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registerFinalizer(ForeignObject,Function) -- register a finalizer for a foreign object

Description

If a foreign pointer object corresponds to memory that was not allocated by the GC garbage collector, then a function to properly deallocate this memory when the Pointer object that stores this pointer is garbage collected should be called. The function should take a single argument, a foreign object, typically of type voidstar, which corresponds to the memory to deallocate.

i1 : malloc = foreignFunction("malloc", voidstar, ulong)

o1 = malloc

o1 : ForeignFunction
 
i2 : free = foreignFunction("free", void, voidstar)

o2 = free

o2 : ForeignFunction
 
i3 : finalizer = x -> (print("freeing memory at " | net x); free x)

o3 = finalizer

o3 : FunctionClosure
 
i4 : for i to 9 do (x := malloc 8; registerFinalizer(x, finalizer))
 
i5 : collectGarbage()
freeing memory at 0x3ff20080bc0
freeing memory at 0x3ff20080b80
freeing memory at 0x3ff20080c40
freeing memory at 0x3ff20080c00
freeing memory at 0x3ff20080be0
freeing memory at 0x3ff20080b60
freeing memory at 0x3ff200805d0
freeing memory at 0x3ff200805f0
freeing memory at 0x3ff20080c20
freeing memory at 0x3ff20080ba0

See also

Ways to use this method:

The source of this document is in ForeignFunctions.m2:1812:0.