Fix: liblttng-ctl: ABI-breaking size change of lttng_session struct

[lttng-tools.git] / include / lttng / session.h

diff --git a/include/lttng/session.h b/include/lttng/session.h
index 6c54d7e4f5e55fc5fe4dde03ff8a4812e5411a97..7e328b625f29ffcef9faf6fbcdc1172a83f45805 100644 (file)
--- a/include/lttng/session.h
+++ b/include/lttng/session.h
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2014 - David Goulet <dgoulet@efficios.com>
 /*
  * Copyright (C) 2014 - David Goulet <dgoulet@efficios.com>

+ * Copyright (C) 2019 - Jérémie Galarneau <jeremie.galarneau@efficios.com>

  *
  * This library is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License, version 2.1 only,
  *
  * This library is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License, version 2.1 only,


@@ -23,6 +24,7 @@ extern "C" {
 #endif
 
 struct lttng_session_descriptor;
 #endif
 
 struct lttng_session_descriptor;

+struct lttng_destruction_handle;

 
 /*
  * Basic session information.
 
 /*
  * Basic session information.


@@ -32,7 +34,7 @@ struct lttng_session_descriptor;
  *
  * The structures should be initialized to zero before use.
  */
  *
  * The structures should be initialized to zero before use.
  */

-#define LTTNG_SESSION_PADDING1             12
+#define LTTNG_SESSION_PADDING1             8

 struct lttng_session {
        char name[LTTNG_NAME_MAX];
        /*
 struct lttng_session {
        char name[LTTNG_NAME_MAX];
        /*


@@ -49,7 +51,29 @@ struct lttng_session {
        uint32_t snapshot_mode;
        unsigned int live_timer_interval;       /* usec */
 
        uint32_t snapshot_mode;
        unsigned int live_timer_interval;       /* usec */
 

+       /*
+        * End of public attributes.
+        * The remaining fields are used to deal with ABI management concerns.
+        */
+
+       /*
+        * 32-bit architectures are already naturally aligned on 4 bytes after
+        * 'live_timer_interval'. However, the offset does not result in a
+        * natural alignment on 64-bit architectures. Adding 4 bytes of
+        * padding here results in an aligned offset after 'alignement_padding'
+        * for both bitnesses.
+        *
+        * This was added since not all compilers appear to align unions in the
+        * same way. Some (e.g. MSVC) do not seem to impose an alignement
+        * constraint while others (e.g. gcc, clang, icc) seem to align it to
+        * ensure 'ptr' is naturally aligned.
+        */
+       char alignment_padding[4];

        union {
        union {

+               /*
+                * Ensure the 'extended' union has the same size for both
+                * 32-bit and 64-bit builds.
+                */

                char padding[LTTNG_SESSION_PADDING1];
                void *ptr;
        } extended;
                char padding[LTTNG_SESSION_PADDING1];
                void *ptr;
        } extended;


@@ -132,6 +156,21 @@ extern int lttng_create_session_live(const char *name, const char *url,
  */
 extern int lttng_destroy_session(const char *name);
 
  */
 extern int lttng_destroy_session(const char *name);
 

+/*
+ * Destroy a tracing session.
+ *
+ * Performs the same function as lttng_destroy_session(), but provides
+ * an lttng_destruction_handle which can be used to wait for the completion
+ * of the session's destruction. The lttng_destroy_handle can also be used
+ * obtain the status and archive location of any implicit session
+ * rotation that may have occured during the session's destruction.
+ *
+ * Returns LTTNG_OK on success. The returned handle is owned by the caller
+ * and must be free'd using lttng_destruction_handle_destroy().
+ */
+extern enum lttng_error_code lttng_destroy_session_ext(const char *session_name,
+               struct lttng_destruction_handle **handle);
+

 /*
  * Behaves exactly like lttng_destroy_session but does not wait for data
  * availability.
 /*
  * Behaves exactly like lttng_destroy_session but does not wait for data
  * availability.