From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 18 Oct 2016 21:56:42 +0000 (-0400)
Subject: Fix: loglevel and model_emf_uri with g++ compiled probes
X-Git-Tag: v2.10.0-rc1~38
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=4ea4f80e8c57628907b035bd1a0372f7b8faec51

Fix: loglevel and model_emf_uri with g++ compiled probes

Fix the loglevel and model_emf_uri features for probe providers compiled
with g++. They were previously effectless because of C++ symbol name
mangling. The weakref was refering to the non-mangled symbol, but C++
emits a mangled symbol for the static variable.

Fix this by emitting an extern "C" symbol with hidden visibility on C++.
With a C compiled, this simply turns a static variable into a variable
with hidden visibility.

Fixes: #1069

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 0b4e5a26..2bb4a38e 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -844,14 +844,31 @@ static const char __tp_event_signature___##_provider##___##_name[] = 	\
 /* Reset all macros within TRACEPOINT_EVENT */
 #include <lttng/ust-tracepoint-event-reset.h>
 
+/*
+ * Declare _loglevel___##__provider##___##__name as non-static, with
+ * hidden visibility for c++ handling of weakref. We do a weakref to the
+ * symbol in a later stage, which requires that the symbol is not
+ * mangled.
+ */
+#ifdef __cplusplus
+#define LTTNG_TP_EXTERN_C extern "C"
+#else
+#define LTTNG_TP_EXTERN_C
+#endif
+
 #undef TRACEPOINT_LOGLEVEL
 #define TRACEPOINT_LOGLEVEL(__provider, __name, __loglevel)		   \
 static const int _loglevel_value___##__provider##___##__name = __loglevel; \
-static const int *_loglevel___##__provider##___##__name =		   \
+LTTNG_TP_EXTERN_C const int *_loglevel___##__provider##___##__name	   \
+		__attribute__((visibility("hidden"))) =			   \
 		&_loglevel_value___##__provider##___##__name;
 
 #include TRACEPOINT_INCLUDE
 
+#ifdef __cplusplus
+#undef LTTNG_TP_EXTERN_C
+#endif
+
 /*
  * Stage 6.1 of tracepoint event generation.
  *
@@ -861,12 +878,29 @@ static const int *_loglevel___##__provider##___##__name =		   \
 /* Reset all macros within TRACEPOINT_EVENT */
 #include <lttng/ust-tracepoint-event-reset.h>
 
+/*
+ * Declare _model_emf_uri___##__provider##___##__name as non-static,
+ * with hidden visibility for c++ handling of weakref. We do a weakref
+ * to the symbol in a later stage, which requires that the symbol is not
+ * mangled.
+ */
+#ifdef __cplusplus
+#define LTTNG_TP_EXTERN_C extern "C"
+#else
+#define LTTNG_TP_EXTERN_C
+#endif
+
 #undef TRACEPOINT_MODEL_EMF_URI
 #define TRACEPOINT_MODEL_EMF_URI(__provider, __name, __uri)		   \
-static const char *_model_emf_uri___##__provider##___##__name = __uri;
+LTTNG_TP_EXTERN_C const char *_model_emf_uri___##__provider##___##__name   \
+		__attribute__((visibility("hidden"))) = __uri		   \
 
 #include TRACEPOINT_INCLUDE
 
+#ifdef __cplusplus
+#undef LTTNG_TP_EXTERN_C
+#endif
+
 /*
  * Stage 7.1 of tracepoint event generation.
  *