Re: [PATCH v2] tools/lib/traceevent: Replace str_error_r() with an open coded implementation

From: Jiri Olsa
Date: Mon Sep 24 2018 - 14:07:22 EST


On Fri, Sep 21, 2018 at 03:20:37PM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
>
> While working on having PowerTop use libtracevent as a shared object
> library, Tzvetomir hit "str_error_r not defined". This was added by commit
> c3cec9e68f12d ("tools lib traceevent: Use str_error_r()") because
> strerror_r() has two definitions, where one is GNU specific, and the other
> is XSI complient. The strerror_r() is in a wrapper str_error_r() to keep the
> code from having to worry about which compiler is being used.
>
> The problem is that str_error_r() is external to libtraceevent, and not part
> of the library. If it is used as a shared object then the tools using it
> will need to define that function. I do not want that function defined in
> libtraceevent itself, as it is out of scope for that library.
>
> As there's only a single instance of this call, I replaced it with an open
> coded algorithm that just uses strerror() and strncpy() to place the error
> message in the given buffer. We don't need to worry about the errors that
> strerror_r() returns. If the buffer isn't big enough, we simply truncate it.
>
> Reported-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

> ---
>
> Changes from v1:
>
> - Account for buflen being zero (do nothing).
>
> tools/lib/traceevent/event-parse.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index 7980fc6c3bac..ba7570646d2c 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -18,7 +18,6 @@
> #include <errno.h>
> #include <stdint.h>
> #include <limits.h>
> -#include <linux/string.h>
> #include <linux/time64.h>
>
> #include <netinet/in.h>
> @@ -6215,7 +6214,12 @@ int tep_strerror(struct tep_handle *pevent __maybe_unused,
> const char *msg;
>
> if (errnum >= 0) {
> - str_error_r(errnum, buf, buflen);
> + const char *error_str = strerror(errnum);
> +
> + if (buflen > 0) {
> + strncpy(buf, error_str, buflen);
> + buf[buflen - 1] = 0;
> + }
> return 0;
> }
>
> --
> 2.13.6
>