Wait, the compiler can do that? I thought only dereferencing a null pointer gives undefined behavior, just checking if a pointer is 0 or not shold be valid? Ye

Wait, the compiler can do that? I thought only dereferencing a null pointer gives undefined behavior, just checking if a pointer is 0 or not shold be valid? Yeah based on https://joelaro.wordpress.com/2015/09/30/gcc-optimization-fdelete-null-pointer-checks/ https://joelaro.wordpress.com/2015/09/30/gcc-optimization-fd... the assumption is that if the pointer was previously dereferenced, it can be assumed to be non-null, and hence all subsequent null-checks can be elided. Based on https://news.ycombinator.com/item?id=17360772 https://news.ycombinator.com/item?id=17360772, the case in which this actually makes a difference is an address offset like int *n = &param->length The compiler knows the structure so it can just inline the offset, but the optimizer considers this as being non-null.