Fix auto_init_recursive_mutex definition for C++ (#875)

Co-authored-by: Graham Sanderson <graham.sanderson@gmail.com>

Author: earlephilhower

src/common/pico_sync/include/pico/mutex.h

@@ -289,7 +289,7 @@ static inline bool recursive_mutex_is_initialized(recursive_mutex_t *mtx) {
  *
  * But the initialization of the mutex is performed automatically during runtime initialization
  */
-#define auto_init_recursive_mutex(name) static __attribute__((section(".mutex_array"))) recursive_mutex_t name = { .core.spin_lock = (spin_lock_t *)1 /* marker for runtime_init */ }
+#define auto_init_recursive_mutex(name) static __attribute__((section(".mutex_array"))) recursive_mutex_t name = { .core = { .spin_lock = (spin_lock_t *)1 /* marker for runtime_init */ }, .owner = 0, .enter_count = 0 }
 
 #ifdef __cplusplus
 }

test/kitchen_sink/kitchen_sink.c

@@ -110,6 +110,9 @@ __force_inline int something_inlined(int x) {
     return x * 2;
 }
 
+auto_init_mutex(mutex);
+auto_init_recursive_mutex(recursive_mutex);
+
 int main(void) {
     spiggle();
 
@@ -118,6 +121,12 @@ int main(void) {
     printf("HI %d\n", something_inlined((int)time_us_32()));
     puts("Hello Everything!");
     puts("Hello Everything2!");
+
+    hard_assert(mutex_try_enter(&mutex, NULL));
+    hard_assert(!mutex_try_enter(&mutex, NULL));
+    hard_assert(recursive_mutex_try_enter(&recursive_mutex, NULL));
+    hard_assert(recursive_mutex_try_enter(&recursive_mutex, NULL));
     // this should compile as we are Cortex M0+
     __asm volatile("SVC #3");
+
 }