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[Bug c/22485] pointer +- integer is never NULL
- From: "gdr at integrable-solutions dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 14 Jul 2005 19:38:21 -0000
- Subject: [Bug c/22485] pointer +- integer is never NULL
- References: <20050714131031.22485.mattias@virtutech.se>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- 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