Re: [Xen-devel] [PATCH] cmdline: treat hyphens and underscores the same

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 05/12/2019 16:50, Jan Beulich wrote:
> On 05.12.2019 17:27, Julien Grall wrote:
> > On 05/12/2019 15:33, Jan Beulich wrote:
> > > --- a/xen/common/kernel.c
> > > +++ b/xen/common/kernel.c
> > > @@ -23,6 +23,49 @@ enum system_state system_state = SYS_STA
> > >    xen_commandline_t saved_cmdline;
> > >    static const char __initconst opt_builtin_cmdline[] = CONFIG_CMDLINE;
> > >    
> > > +static int cdiff(unsigned char c1, unsigned char c2)
> > This is not obvious from the name and the implementation what it does
> > (it took me a few minutes to figure it out). So I think you want to add
> > a comment.
> Sure, done.
>
> > > +{
> > > +    int res = c1 - c2;
> > > +
> > > +    if ( res && (c1 ^ c2) == ('-' ^ '_') &&
> > > +         (c1 == '-' || c1 == '_') )
> > > +        res = 0;
> > > +
> > > +    return res;
> > > +}
> > > +
> > > +/*
> > > + * String comparison functions mostly matching strcmp() / strncmp(),
> > > + * except that they treat '-' and '_' as matching one another.
> > > + */
> > > +static int _strcmp(const char *s1, const char *s2)
> > I thought we were trying to avoid new function name with leading _?
> We're trying to avoid new name space violations. Such are
> - identifiers starting with two underscores,
> - identifiers starting with an underscore and an upper case letter,
> - identifiers of non-static symbols starting with an underscore.
I am not sure to understand why non-static symbols only. This would 
prevent you to use the the non-static symbol if you happen to re-use the 
same name.
Anyway, how about calling it cmdline_strncmp()? This would be easier to 
spot misuse on review (i.e using strncmp() rather than _strncmp()).
Cheers,

--
Julien Grall

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