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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 0x7728f007fe50
freeing memory at 0x7728f007fe30
freeing memory at 0x7728f007fdd0
freeing memory at 0x7728f007f6f0
freeing memory at 0x7728f007fe10
freeing memory at 0x7728f007fdf0
freeing memory at 0x7728f007fe70
freeing memory at 0x7728f007fdb0
freeing memory at 0x7728f007f710

See also

Ways to use this method:

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/ForeignFunctions.m2:1807:0.