如果 malloc 返回 NULL 怎么办？

Question

in my program I work with big amount of data. I use the malloc() function to allocate memory for my large array. After I allocate the memory, I check if the pointer is NULL (that's because there isn't that big memory space or I don't know why).

But sometimes my pointer is NULL. So now what to do? I made a loop, that tries to allocate it again and again if the pointer is NULL. But it becomes to an infinite loop and it still says, that the pointer is NULL. So how to allocate the memory if it doesn't want to?

Thank you for your responses.

Answer 1

It depends on the criticality of the memory you try to allocate:

• if the program can't run without it, just log the error and shutdown;
• if the program can run without it, and if it makes sense to run in degraded mode, log the error, drop the treatment and continue hoping for the best.

Answer 2

If malloc fails then you have run out of available memory. There is no point in calling it again with the same requested size. It will continue to fail until you release some of your allocated memory using free .

Answer 3

If you are working on an embedded system that has limited memory, good chances are that the malloc() returned a NULL because you were attempting to request more memory than it had free (in one contiguous block). Without knowing more implementation details, or the size of malloc() request, I cannot speculate about why this was.

However, it does point to the fact that you have to understand the memory utilization of your solution, so that you can determine what memory is being used where, and determine how you can free memory that might be in use, or if you have to move to a system design with more system memory.