Re: [RFC PATCH] vsnprintf: Remove use of %n and convert existing uses

[Joe Perches <joe@perches.com>]

On Thu, 2013-09-12 at 08:40 +0900, Tetsuo Handa wrote:
> Joe Perches wrote:
> > -	seq_printf(m, "%s%d%n", con->name, con->index, &len);
> > +	len = seq_printf(m, "%s%d", con->name, con->index);
> 
> Isn't len always 0 or -1 ?

Right.  Well you're no fun...

These uses would seem broken anyway because the
seq_printf isn't itself tested for correctness.

Hmm.

Also, there's a large amount of code that appears
to do calculations with pos or len like:

	pos += seq_printf(handle, fmt. ...)

There are very few that seem to use it correctly
like netfilter.

$ grep -rP --include=*.[ch] "^[ \t]*\S[ \t\S]*\bseq_[v]?printf\b" *

Suggestions?

> int seq_vprintf(struct seq_file *m, const char *f, va_list args)
> {
> 	int len;
> 
> 	if (m->count < m->size) {
> 		len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
> 		if (m->count + len < m->size) {
> 			m->count += len;
> 			return 0;
> 		}
> 	}
> 	seq_set_overflow(m);
> 	return -1;
> }
> EXPORT_SYMBOL(seq_vprintf);
> 
> int seq_printf(struct seq_file *m, const char *f, ...)
> {
> 	int ret;
> 	va_list args;
> 
> 	va_start(args, f);
> 	ret = seq_vprintf(m, f, args);
> 	va_end(args);
> 
> 	return ret;
> }
> EXPORT_SYMBOL(seq_printf);