From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: NULL
Date: Sat, 12 Jan 2013 01:42:54 -0500 [thread overview]
Message-ID: <20130112064254.GF20323@brightrain.aerifal.cx> (raw)
In-Reply-To: <1357970162.32505.3@driftwood>
On Fri, Jan 11, 2013 at 11:56:02PM -0600, Rob Landley wrote:
> On 01/09/2013 05:02:29 AM, John Spencer wrote:
> >glibc defines NULL as __null: a magic variable supplied by GCC and
> >compatibles which always has pointer context.
> >
> >musl defines NULL to 0 in C++.
> >this is correct per the standard, but breaks a lot of software on
> >64bit archs,
> >because it promotes to int.
>
> The C99 standard section 7.17 defines the NULL macro as:
>
> expands to an implementation-defined null pointer constant
>
> Which means it has pointer type. So either we can typecast it to
Nope, C is weirder than you think. A "null pointer constant" is
defined as an integer constant expression with value zero, or such an
expression cast to void *. So it need not have pointer type.
> void *, or we can rely on the LP64 standard (Linux, FreeBSD, and
> macosX all support) which says that long and pointer are always the
> same size on both 32 bit and 64 bit, so trivial fix would be #define
> NULL to (0L)
Yes, using 0L on both C and C++ is the solution I'm leaning towards..
Rich
prev parent reply other threads:[~2013-01-12 6:42 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 ` NULL Rob Landley
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 ` Rich Felker [this message]
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