[Libguestfs] [PATCH v2 1/2] appliance: search all types of appliances for each path separately

[Pavel Butsykin]

> 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#tag_13_47
>
> "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.
>
Excellent, thanks for the clarification.