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

Out of memory normally means you have to quit whatever you were doing. If you are careful about cleanup, though, it can leave the program itself operational and able to respond to other requests. It's better to have a program say "Sorry, not enough memory to do " than say "Sorry, out of memory, shutting down."

Answer 2

I have this:

void *smalloc(size_t size) {
  void *mem = null; 
  for(;;) {
   mem = malloc(size);
   if(mem == NULL) {
    sleep(1);
   } else 
     break;
  }
  return mem;
}

Which has saved a system a few times already. Just because you're out of memory now, doesn't mean some other part of the system or other processes running on the system have some memory they'll give back soon. You better be very very careful before attempting such tricks, and have all control over every memory you do allocate in your program though.

Answer 3

This is a difficult question. On first sight it seems having no more memory means "out of luck" but, you must also see that one can get rid of many memory related stuff if one really insist. Let's just take the in other ways broken function strtok which on one hand has no problems with memory stuff. Then take as counterpart g_string_split from the Glib library, which heavily depends on allocation of memory as nearly everything in glib or GObject based programs. One can definitly say in more dynamic languages memory allocation is much more used as in more inflexible languages, especially C. But let us see the alternatives. If you just end the program if you run out of memory, even careful developed code may stop working. But if you have a recoverable error, you can do something about it. So the argument, making it recoverable means that one can choose to "handle" that situation differently (e.g putting aside a memory block for emergencies, or degradation to a less memory extensive program).

So the most compelling reason is. If you provide a way of recovering one can try the recoverying, if you do not have the choice all depends on always getting enough memory...

Regards

Answer 4

Users of MATLAB run out of memory all the time when performing arithmetic with large arrays. For example if variable x fits in memory and they run "x+1" then MATLAB allocates space for the result and then fills it. If the allocation fails MATLAB errors and the user can try something else. It would be a disaster if MATLAB exited whenever this use case came up.

Answer 5

It is recoverable only if you catch it and handle it correctly.

In same cases, for example, a request tried to allocate a lot memory. It is quite predictable and you can handle it very very well.

However, in many cases in multi-thread application, OOE may also happen on background thread (including created by system/3rd-party library). It is almost imposable to predict and you may unable to recover the state of all your threads.

Answer 6

Especially in garbage collected environments, it's quote likely that if you catch the OutOfMemory error at a high level of the application, lots of stuff has gone out of scope and can be reclaimed to give you back memory.

In the case of single excessive allocations, the app may be able to continue working flawlessly. Of course, if you have a gradual memory leak, you'll just run into the problem again (more likely sooner than later), but it's still a good idea to give the app a chance to go down gracefully, save unsaved changes in the case of a GUI app, etc.