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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/97976] Optimization relating to NULL pointer assumptions in gcc 9.1
Date: Thu, 26 Nov 2020 00:20:26 +0000	[thread overview]
Message-ID: <bug-97976-4-59x38DA1Iw@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-97976-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97976

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---

6.3.2.3 p3 says a null pointer compares unequal to any pointer to an object, so
that means no object can ever be at address 0 in a valid C program. If you're
not using the -fno-delete-null-pointer-checks option then GCC is perfectly
justified to assume no object is at address 0 (because the standards say that's
not possible).

The footnote on 6.5.3.2 clarifies that a null pointer is not a valid operand
for the unary * operator. 

For C++, [basic.compound] says a pointer can point to an object or be null, not
both.

  parent reply	other threads:[~2020-11-26  0:20 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-24 22:08 [Bug c++/97976] New: Optimization regression in 10.1 for lambda passed as template argument peter at int19h dot net
2020-11-24 22:14 ` [Bug c++/97976] " pinskia at gcc dot gnu.org
2020-11-24 22:24 ` peter at int19h dot net
2020-11-25  4:40 ` peter at int19h dot net
2020-11-25  8:25 ` [Bug c++/97976] Optimization relating to NULL pointer assumptions in gcc 9.1 rguenth at gcc dot gnu.org
2020-11-25 16:43 ` peter at int19h dot net
2020-11-25 18:18 ` redi at gcc dot gnu.org
2020-11-25 19:46 ` peter at int19h dot net
2020-11-25 23:55 ` redi at gcc dot gnu.org
2020-11-26  0:20 ` redi at gcc dot gnu.org [this message]
2020-11-26  1:37 ` peter at int19h dot net
2020-11-26 10:08 ` redi at gcc dot gnu.org
2020-11-26 10:09 ` redi at gcc dot gnu.org

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