complex long double` * objc_msgSend - Used for everything else
3 lines
58 B
D
3 lines
58 B
D
// EXTRA_OBJC_SOURCES
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extern (Objective-C) void NSLog();
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