From: Rob Landley <rob@landley.net>
To: musl@lists.openwall.com
Cc: musl@lists.openwall.com
Subject: Re: NULL
Date: Sun, 13 Jan 2013 13:46:28 -0600 [thread overview]
Message-ID: <1358106388.32505.17@driftwood> (raw)
In-Reply-To: <20130113174731.GS4468@port70.net> (from nsz@port70.net on Sun Jan 13 11:47:32 2013)
On 01/13/2013 11:47:32 AM, Szabolcs Nagy wrote:
> > So I think you're saying is that the behavior I'm depending on
> changed?
>
> well,
>
> (int)(void*)0 is not an "integer constant expression" and it
> is not a "null pointer constant",
C99 6.3.2.3: An integer constant expression with the value 0, or such
an expression cast to type void *, is called a null pointer constant.
7.17 #3: The macros are NULL which expands to an implementation-defined
null pointer constant;
So it uses "constant" in the name but either it's not a constant or
typecasting it twice makes it stop being a constant.
> it is not an "arithmetic
> constant expression" nor an "address constant", but an
> implementation is allowed to accept it as a "constant expression"
> anyway
> (as far as i can see it is not required to though)
Actually it turned out the problem was I accidentally checked in some
debug code, which set -O0 (which apparently disables --gc-sections even
when explicitly specified).
So it's still working fine. Whether or not it should depends on whether
or not "constant" means it's a constant.
> !(void*)0 and (void*)0 || (void*)0 are similar
>
> in initializers they may be accepted, but the standard
> does not require them to be
At one point, I had to dig through all this stuff:
http://lists.gnu.org/archive/html/tinycc-devel/2007-09/msg00128.html
Alas, that was about 5 years ago and I no longer remember the details.
> gcc used to be less strict integer constant expressions,
> but recently it follows the standard more closely
>
> > Sigh. Yup. When I build toybox with just "true", gcc 4.2.1 (last gpl
> > release) drops out parse_optflag() but the ubuntu host toolchain no
> > longer does.
>
> i think gcc should be able to do the optimization
It can, it was -O0. Pilot error. :)
Rob
next prev parent reply other threads:[~2013-01-13 19:46 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-09 11:02 NULL John Spencer
2013-01-09 12:18 ` NULL Szabolcs Nagy
2013-01-09 13:36 ` NULL John Spencer
2013-01-12 6:32 ` NULL Rob Landley
2013-01-12 6:46 ` NULL Rich Felker
2013-01-12 7:15 ` NULL Luca Barbato
2013-01-12 13:33 ` NULL Rich Felker
2013-01-12 11:39 ` NULL Jens Staal
2013-01-09 13:09 ` NULL croco
2013-01-09 13:47 ` NULL John Spencer
2013-01-09 14:49 ` NULL croco
2013-01-09 14:42 ` NULL Luca Barbato
2013-01-09 14:47 ` NULL Rich Felker
2013-01-09 15:03 ` NULL Luca Barbato
2013-01-09 15:18 ` NULL John Spencer
2013-01-09 15:36 ` NULL Rich Felker
2013-01-09 21:11 ` NULL Rob
2013-01-09 21:53 ` NULL Szabolcs Nagy
2013-01-09 22:17 ` NULL Rob
2013-01-09 23:42 ` NULL Szabolcs Nagy
2013-01-12 6:56 ` NULL Rob Landley
2013-01-12 7:07 ` NULL Bobby Bingham
2013-01-12 13:31 ` NULL Rich Felker
2013-01-13 14:29 ` NULL Rob Landley
2013-01-13 14:56 ` NULL Luca Barbato
2013-01-13 16:29 ` NULL Rob Landley
2013-01-13 17:14 ` NULL Luca Barbato
2013-01-13 15:23 ` NULL Strake
2013-01-13 17:17 ` NULL Luca Barbato
2013-01-13 17:47 ` NULL Szabolcs Nagy
2013-01-13 19:46 ` Rob Landley [this message]
2013-01-14 6:11 ` NULL Rich Felker
2013-01-14 8:45 ` musl as a framework to test applications' compatibility with POSIX (was: NULL) Vasily Kulikov
2013-01-14 14:03 ` Rich Felker
2013-01-14 14:30 ` Vasily Kulikov
2013-01-14 15:02 ` Szabolcs Nagy
2013-01-14 15:14 ` Rich Felker
2013-01-14 13:19 ` NULL Rob Landley
2013-01-12 5:56 ` NULL Rob Landley
2013-01-12 6:42 ` NULL Rich Felker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1358106388.32505.17@driftwood \
--to=rob@landley.net \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).