A segfault on null is fine if the language defines it to be OK (i.e. dereferencing null is reliably a crash), but most environments that allow interacting with

A segfault on null is fine if the language defines it to be OK (i.e. dereferencing null is reliably a crash), but most environments that allow interacting with null (C, C++, LLVM IR) have dereferencing it be undefined behaviour, i.e. the compiler may optimise in ways that mean code that naively results in a null dereference/segfault do not do that and instead result in random memory corruption. Note that Nim uses C as an intermediate language for compilation, so unchecked dereferences of possibly-null pointers are not memory safe.