Re: Is the Ada run-time required to detect out-of-memory conditions?

[Duncan Sands <baldrick@free.fr>]

> I'm very new to Ada, but I'm impressed of all the features. In parallel
> I'm developing a little library to make C programming easier. In this
> library I malloc'ed some "emergency memory" at the program start which
> is simply freed when the process gets out of memory. Then the error
> handler can at least raise an exception or print some warning.

This will not work on some operating systems (such as linux).  They don't
actually allocate the memory until you access it (in particular this means
that malloc never fails).  So you would (at least) need to fill the memory
with something after allocating it, to be sure you were really assigned some
memory.  But even so, the memory is liable to be swapped out to disk after
a while (because the OS will notice that you are not using it).  So freeing it
won't in fact give you any more memory, because that memory area is probably
already being used for something else.  And if the OOM killer (linux specific)
decides to kill you, then your program is instantly dead and you will have no
chance of freeing memory, or doing anything else for that matter.

Ciao,

Duncan.