Re: [PATCH v3 lttng-ust 1/2] Introduce vtracef

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

----- On Feb 26, 2020, at 4:14 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> ----- On Feb 24, 2020, at 12:34 PM, Maxime Roussin-Belanger
> maxime.roussinbelanger@gmail.com wrote:
> [...]
>> diff --git a/liblttng-ust/tracef.c b/liblttng-ust/tracef.c
>> index ea98e43e..1311f0d5 100644
>> --- a/liblttng-ust/tracef.c
>> +++ b/liblttng-ust/tracef.c
>> @@ -29,20 +29,26 @@
>> #define TRACEPOINT_DEFINE
>> #include "lttng-ust-tracef-provider.h"
>> 
>> -void _lttng_ust_tracef(const char *fmt, ...)
>> +void _lttng_ust_vtracef(const char *fmt, va_list ap)
>> {
>> -	va_list ap;
>> 	char *msg;
>> -	int len;
>> -
>> -	va_start(ap, fmt);
>> -	len = vasprintf(&msg, fmt, ap);
>> +	const int len = vasprintf(&msg, fmt, ap);
>> 	/* len does not include the final \0 */
>> 	if (len < 0)
>> 		goto end;
>> 	__tracepoint_cb_lttng_ust_tracef___event(msg, len,
>> 		LTTNG_UST_CALLER_IP());
> 
> I don't think LTTNG_UST_CALLER_IP() has the behavior we would expect
> for _lttng_ust_tracef() anymore here. We want the callsite in the application
> or library which has been instrumented, not an IP within lttng-ust.

The following should fix both inlining and CALLER_IP() issues:

static inline __attribute__((always_inline))
void __lttng_ust_vtracef(const char *fmt, va_list ap)
{
        char *msg;
        const int len = vasprintf(&msg, fmt, ap);
        /* len does not include the final \0 */
        if (len < 0)
                goto end;
        __tracepoint_cb_lttng_ust_tracef___event(msg, len,
                LTTNG_UST_CALLER_IP());
        free(msg);
end:
        return;
}

void _lttng_ust_vtracef(const char *fmt, va_list ap)
{
        __lttng_ust_vtracef(fmt, ap);
}

void _lttng_ust_tracef(const char *fmt, ...)
{
        va_list ap;

        va_start(ap, fmt);
        __lttng_ust_vtracef(fmt, ap);

        va_end(ap);
}

Thanks,

Mathieu


> 
> Thanks,
> 
> Mathieu
> 
>> 	free(msg);
>> end:
>> +	return;
>> +}
>> +
>> +void _lttng_ust_tracef(const char *fmt, ...)
>> +{
>> +	va_list ap;
>> +
>> +	va_start(ap, fmt);
>> +	_lttng_ust_vtracef(fmt, ap);
>> +
>> 	va_end(ap);
>> }
>> --
>> 2.20.1
>> 
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev@lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com