[Bug c/22485] pointer +- integer is never NULL

[gdr at integrable-solutions dot net]

------- Additional Comments From gdr at integrable-solutions dot net  2005-07-14 19:38 -------
Subject: Re:  pointer +- integer is never NULL

"falk at debian dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| ------- Additional Comments From falk at debian dot org  2005-07-14 15:37 -------
| (In reply to comment #7)
| 
| > I'm failing to find anything in the C++ standard that suggests that the
| > following shall be undefined
| > 
| >    (reinterpret_cast<int*>(0) + 5) - 5
| 
| If (reinterpret_cast<int*>(0) + 5) - 5 is not undefined, then neither is
| reinterpret_cast<int*>(0) + 5. Then what is its result, by which paragraph
| in the standard?

The standard says that the mapping used by reinterpret_cast to turn an
integer into a pointer is *implemented-defined*.  It is not undefined.
GCC uses the "obvious" mapping, which is reinterpret_cast<int*>(0) is
the null pointer.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22485