The complexity argument is just not true. You do have to know this stuff in c++, you run into it all the time.
I wish I didn’t have to know about std::launder but I do
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I wish I didn’t have to know about std::launder but I do
Before C++ added it we relied on undefined behavior that the compilers agreed to interpret in the necessary way if and only if you made the right incantations. I’ve seen bugs in the wild because developers got the incantations wrong. std::launder makes it explicit.
For the broader audience because I see a lot of code that gets this wrong, std::launder does not generate code. It is a compiler barrier that blocks constant folding optimizations of specific in-memory constants at the point of invocation. It tells the compiler that the constant it believes lives at a memory address has been modified by an external process. In a C++ context, these are typically restricted to variables labeled ‘const’.
This mostly only occurs in a way that confuses the compiler if you are doing direct I/O into the process address space. Unless you are a low-level systems developer it is unlikely to affect you.
> 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.
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))));