Using pointer conversions to store/cast values: Am I breaking the strict aliasing rule?

Question

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Some authoritative users stated that the following code breaks strict aliasing rules.

#include 

        

Answer 1

However, I am never using a pointer to write data [...]

The language in the standard is more general than this; [basic.life]/7 has:

[...] a pointer that pointed to the original object, a reference that referred to the original object, or the name of the original object [...]

In your operator= you're using an lvalue of type T to write to data, and in operator U you're using a pointer of type U to read it; where U and T are unrelated and not character types this is UB.

Just use memcpy. It's guaranteed to work, and it's efficient (try it)!