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 715c5d56836d7172879bf209cc069c9db2e51f57..a470e8cdebb6d626f70814584523986400406ab1 100644 (file)
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -169,6 +169,7 @@ static const char                                                   \
 #define TRACEPOINT_ENUM(_provider, _name, _values)                     \
        const struct lttng_enum_entry __enum_values__##_provider##_##_name[] = { \
                _values                                                 \
+               ctf_enum_value("", 0)   /* Dummy, 0-len array forbidden by C99. */ \
        };
 
 #include TRACEPOINT_INCLUDE
@@ -288,6 +289,7 @@ 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. */        \
        };
 
 #undef TRACEPOINT_ENUM
@@ -295,7 +297,7 @@ static const char                                                   \
        static const struct lttng_enum_desc __enum_##_provider##_##_name = {            \
                .name = #_provider "_" #_name,                                          \
                .entries = __enum_values__##_provider##_##_name,                        \
-               .nr_entries = _TP_ARRAY_SIZE(__enum_values__##_provider##_##_name),     \
+               .nr_entries = _TP_ARRAY_SIZE(__enum_values__##_provider##_##_name) - 1, \
        };
 
 #include TRACEPOINT_INCLUDE
@@ -729,8 +731,8 @@ 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;                                                            \
                                                                              \
@@ -863,7 +865,7 @@ static 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 = {                                                                 \
@@ -890,6 +892,7 @@ static 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. */
 };
 
 
@@ -903,7 +906,7 @@ 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,