One way is to allocate first. alloca(1GB) typically isn't going to cause a SEGV, so you can check the allocation after making it. With VLAs you have to make s

One way is to allocate first. alloca(1GB) typically isn't going to cause a SEGV, so you can check the allocation after making it. With VLAs you have to make sure (this is not portable) that the compiler will put your loop iterator state variables ahead of the VLA. If you can assume a linear stack (which is kinda the whole point of this discussion) then you can call a function that will repeatedly alloca() in small chunks and touch a byte and return on success or SEGV on failure, and then when it returns it will release that memory but then you know you can safely alloca() that much.