Fix: don't generate 0-len array in tracepoint probes

It is forbidden by C99, and gcc/g++ in pedantic mode generates errors
for e.g. field-less events.

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 48085670f937d7e0c5ce2c04a08d5b18bd20e526..1e75d613350ea65c588e9928acc0093422eb25e5 100644 (file)
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -208,6 +208,7 @@ static const char                                                   \
 #define TRACEPOINT_EVENT_CLASS(_provider, _name, _args, _fields)                            \
        static const struct lttng_event_field __event_fields___##_provider##___##_name[] = { \
                _fields                                                                      \
+               ctf_integer(int, dummy, 0)      /* Dummy, C99 forbids 0-len array. */        \
        };
 
 #include TRACEPOINT_INCLUDE
@@ -618,8 +619,8 @@ void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))           \
        size_t __event_len, __event_align;                                    \
        size_t __dynamic_len_idx = 0;                                         \
        union {                                                               \
-               size_t __dynamic_len[_TP_ARRAY_SIZE(__event_fields___##_provider##___##_name)]; \
-               char __filter_stack_data[2 * sizeof(unsigned long) * _TP_ARRAY_SIZE(__event_fields___##_provider##___##_name)]; \
+               size_t __dynamic_len[_TP_ARRAY_SIZE(__event_fields___##_provider##___##_name) - 1]; \
+               char __filter_stack_data[2 * sizeof(unsigned long) * (_TP_ARRAY_SIZE(__event_fields___##_provider##___##_name) - 1)]; \
        } __stackvar;                                                         \
        int __ret;                                                            \
                                                                              \
@@ -748,7 +749,7 @@ const struct lttng_event_desc __event_desc___##_provider##_##_name = {             \
        .probe_callback = (void (*)(void)) &__event_probe__##_provider##___##_template,\
        .ctx = NULL,                                                           \
        .fields = __event_fields___##_provider##___##_template,                \
-       .nr_fields = _TP_ARRAY_SIZE(__event_fields___##_provider##___##_template), \
+       .nr_fields = _TP_ARRAY_SIZE(__event_fields___##_provider##___##_template) - 1, \
        .loglevel = &__ref_loglevel___##_provider##___##_name,                 \
        .signature = __tp_event_signature___##_provider##___##_template,       \
        .u = { .ext = { .model_emf_uri = &__ref_model_emf_uri___##_provider##___##_name } }, \
@@ -771,6 +772,7 @@ const struct lttng_event_desc __event_desc___##_provider##_##_name = {             \
 
 static const struct lttng_event_desc *_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)[] = {
 #include TRACEPOINT_INCLUDE
+       NULL,   /* Dummy, C99 forbids 0-len array. */
 };
 
 
@@ -784,7 +786,7 @@ static const struct lttng_event_desc *_TP_COMBINE_TOKENS(__event_desc___, TRACEP
 static struct lttng_probe_desc _TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER) = {
        .provider = __tp_stringify(TRACEPOINT_PROVIDER),
        .event_desc = _TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER),
-       .nr_events = _TP_ARRAY_SIZE(_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)),
+       .nr_events = _TP_ARRAY_SIZE(_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)) - 1,
        .head = { NULL, NULL },
        .lazy_init_head = { NULL, NULL },
        .lazy = 0,