Re: Controlled types for resource locking

[tmoran@bix.com]

>I have some code in which I'm protecting a hardware resource using a
>protected type. It's getting quite a mess at the moment with lock/unlocks
>all over the place - especially where exception handlers get involved. I'm
  You can make a controlled type whose Initialize grabs the lock and
whose Finalize releases it, then declare an object of this controlled
type as the first thing in any subprogram (or block) that needs access
to the hardware.  Thus you can't execute code inside the subprogram
till the Initialize has been called, and you own the resource.  Any way
you leave the subprogram, you are guaranteed the Finalize will release
the resource.
  p.s.  There was a bug in a compiler I used a year or so ago, and
which I believe has since been fixed, such that Finalize would be
called even if Initialize had failed (raised a Cant_Get_Resource
exception, for instance).  Make sure nothing like that is happening
with your system.