c++ - Can std::uintptr_t be used to avoid undefined behavior of out-of-bounds pointer arithmetic? -

now know doing out-of-bounds-pointer-arithmetic has undefined behavior described in so question.

my question is: can workaround such restriction casting std::uintptr_t arithmetic operations , cast pointer? guaranteed work?

for example:

char a[5]; auto u = reinterpret_cast<std::uintptr_t>(a) - 1; auto p = reinterpret_cast<char*>(u + 1); // ok? 

the real world usage optimizing offsetted memory access -- instead of p[n + offset], want offset_p[n].

edit make question more explicit:

given base pointer p of char array, if p + n valid pointer, reinterpret_cast<char*>(reinterpret_cast<std::uintptr_t>(p) + n) guaranteed yield same valid pointer?

yes, legal, must reinterpret_cast same uintptr_t value char*.

(therefore, you're intending illegal; is, converting different value pointer.)

5.2.10 reinterpret cast

4 . pointer can explicitly converted integral type large enough hold it. mapping function implementation-defined.

5 . value of integral type or enumeration type can explicitly converted pointer. pointer converted integer of sufficient size (if such exists on implementation) , same pointer type have original value;

(note there'd no way, in general, compiler know subtracted 1 , added back.)