Re: [Libguestfs] [PATCH v2 1/2] appliance: search all types of appliances for each path separately
On 05/05/2017 12:18 PM, Eric Blake wrote:
On 05/05/2017 12:07 PM, Richard W.M. Jones wrote:
> Eric, what do you think of Pavel's analysis and/or suggested fix
> below? It seems all too plausible to me unfortunately :-(
>
>> There NULL is macros which can be defined as 0 or (void*)0, again in
>> accordance with c99:
C99 permits:
#define NULL 0
but POSIX does not. POSIX _requires_
#define NULL ((void*)0)
or the equivalent, so that NULL is properly typed as a pointer to void
in ALL cases (rather than the weaker C99 solution of letting the integer
zero constant leak), in part _because_ of the commonality of passing
NULL through varargs functions.
I forgot to cite my reference:
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html#ta...
"NULL
Null pointer constant. [CX] [Option Start] The macro shall expand
to an integer constant expression with the value 0 cast to type void *.
[Option End]"
...
"RATIONALE
The ISO C standard does not require the NULL macro to include the
cast to type void * and specifies that the NULL macro be
implementation-defined. POSIX.1-2008 requires the cast and therefore
need not be implementation-defined."
where the CX option represents requirements that POSIX makes
above-and-beyond bare C99.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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