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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 0x7fe4900838d0
freeing memory at 0x7fe490083f60
freeing memory at 0x7fe490083f40
freeing memory at 0x7fe490083f00
freeing memory at 0x7fe490083ee0
freeing memory at 0x7fe490083ec0
freeing memory at 0x7fe490083f20
freeing memory at 0x7fe490083f80
freeing memory at 0x7fe4900838b0

See also

Ways to use this method:

The source of this document is in /__w/M2/M2/macaulay2-1.26.06+ds/M2/Macaulay2/packages/ForeignFunctions.m2:1818:0.