Fix static provider linking: introduce TRACEPOINT_PROBE_DYNAMIC_LINKAGE

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

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index fa39b272d8ff19527fd065c7e393ac947b46c8b2..887c9deea87b4653d944f8b9658b454d380de8bb 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -152,18 +152,35 @@ extern int __tracepoint_probe_unregister(const char *name, void *func, void *dat
 
 #ifdef TRACEPOINT_DEFINE
 
+/*
+ * When TRACEPOINT_PROBE_DYNAMIC_LINKAGE is defined, we do not emit a
+ * unresolved symbol that requires the provider to be linked in. When
+ * TRACEPOINT_PROBE_DYNAMIC_LINKAGE is not defined, we emit an
+ * unresolved symbol that depends on having the provider linked in,
+ * otherwise the linker complains. This deals with use of static
+ * libraries, ensuring that the linker does not remove the provider
+ * object from the executable.
+ */
+#ifdef TRACEPOINT_PROBE_DYNAMIC_LINKAGE
+#define _TRACEPOINT_UNDEFINED_REF(provider)
+#else  /* TRACEPOINT_PROBE_DYNAMIC_LINKAGE */
+#define _TRACEPOINT_UNDEFINED_REF(provider)    \
+       &__tracepoint_provider_##provider,
+#endif /* TRACEPOINT_PROBE_DYNAMIC_LINKAGE */
+
 /*
  * Note: to allow PIC code, we need to allow the linker to update the pointers
  * in the __tracepoints_ptrs section.
  * Therefore, this section is _not_ const (read-only).
  */
 #define _DEFINE_TRACEPOINT(provider, name)                                     \
+       extern int __tracepoint_provider_##provider;                            \
        static const char __tp_strtab_##provider##___##name[]                   \
                __attribute__((section("__tracepoints_strings"))) =             \
                        #provider ":" #name;                                    \
        struct tracepoint __tracepoint_##provider##___##name                    \
                __attribute__((section("__tracepoints"))) =                     \
-                       { __tp_strtab_##provider##___##name, 0, NULL };         \
+                       { __tp_strtab_##provider##___##name, 0, NULL, _TRACEPOINT_UNDEFINED_REF(provider) };            \
        static struct tracepoint * __tracepoint_ptr_##provider##___##name       \
                __attribute__((used, section("__tracepoints_ptrs"))) =          \
                        &__tracepoint_##provider##___##name;