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SubjectRe: [PATCH 1/2] tracing/events: clean up for ftrace_set_clr_event()

On Fri, 8 May 2009, Frederic Weisbecker wrote:
> >
> > -static int ftrace_set_clr_event(char *buf, int set)
> > +/*
> > + * __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
> > + */
> > +static int __ftrace_set_clr_event(const char *match, const char *sub,
> > + const char *event, int set)
> > {
> > struct ftrace_event_call *call;
> > + int ret;
> > +
> > + mutex_lock(&event_mutex);
> > + list_for_each_entry(call, &ftrace_events, list) {
> > +
> > + if (!call->name || !call->regfunc)
> > + continue;
> > +
> > + if (match &&
> > + strcmp(match, call->name) != 0 &&
> > + strcmp(match, call->system) != 0)
> > + continue;
> > +
> > + if (sub && strcmp(sub, call->system) != 0)
> > + continue;
> > +
> > + if (event && strcmp(event, call->name) != 0)
> > + continue;
>
>
> Neat: You can simply use !strcmp(...)

Hehe, no he can't. It would be "strcmp(...)" for the true case. This is
exactly why I prefer to use "strcmp(...) != 0" over "!strcmp(...)".
Because, like you, I've confused "!strcmp(...)" too many times as "not a
match" when it in fact means "is a match".

I've made this mistake enough that I've given up on using just "strcmp" or
"!strcmp". "strcmp() != 0" and "strcmp() == 0" show what you want much
better.

-- Steve



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