Fix passing nullptr to args marked as non-null

libstdc++'s |memcpy| and |memset| both state that their inputs should
never be a nullptr since this matches the C spec. Some compilers act on
these hints, so we shouldn't unconditionally call these as it would
signal to the compiler that they can't be nullptrs.

As an example, the following code will always call |do_something()|
when compiled with optimisations since GCC version 4.9:
```
    void clear(void *ptr, int size) {
        memset(ptr, 0, size);
    }
    void example(void *ptr, int size) {
        clear(ptr, size);
        if (ptr != nullptr) do_something();
    }
```

0 files changed, 0 insertions, 0 deletions