[PATCH weston v4 2/9] libweston: add weston_debug API and implementation

[Daniel Stone]

Hey,

On 23 October 2017 at 12:54, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> On Mon, 23 Oct 2017 12:34:47 +0200
> Daniel Stone <daniel at fooishbar.org> wrote:
>> On 12 October 2017 at 13:13, Emre Ucan <eucan at de.adit-jv.com> wrote:
>> > +       gettimeofday(&tv, NULL);
>> > +
>> > +       bdt = localtime(&tv.tv_sec);
>> > +       if (bdt)
>> > +               ret = strftime(string, sizeof string,
>> > +                              "%Y-%m-%d %H:%M:%S", bdt);
>> > +
>> > +       if (ret > 0)
>> > +               snprintf(buf, len, "[%s.%03ld][%s]", string,
>> > +                        tv.tv_usec / 1000, scope->name);
>> > +       else
>> > +               snprintf(buf, len, "[?][%s]", scope->name);
>>
>> I would very much not like to see formatted time in the debug scopes.
>> Can we please just use a raw microsecond value? Ultimately I would
>> like to see tools parse these files, but trying to parse formatted
>> times is a nightmare.
>
> Hm, that is very much contrary to my original intentions. I hate
> reading raw timestamps, they are difficult to make sense of. I also
> didn't intend the output to be machine-parsed, at least not the streams
> that use this function for timestamps. (Emitting timestamps is
> completely optional.)
>
> The usual use case for these is that I am reading through the log
> myself and that is what I optimized for: human readability.
>
> I suppose we would need a dual-mode framework to support both
> human-readable and machine-readable output, because I cannot see myself
> updating a post-processing parser every time I add some new debug prints.
>
> This is literally supposed to be a dynamic printf equivalent.

I totally get your point, but on the other hand, we need a specialist
client to capture the messages anyway. So why not enforce that every
line begins with usec followed by a space (or, if a continuation,
newline directly followed by a space)? It's trivial for a
printf-stream tool to convert, but also makes it more usable for tools
which want to interpret the output a bit better.

Cheers,
Daniel