On Wed, Aug 17, 2005 at 00:59:52 +0100, Adrian Howard wrote: > Sorry - I don't understand. If I do: > > call_to_external_c_library_foo( $foo ); > call_to_external_c_library_bar( $bar ); > > Then how does the compiler know that $foo is only used temporarily and can > be moved around, while $bar is cached in the > external library and shouldn't be moved by any heap de-fragmentation that > the garbage collector might do?
$foo points to the object structure, which also has a "static" handle, that is allocated in a static arena (something that isn't defragmented or copied by the GC). this handle is simply a pointer that points back to the object structure (and is updated as this object moves). The object has it's address, and it has the object's address. When an object is given to a foreign function, that function gets the handle to the object (the address of the staticly located pointer to the dynamically located object). When the compiler is sure that an object is never ever given to an external function, it can omit the code that keeps handles to the objects. This is just a small solution for a GC scheme that copies or defragments - I personally doubt that this will be the case any time in the forseeable future, but it's runtime and GC dependant, and there are other solutions, this is just one. -- () Yuval Kogman <[EMAIL PROTECTED]> 0xEBD27418 perl hacker & /\ kung foo master: /me wields bonsai kittens: neeyah!!!!!!!!!!!!!!!!
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