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From: Samuel Hornus <Samuel.Hornus@inria.fr>
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Subject: [Caml-list] Segfault in C++ stub with many 'new' allocations


Dear all,

I have two questions.

1/ I'm writing a stub to the C++ ANN library [1] to find geometric neighbor=
ing points in space.
The constructor of the main class in this library uses a lot of allocation =
with the "new" C++ keyword.
For small input point sets (e.g. 2500 points), it all seems to work fine.
For larger ones (50 K points), the C++ constructor crashes.
My question is : is it possible that the C++ "new" allocator differs suffic=
iently from the C-style malloc, that bad interactions with OCaml heap happe=
n ?

(I'm passing the input points coordinates in a plain bigarray.)

2/ Regarding bigarray: before using them, I let the C++ constructor access,=
 and keep pointers inside regular OCaml [float array] or [float array array=
]. It was working well (again, for small input point set), but is that safe=
 ? Or can the garbage collector eventually relocate the content of a  [floa=
t array]  or of a [float array array] ? so that the pointer kept in the C++=
 class would become dangling ?

Thank you in advance,
Sam

[1] Approximate Nearest Neighbors http://www.cs.umd.edu/~mount/ANN/=