Re: Start a Windows process and get its text output

["Hibou57 (Yannick Duchêne)" <yannick_duchene@yahoo.fr>]

As it is the subject here : I've just checked at least with GNAT it
work nice to create a task, invok a CreateProcess from this Ada task
and then WaitForSingleObject with delay INFINITE on the process handle
always in the same Ada task : other Ada task are still running
normally (a protected object can then be used to tell any other task
the process has terminated).

I was wondering about the cost of threads on Windows, as GNAT create
Ada task as Windows thread (I suppose its the same for Janus and
others, I hope to be honest). I just found there is a default
allocated stack of 1M bytes, and nothing about the cost of task
creation and task switch in CPU cycles (from a pure point of view,
dropping any page fault and the like). If someone know a good source
about it, it would be nice (this is to weigh up the choice to have an
Ada task per process vs. a single Ada task managing multiple
processes).

The sole words about it in the MS reference says :
> The number of threads a process can create is limited by the
> available virtual memory. By default, every thread has one megabyte
> of stack space. Therefore, you can create at most 2028 threads. If
> you reduce the default stack size, you can create more threads.
> However, your application will have better performance if you create
> one thread per processor and build queues of requests for which the
> application maintains the context information. A thread would
> process all requests in a queue before processing requests in the
> next queue.

While the thread (then Ada task) stack size can be tuned with the
Storage_Size attribute, while formally speaking, as of [ARM 13.1(60)],
this is not strictly the stack size, but rather a size including the
stack size. And this attribute is marked as obsolescent in [ARM J.6],
in favor of the pragma which as the same name.