[Cryptography] bounded pointers in C

[Patrick Chkoreff]

Nemo wrote, On 04/21/2014 12:46 PM:

> So you are not reading the standard. You are reading the manual for a
> particular C compiler on a particular system that no longer exists.
> 
> The C standard looks more like this:
> 
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf

Excellent, good point, thank you.


> See section 6.3.2.3 paragraphs (5) and (6) and section 7.20.1.4.

Yes, and I see that intptr_t is optional, so the only really portable
way to do what I'm talking about is to bite the bullet and use a union,
e.g.:

  union
      {
      unsigned long N;
      void *P;
      };

I'm also replacing overflow checks with truly portable versions, along
the lines of:

  unsigned int x = ...;
  unsigned int y = ...;

  assert(x <= UINT_MAX - y);
  unsigned int z = x + y;

Fortunately all references to such details are confined to a *very* few
points in my code.


-- Patrick