Thread: strange compiler

Originally Posted by Salem

VLA's are essentially useless candy IMO.

The biggest problem is what happens if your VLA no longer fits on the stack (assuming that is where VLAs get created on a given machine). Even the best scenario results in the program being killed by the OS. On an embedded system, it probably just trashes someone else's memory. Nor is there a way of finding out in advance whether it will succeed or not, just close your eyes, pray and take a jump.

Of course, a lot of naive programmers are going to take unchecked user input, and create their VLA directly from that. Most of them won't even bother to check for negative numbers, nevermind huge positive numbers.

At least with malloc, there is a clearly defined way of being told there is no more room, and from there you can take appropriate action.

Yes all true, but it has a place. If you need scratch memory allocated dynamically it can be quite convenient. For example if I'm doing a bunch of matrix operations, or even a bunch of rotations using quaternions for graphics applications, I'd like to be able to allocate some temp memory of small but possibly unknown size; use it for my calculations and then discard it.

I suppose also, if you want to get a little more sophisticated you can try to increase your stack size. I know how to do that in assembly language, but I'm not sure about the various C compilers. Microsoft no doubt has some pragmas that support it and maybe gcc does to. Unfortunately MS has decided in recent versions of their compilers that inline assembly is simply not necessary any more.