Storing objects whose size are run-time dependent contiguously in memory

The background I am working on an ECS in C++ for fun and I am trying to make it as efficient as possible. One of the optimisations I am striving to implement is to minimise cache misses by storing the components contiguously in the memory. Since I want to expose the interface to Lua, I cannot use all the compile time goodness C++ offers. The tough part about it is that I don't know the size of the objects at the compile time. As I understand it, I can't just use std::vector and not experience object slicing. TL;DR - The question How do I store objects, whose sizes are known only at runtime, contiguously in the memory? The sizes of the objects in one container are identical.

Feb 15, 2025 - 19:26

The background

I am working on an ECS in C++ for fun and I am trying to make it as efficient as possible. One of the optimisations I am striving to implement is to minimise cache misses by storing the components contiguously in the memory.

Since I want to expose the interface to Lua, I cannot use all the compile time goodness C++ offers. The tough part about it is that I don't know the size of the objects at the compile time. As I understand it, I can't just use std::vector and not experience object slicing.

TL;DR - The question

How do I store objects, whose sizes are known only at runtime, contiguously in the memory? The sizes of the objects in one container are identical.