Question

A chapter out of the book I have been reading has focused on memory management allocating space using malloc linux functions.

Before I read this I would make relatively small programs without allocating space.

Is it acceptable to not do anything in the way of memory allocation for applications whose memory footprint remains under 50MB? What are the repercussions of not doing so?

Answer 1

If you can do without malloc for small applications, you’re probably just not needing to use any heap space. Little utility programs or toy programs often don’t. The things you might be doing wrong though to get by when you should be using the heap are:

1. Arrays. If you find yourself allocating large arrays ‘just to make sure everything fits’ then you should perhaps be using malloc. At the least, handle the error condition that everything overflows to check they really are big enough. With dynamically allocated arrays, you can make bigger ones on the fly if you find you need more space.

2. Doing too much recursion. C benefits from flattening out recursion sometimes into loops over arrays, because unlike function languages it can’t optimise things properly. If you are getting your storage space by calling function lots to create it, that’s pretty dangerous (the program might crash on you one day).

3. Using static pools of objects (structs, classes). Perhaps you have a ring buffer, and 15 objects that could be in it, and you have them statically allocated because you know that your buffer will never have more than 15 entries. That’s kind of OK, but allowing the buffer to grow more by adding in more structs, created with malloc, might be nice.

Probably plenty more situations where programmes which don’t need malloc could benefit from having it added.