Hi Jameson, Thank you for your answer,
`primesieve_sieve` is not calling Julia code (juste somme pointer
arithmetics and a delete). But it seems that call to `println` in the
finalizer is causing the error, strangely.
What would be the prefered way to handle memory deallocation in this
case? Copying the result from the C function and immediately deleting
the memory allocated by it would be the easiest way, but it will impact
the performance. Is there any way to avoid that?
Also, I don't know if it's the right explanation, but I have the feeling
that because the GC doesn't know how much memory has been allocated by
the C function, he doesn't know when deallocating memory becomes
"urgent". Is there any way to inform the GC how much memory is hold by a
given pointer?
note, if a c functions returns a bits type (such as Ptr), it is
invalid to declare it to return a struct (such as C_primesieve_array).
this will soon cause failures on the x86 linux ABI.
is the `primesieve_free` c-function itself attempting to execute julia
code?
note, that since you didn't return `primes_ptr`, it will be garbage
collected (and finalized) shortly after your primes function returns
On Sun Feb 08 2015 at 2:15:21 PM <[email protected]
<mailto:[email protected]>> wrote:
Hi guys,
While creating a tiny wrapper over the C/C++ primesieve
<https://github.com/kimwalisch/primesieve> library, I encountered
an error while trying to finalize the Ptr returned by a function.
This pointer must be freed by another function from the library,
so I tried to wrap it into a finalizer function but it doesn't
work because of the following error: "task switch not allowed from
inside gc finalizer". Could someone explain how this could be done
properly? I would try to avoid the returned array if possible.
Here is the code so far:
|
constLIB_PRIMESIEVE ="libprimesieve.so"
type C_primesieve_array
handle::Ptr{Int32}
end
functionprimes(n::Int)
size =Cint[0]
primes_ptr =ccall(
(:primesieve_generate_primes,LIB_PRIMESIEVE),
C_primesieve_array,
(UInt64,UInt64,Ptr{Cint},Int),
1,n,size,3)
functionprimesieve_array_finalizer(primesieve_arr::C_primesieve_array)
ccall(
(:primesieve_free,LIB_PRIMESIEVE),
Void,(Ptr{Int32},),primesieve_arr.handle)
end
finalizer(primes_ptr,primesieve_array_finalizer)
returnpointer_to_array(primes_ptr.handle,size[1],false)
end
|
Thank you very much,
Rémi
