alt Hacker NewsSure, but none of that is relevant to just the code snippet that was posted. The compiler can exploit UB in other code to do weird things, but that's just C being C. There's nothing unexpected in the snippet posted.
The issue is cause by C declaring that dereferencing a null pointer is UB. It's not really an issue with assertions.
You can get the same optimisation-removes-code for any UB.
> There's nothing unexpected in the snippet posted.
> The issue is cause by C declaring that dereferencing a null pointer is UB. It's not really an issue with assertions. > You can get the same optimisation-removes-code for any UB.
I disagree - It’s a 4 line toy example but in a 30-40 line function these things are not always clear. The actual problem is if you compile with NDEBUG=1, the nullptr check is removed and the optimiser can (and will, currently) do unexpected things.
The printf sample above is a good example of the side effects.