[ryao]

I said that GCC defines type punning via unions. It is an extension to the C standard that GCC did.

That said, using “the code compiles in godbolt” as proof that it is not relying on what the standard specifies to be UB is fallacious.

[uecker]

I am a member of the standards committee and a GCC maintainer. The C standard supports union punning. (You are right though that relying on godbolt examples can be misleading.)