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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 0x75b96407fe70
freeing memory at 0x75b96407fe30
freeing memory at 0x75b96407fe50
freeing memory at 0x75b96407fdf0
freeing memory at 0x75b96407fe10
freeing memory at 0x75b96407fdb0
freeing memory at 0x75b96407f710
freeing memory at 0x75b96407f6f0
freeing memory at 0x75b96407fdd0

See also

Ways to use this method:

The source of this document is in /build/macaulay2-tiVLjc/macaulay2-1.25.11+ds/M2/Macaulay2/packages/ForeignFunctions.m2:1807:0.