----- On May 19, 2021, at 12:56 PM, lttng-dev lttng-dev@lists.lttng.org wrote:
> Try to use vsnprintf with a 512 Byte buffer on the Stack,
> if that fails allocate a larger one.
I agree with the approach.
Can we move the hardcoded "512" to a #define within src/common/tracer.h ?
Thanks,
Mathieu
>
> Signed-off-by: Norbert Lange <nolang...@gmail.com>
> ---
> liblttng-ust/tracef.c | 13 ++++++++++---
> liblttng-ust/tracelog.c | 12 +++++++++---
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/liblttng-ust/tracef.c b/liblttng-ust/tracef.c
> index ea98e43e..18c29e25 100644
> --- a/liblttng-ust/tracef.c
> +++ b/liblttng-ust/tracef.c
> @@ -32,17 +32,24 @@
> void _lttng_ust_tracef(const char *fmt, ...)
> {
> va_list ap;
> - char *msg;
> + char local_buf[512];
> + char *msg = local_buf;
> int len;
>
> va_start(ap, fmt);
> - len = vasprintf(&msg, fmt, ap);
> + len = vsnprintf(local_buf, sizeof(local_buf), fmt, ap);
> + if (len >= sizeof(local_buf)) {
> + msg = (char *)malloc(len + 1);
> + len = msg ? vsnprintf(msg, len + 1, fmt, ap) : -1;
> + }
> +
> /* 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:
> + if (msg != local_buf)
> + free(msg);
> va_end(ap);
> }
> diff --git a/liblttng-ust/tracelog.c b/liblttng-ust/tracelog.c
> index 65fc87ed..a5d110fa 100644
> --- a/liblttng-ust/tracelog.c
> +++ b/liblttng-ust/tracelog.c
> @@ -35,19 +35,25 @@
> const char *fmt, ...) \
> { \
> va_list ap; \
> - char *msg; \
> + char local_buf[512]; \
> + char *msg = local_buf; \
> int len; \
> \
> va_start(ap, fmt); \
> - len = vasprintf(&msg, fmt, ap); \
> + len = vsnprintf(local_buf, sizeof(local_buf), fmt, ap); \
> + if (len >= sizeof(local_buf)) { \
> + msg = (char *)malloc(len + 1); \
> + len = msg ? vsnprintf(msg, len + 1, fmt, ap) : -1; \
> + } \
> /* len does not include the final \0 */ \
> if (len < 0) \
> goto end; \
> __tracepoint_cb_lttng_ust_tracelog___##level(file, \
> line, func, msg, len, \
> LTTNG_UST_CALLER_IP()); \
> - free(msg); \
> end: \
> + if (msg != local_buf) \
> + free(msg); \
> va_end(ap); \
> }
>
> --
> 2.30.2
>
> _______________________________________________
> 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
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