From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 5 Jun 2012 17:08:54 +0000 (-0400)
Subject: Fix: perform macro expansion on tracepoint signatures
X-Git-Tag: v2.0.4~12
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=fa790c0b78e1e7441268daa8340098e418f43762;p=lttng-ust.git

Fix: perform macro expansion on tracepoint signatures

The problem can be seen by patching the demo test from lttng-ust as
follows:

--- a/tests/demo/ust_tests_demo3.h
+++ b/tests/demo/ust_tests_demo3.h
@@ -22,12 +22,14 @@ extern "C" {
  * all copies or substantial portions of the Software.
  */

+#include <stdbool.h>
+
 #include <lttng/tracepoint.h>

 TRACEPOINT_EVENT(ust_tests_demo3, done,
-       TP_ARGS(int, value),
+       TP_ARGS(bool, value),
        TP_FIELDS(
-               ctf_integer(int, value, value)
+               ctf_integer(bool, value, value)
        )
 )

Then when the demo is run with LTTNG_UST_DEBUG=1, a warning is shown,
like:

liblttng_ust_tracepoint[3315/3315]: Warning: Tracepoint signature mismatch, not
enabling one or more tracepoints. Ensure that the tracepoint probes prototypes
match the application. (in set_tracepoint() at tracepoint.c:310)
liblttng_ust_tracepoint[3315/3315]: Warning: Tracepoint "ust_tests_demo3:done"
signatures: call: "_Bool, value" vs probe: "bool, value". (in set_tracepoint()
at tracepoint.c:312)

It seems that TP_ARGS does not perform preprocessor expansion on the
"bool" type spec, while something underneath TP_FIELDS does. And since
(at least on this Centos 6.2 box) stdbool.h uses a #define rather than a
typedef to make bool equivalent to _Bool, liblttng detects a mismatch.

Reported-by: John Steele Scott <toojays@toojays.net>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index 520f8c06..c2e95192 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -444,15 +444,19 @@ static void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))\
 #include <lttng/ust-tracepoint-event-reset.h>
 
 #undef TP_ARGS
-#define TP_ARGS(args...) #args
+#define TP_ARGS(args...) args
+
+#define _TP_EXTRACT_STRING2(...)	#__VA_ARGS__
 
 #undef TRACEPOINT_EVENT_CLASS
 #define TRACEPOINT_EVENT_CLASS(_provider, _name, _args, _fields)	\
 const char __tp_event_signature___##_provider##___##_name[] = 		\
-		_args;
+		_TP_EXTRACT_STRING2(_args);
 
 #include TRACEPOINT_INCLUDE
 
+#undef _TP_EXTRACT_STRING2
+
 /*
  * Stage 6 of tracepoint event generation.
  *