Re: [Xen-devel] [PATCH v6 for-4.5 4/5] xl: add 'trim' and 'split_string_into_pair' functions

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 26, 2014 at 04:45:30PM +0100, Ian Jackson wrote:
> Wei Liu writes ("Re: [PATCH v6 for-4.5 4/5] xl: add 'trim' and 
> 'split_string_into_pair' functions"):
> > On Wed, Sep 24, 2014 at 09:48:04PM +0100, David Scott wrote:
> > > +/* NB: this follows the interface used by <ctype.h>. See 'man 3 ctype'
> > > +   and look for CTYPE in libxl_internal.h */
> > > +typedef int (*char_predicate_t)(const int c);
> > > +
> > > +static void trim(char_predicate_t predicate, const char *input, char 
> > > **output) __attribute__ ((unused));
> > > +static void trim(char_predicate_t predicate, const char *input, char 
> > > **output)
> > > +{
> > > +    char *p, *q, *tmp;
> > 
> > Ideally you should check input != NULL before dereferencing it. Or you
> > need to document this function expects a valid pointer.
> 
> (Thanks for looking at this, Wei, but:)
> 
> I disagree.  I think in general a function that takes any kind of
> pointer should be assumed to require a non-NULL pointer.  It should
> not carry out any kind of nullness check; it should just dereference
> the pointer (and consequently crash if it is NULL).
> 
> If a function permits callers to pass NULL, that should be documented
> in the function's doc comment (along, presumably, with the semantics,
> if that isn't obvious).
> 

Fair enough. I don't really have strong preference on this kind of
issue. We just need to have an agreement on which route we take. 

Wei.

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