On Fri, Nov 06, 2015 at 05:22:27PM +0000, Bruce Richardson wrote:
> On Fri, Nov 06, 2015 at 05:10:07PM +0000, Bruce Richardson wrote:
> > On Thu, Nov 05, 2015 at 04:09:18PM +0100, Adrien Mazarguil wrote:
> > >
> > > I won't argue against this as it's obviously more complex than the
> > > original
> > > method, however note that users of the RTE_PMD_DEBUG_TRACE() macro do not
> > > have to modify their code. They shouldn't care about the implementation.
> > >
> > > Also note that we can do much cleaner code if we drop the all macros
> > > implementation using a (much easier to debug) static inline function,
> > > only perhaps with a wrapper macro that provides __LINE__, __func__ and
> > > __FILE__ as arguments. Nontrival code shouldn't be done in macros anyway.
> > >
> > Getting something working with __FILE__ and probably __LINE__ would be easy
> > enough
> > with a helper macro, but __func__ is not so easy as it's not a preprocessor
> > symbol
> > [since the pre-processor has no idea what function you are in].
> >
> > However, using func, here is the best I've come up with so far. It's not
> > that
> > pretty, but it's probably easier to work with than the macro version.
> >
> > #ifdef RTE_LIBRTE_ETHDEV_DEBUG
> > -#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> > - RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args)
> > +#define RTE_PMD_DEBUG_TRACE(...) \
> > + rte_pmd_debug_trace(__func__, __VA_ARGS__)
> > +
> > +static inline void
> > +rte_pmd_debug_trace(const char *func_name, const char *fmt, ...)
> > +{
> > + static __thread char buffer[128];
> > + char *out_buf = buffer;
> > + unsigned count;
> > + va_list ap;
> > +
> > + count = snprintf(buffer, sizeof(buffer), "%s: %s", func_name, fmt);
> > + if (count >= sizeof(buffer)) { // truncated output
> > + char *new_buf = malloc(count + 1);
> > + if (new_buf == NULL) // no memory, just print 128 chars
> > + goto print_buffer;
> > + snprintf(new_buf, count + 1, "%s: %s", func_name, fmt);
> > + va_start(ap, fmt);
> > + rte_vlog(RTE_LOG_ERR, RTE_LOGTYPE_PMD, buffer, ap);
> > + va_end(ap);
> > + free(new_buf);
> > + return;
> > + }
> > +
> > +print_buffer:
> > + va_start(ap, fmt);
> > + rte_vlog(RTE_LOG_ERR, RTE_LOGTYPE_PMD, out_buf, ap);
> > + va_end(ap);
> > +}
> > #else
> > #define RTE_PMD_DEBUG_TRACE(fmt, args...)
> > #endif
> >
> > Comments or improvements?
Such a function shouldn't malloc() anything. The entire line should fit on
the stack (crashing is fine if it does not, then it's probably a bug). We
did something in two passes along these lines in mlx5_defs.h (not pretty but
quite useful):
/* Allocate a buffer on the stack and fill it with a printf format string. */
#define MKSTR(name, ...) \
char name[snprintf(NULL, 0, __VA_ARGS__) + 1]; \
\
snprintf(name, sizeof(name), __VA_ARGS__)
Untested but I guess modifying that function accordingly would look like:
static inline void
rte_pmd_debug_trace(const char *func_name, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
static __thread char buffer[vsnprintf(NULL, 0, fmt, ap)];
va_end(ap);
va_start(ap, fmt);
vsnprintf(buffer, sizeof(buffer), fmt, ap);
va_end(ap);
rte_log(RTE_LOG_ERR, RTE_LOGTYPE_PMD, "%s: %s", func_name, buffer);
}
> And here's the version if we are happy to have file and line number instead of
> function name. I think this might be the best option.
>
> /Bruce
>
> #ifdef RTE_LIBRTE_ETHDEV_DEBUG
> -#define RTE_PMD_DEBUG_TRACE(fmt, args...) \
> - RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args)
> +#define RTE_PMD_DEBUG_TRACE(...) \
> + RTE_LOG(ERR, PMD, __FILE__", " RTE_STR(__LINE__) ": " __VA_ARGS__)
> #else
> -#define RTE_PMD_DEBUG_TRACE(fmt, args...)
> +#define RTE_PMD_DEBUG_TRACE(...)
> #endif
Much cleaner indeed, however __func__ might be useful when comparing log
outputs from different source code versions. I think we should keep it.
--
Adrien Mazarguil
6WIND
