runtime-undefined behavior in the C++ standard

In section 3.50 of the latest draft of the C++ standard, there is this definition:

What is the precise relationship between C and it’s abstract machine?

I am reading “C in a nutshell” and there are alot of sentences similar to this one:

no match for ‘operator==’ in GCC 12

When I compiled the code below using GCC 12, I encountered an error saying "no match for 'operator=='", but the code compiles fine with GCC 11.

Why is std::bit_cast allowed on pointers?

std::bit_cast is advertised as the safe alternative to type-punning via reinterpret_cast. However, I see very often that people just blindly replace reinterpret_cast with bit_cast and calls it a day:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example:

where are the standard rules that can interpret the issue of the wrong check in `std::shared_ptr`

Consider this example: