[PATCH 3/6] tools/lib/traceevent: Changed return logic of trace_seq_printf() and trace_seq_vprintf() APIs

From: Steven Rostedt
Date: Fri Nov 30 2018 - 23:08:58 EST


From: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
tools/lib/traceevent/trace-seq.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/lib/traceevent/trace-seq.c b/tools/lib/traceevent/trace-seq.c
index 8ff1d55954d1..8d5ecd2bf877 100644
--- a/tools/lib/traceevent/trace-seq.c
+++ b/tools/lib/traceevent/trace-seq.c
@@ -100,7 +100,8 @@ 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
@@ -129,9 +130,10 @@ 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;
}

/**
@@ -139,6 +141,10 @@ 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
@@ -163,9 +169,10 @@ 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;
}

/**
--
2.19.1