[dezgeg]

In huge number of cases the null dereference is not from accessing 0x0 but some offset to it (ie. accessing a struct member or array element that's not the first one). Of course in practice most of the offsets are below the limit where nothing is ever mapped (on Linux vm.mmap_min_addr and seems 64k by default for me) but it's still very possible to have such dereference to not segfault in C. That should not be possible in Go/Java (if it is, it would almost certainly be considered a bug in the compiler/VM).

[trealira]

Why isn't it possible in Go? If you can use pointers to structures in both Go and C, and you can access the fields of a structure through a pointer in both, then I don't understand why reading a structure field through a null pointer wouldn't cause the dereference of an address like 0x8 in both languages.

[dezgeg]

Unbounded/large offsets are the critical part. Minimum unit where memory protection can be set is one page (4096 bytes on x86), so compiler could reasonably assume that offsets 0-4095 are always safe to dereference (in the sense that SIGSEGV is guaranteed, which can be then turned into a NullPointerException in the SIGSEGV signal handler) without a NULL check. For anything larger or array accesses, add a explicit check for NULL before dereference.