Re: [Qemu-devel] [PATCH v3 1/6] qemu-option: has_help_option() and is_valid_option_list()

[Kevin Wolf <kwolf@redhat.com>]

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Am 21.02.2014 um 21:22 hat Eric Blake geschrieben:
> On 02/21/2014 08:24 AM, Kevin Wolf wrote:
> > has_help_option() checks if any help option ('help' or '?') occurs
> > anywhere in an option string, so that things like 'cluster_size=4k,help'
> > are recognised.
> > 
> > is_valid_option_list() ensures that the option list doesn't have options
> > with leading commas or trailing unescaped commas.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> 
> > +
> > +    while (*p) {
> > +        p = get_opt_value(buf, buflen, p);
> > +        if (*p) {
> > +            p++;
> > +        }
> > +
> > +        if (is_help_option(buf)) {
> > +            result = true;
> > +            goto out;
> 
> If this were 'break;',
> 
> > +        }
> > +    }
> > +
> > +out:
> 
> then you wouldn't need this label.  But that's cosmetic.
> 
> > +    free(buf);
> > +    return result;
> > +}
> > +
> > +bool is_valid_option_list(const char *param)
> > +{
> > +    size_t buflen = strlen(param) + 1;
> > +    char *buf = g_malloc0(buflen);
> > +    const char *p = param;
> > +    bool result = true;
> > +
> > +    while (*p) {
> > +        p = get_opt_value(buf, buflen, p);
> > +        if (*p && !*++p) {
> > +            result = false;
> > +            goto out;
> > +        }
> 
> Rejects trailing commas.
> 
> > +
> > +        if (!*buf || *buf == ',') {
> 
> Rejects empty options, but also rejects values beginning with a comma.
> But we have legacy users that accept implicitly named first options (see
> opts_do_parse()).  For example, this is a valid command line (albeit one
> that prints a list of valid machines):
> 
> qemu-kvm -machine ,,blah
> 
> as shorthand for
> 
> qemu-kvm -machine type=,,blah
> 
> and where *buf would indeed be validly ','.

Right, but I can't allow this without allowing '-o ,,' which breaks the
real use case. So the lesson is that you can concatenate option strings
and use implicit option names at the same time.

Kevin

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