Question

I’m modifying some C++ source code and I’ve noticed the author really went out of their way to allocate everything on the stack. Most likely for the deallocation benefits (are there any performance benefits as well??).

I want to keep the same consistency but I need to create a large array of objects and something like:

Object os[1000] = {Object(arg), Object(arg), ....};

isn’t going to cut it. Searching around it seems like a way around this is just:

vector<Object> os(1000, Object(arg));

This still allocates on the heap but deallocates like a stack (from what I’ve read in other posts). I’m just wondering are there any other options because this just seems like a syntax issue. Perhaps a clever #define people know.

Answer 1

The stack shouldn’t be used for large blocks of memory. You simply have to pay the higher price of heap allocation in exchange for the benefit of accessing more memory. Another option is declaring an array with static storage duration, but that has other drawbacks (not re-entrant, not thread-safe). Everything is a tradeoff.

In any case, when allocating complex objects, the cost of calling 1000 constructors will dwarf the time spent in the allocator. Just use std::vector unless you have profiler data that shows a performance problem.