@@ -30,8 +30,9 @@ list of arguments _args_ in the trace sequence _s_.
RETURN VALUE
------------
-Both _trace_seq_printf()_ and _trace_seq_vprintf()_ functions return non-zero
-on success, or 0 in case of an error.
+Both _trace_seq_printf()_ and _trace_seq_vprintf()_ functions return 0 if the
+trace oversizes the buffer's free space, the number of characters printed, or
+a negative value in case of an error.
EXAMPLE
-------
@@ -43,7 +44,7 @@ EXAMPLE
struct trace_seq seq;
trace_seq_init(&seq);
...
-if (trace_seq_printf(&seq, "example print %d", 10) == 0) {
+if (trace_seq_printf(&seq, "example print %d", 10) <= 0) {
/* Failed to print in the trace sequence */
}
...
@@ -51,7 +52,7 @@ void my_print(char *format, ...)
{
va_list ap;
va_start(ap, format);
- if (trace_seq_printf(&seq, format, ap) == 0) {
+ if (trace_seq_printf(&seq, format, ap) <= 0) {
/* Failed to print in the trace sequence */
}
va_end(ap);
@@ -114,7 +114,8 @@ static void expand_buffer(struct trace_seq *s)
* @fmt: printf format string
*
* It returns 0 if the trace oversizes the buffer's free
- * space, 1 otherwise.
+ * space, the number of characters printed, or a negative
+ * value in case of an error.
*
* The tracer may use either sequence operations or its own
* copy to user routines. To simplify formating of a trace
@@ -143,9 +144,10 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
goto try_again;
}
- s->len += ret;
+ if (ret > 0)
+ s->len += ret;
- return 1;
+ return ret;
}
/**
@@ -153,6 +155,10 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
* @s: trace sequence descriptor
* @fmt: printf format string
*
+ * It returns 0 if the trace oversizes the buffer's free
+ * space, the number of characters printed, or a negative
+ * value in case of an error.
+ * *
* The tracer may use either sequence operations or its own
* copy to user routines. To simplify formating of a trace
* trace_seq_printf is used to store strings into a special
@@ -177,9 +183,10 @@ trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
goto try_again;
}
- s->len += ret;
+ if (ret > 0)
+ s->len += ret;
- return len;
+ return ret;
}
/**
In order to make libtraceevent into a proper library, its API should be straightforward. The trace_seq_printf() and trace_seq_vprintf() APIs have inconsistent returned values with the other trace_seq_* APIs. This path changes the return logic of trace_seq_printf() and trace_seq_vprintf() - to return the number of printed characters, as the other trace_seq_* related APIs. Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com> --- .../Documentation/libtraceevent-tseq_print.txt | 9 +++++---- tools/lib/traceevent/trace-seq.c | 17 ++++++++++++----- 2 files changed, 17 insertions(+), 9 deletions(-)