X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=include%2Flttng%2Fsession.h;h=7e328b625f29ffcef9faf6fbcdc1172a83f45805;hp=8ba8179136f09931ed66e21247fa3124d69e408f;hb=e9af56b3027eebc314384a797c01e6a7e35c8fd2;hpb=3e3665b89947ebdd812bcfaca1090d22b34d5778 diff --git a/include/lttng/session.h b/include/lttng/session.h index 8ba817913..7e328b625 100644 --- a/include/lttng/session.h +++ b/include/lttng/session.h @@ -34,7 +34,7 @@ struct lttng_destruction_handle; * * 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]; /* @@ -51,7 +51,29 @@ struct lttng_session { 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 { + /* + * Ensure the 'extended' union has the same size for both + * 32-bit and 64-bit builds. + */ char padding[LTTNG_SESSION_PADDING1]; void *ptr; } extended; @@ -130,7 +152,7 @@ extern int lttng_create_session_live(const char *name, const char *url, * * The name can't be NULL here. * - * Returns LTTNG_OK on success, else a negative LTTng error code. + * Return 0 on success else a negative LTTng error code. */ extern int lttng_destroy_session(const char *name);