Pointers to entities go bad after a while, C++ vector
std::vector<Entity> entities; and the enemies keep an Entity* target. After some spawns, target points to garbage, and it crashes only sometimes. Valgrind says invalid read. Is it because vector moved?
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Yes. push_back reallocates when it runs out of capacity, and all your pointers point into the old buffer. It's the same reason Rust refuses the code in tomasz's thread, /progrider/t/AhtK41Hy5_6g, except here it compiles and you get to find out at runtime.
Say it louder.
Fixes, in the order I'd try them: store an index or a handle in place of a pointer. std::deque if you only add at the ends, its references stay valid on push_back. Calling reserve() up front hides the bug until you exceed it.
Went with index + generation number, so a stale handle gets detected instead of pointing at the wrong enemy. Works well. Thanks, and ferrous, no.
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