It's obvious at the langauge level if you are creating, for example, an int pointer that is not guaranteed to be int-aligned. The only way to guarantee that an int pointer is int-aligned is if it comes from malloc* or new (C++), or if you take the address of an integer variable.

Any time you need to use a type cast to assign an int pointer, other than casting the output of malloc, then you potentially have a unaligned pointer, although only the compiler, knowing the alignment requirements of the target, would know if that is creating an invalid pointer or not.

* The C/C++ language (standard library) spec says that malloc must return memory that is aligned to meet the (target) requirements of all built in types, which is obviously a bit wasteful, as well not helpful for things like SIMD types that may be supported by libraries rather than built-in.