So you expect the compiler to tell you every time it inlines a function with a null check in a function which already had a null check on the same value?

Because as far as it’s concerned that is the same thing.

Both clang-tidy and sonar will flag this since it’s broken on its own, but when you’ve fixed it you want the compiler to warn you every time this is inlined in a function where b is known non-zero and the check is redundant?

As flo told you, if you want a non-optimizing compiler use a non-optimizing compiler.