tracepoint: Remove TRACEPOINT_LIB declaration

[lttng-ust.git] / include / ust / tracepoint.h

diff --git a/include/ust/tracepoint.h b/include/ust/tracepoint.h
index 158d9b8a4cc1d3d28fdf4546f058dc8f83868152..76645dd6a1d1fce7181022f88151aa033f508a46 100644 (file)
--- a/include/ust/tracepoint.h
+++ b/include/ust/tracepoint.h
@@ -46,26 +46,35 @@ struct tracepoint {
 #define tracepoint(name, args...)      __trace_##name(args)
 
 /*
- * Library should be made known to libust by declaring TRACEPOINT_LIB in
- * the source file. (Usually at the end of the file, in the outermost
- * scope).
+ * These weak symbols, the constructor, and destructor take care of
+ * registering only _one_ instance of the tracepoints per shared-ojbect
+ * (or for the whole main program).
+ * The dummy tracepoint entry ensures that the start/stop pointers get
+ * initialized by the linker when no tracepoints are present in a
+ * shared-object (or main program).
  */
-#define TRACEPOINT_LIB                                                 \
-       extern struct tracepoint * const __start___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
-       extern struct tracepoint * const __stop___tracepoints_ptrs[] __attribute__((weak, visibility("hidden"))); \
-       static struct tracepoint * __tracepoint_ptr_dummy               \
-       __attribute__((used, section("__tracepoints_ptrs")));           \
-       static void __attribute__((constructor)) __tracepoints__init(void) \
-       {                                                               \
-               tracepoint_register_lib(__start___tracepoints_ptrs,     \
-                                       __stop___tracepoints_ptrs -     \
-                                       __start___tracepoints_ptrs);    \
-       }                                                               \
-                                                                       \
-       static void __attribute__((destructor)) __tracepoints__destroy(void) \
-       {                                                               \
-               tracepoint_unregister_lib(__start___tracepoints_ptrs);  \
-       }
+extern struct tracepoint * const __start___tracepoints_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+extern struct tracepoint * const __stop___tracepoints_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+int __tracepoint_registered
+       __attribute__((weak, visibility("hidden")));
+
+static void __attribute__((constructor)) __tracepoints__init(void)
+{
+       if (__tracepoint_registered++)
+               return;
+       tracepoint_register_lib(__start___tracepoints_ptrs,
+                               __stop___tracepoints_ptrs -
+                               __start___tracepoints_ptrs);
+}
+
+static void __attribute__((destructor)) __tracepoints__destroy(void)
+{
+       if (--__tracepoint_registered)
+               return;
+       tracepoint_unregister_lib(__start___tracepoints_ptrs);
+}
 
 /*
  * it_func[0] is never NULL because there is at least one element in the array
@@ -182,12 +191,6 @@ int __tracepoint_probe_register(const char *name, void *probe, void *data);
 extern
 int __tracepoint_probe_unregister(const char *name, void *probe, void *data);
 
-struct tracepoint_lib {
-       struct tracepoint * const *tracepoints_start;
-       int tracepoints_count;
-       struct cds_list_head list;
-};
-
 extern
 int tracepoint_register_lib(struct tracepoint * const *tracepoints_start,
                            int tracepoints_count);