Is “Out Of Memory” A Recoverable Error?

Question

I\'ve been programming a long time, and the programs I see, when they run out of memory, attempt to clean up and exit, i.e. fail gracefully. I can\'t remember the last time

Answer 1

It depends on what you mean by running out of memory.

When malloc() fails on most systems, it's because you've run out of address-space.

If most of that memory is taken by cacheing, or by mmap'd regions, you might be able to reclaim some of it by freeing your cache or unmmaping. However this really requires that you know what you're using that memory for- and as you've noticed either most programs don't, or it doesn't make a difference.

If you used setrlimit() on yourself (to protect against unforseen attacks, perhaps, or maybe root did it to you), you can relax the limit in your error handler. I do this very frequently- after prompting the user if possible, and logging the event.

On the other hand, catching stack overflow is a bit more difficult, and isn't portable. I wrote a posixish solution for ECL, and described a Windows implementation, if you're going this route. It was checked into ECL a few months ago, but I can dig up the original patches if you're interested.