Do you see all the concepts you had to describe here?
> Unless you are a low-level systems developer it is unlikely to affect you.
Making new data structure is common. Serializing classes into buffers is common.
> Unless you are a low-level systems developer it is unlikely to affect you.
Making new data structure is common. Serializing classes into buffers is common.
std::launder is a tool for object instances that magically appear where other object instances previously existed but are not visible to the compiler. The typical case is some kind of DMA like direct I/O. The compiler can’t see this at compile time and therefore assumes it can’t happen. std::launder informs the compiler that some things it believes to be constant are no longer true and it needs to update its priors.
Std::vector needs launder.
You don't want std::launder for any of that. If you must create object instances from random preexisting bytes you want std::bit_cast or https://en.cppreference.com/w/cpp/memory/start_lifetime_as.h...
return std::launder(static_cast<T*>(std::memmove(p, p, sizeof(T))));