`debug.h` undefines ENABLE_DEBUG`, use:
```c
#define ENABLE_DEBUG (1)
#if ENABLE_DEBUG
#   define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_PRINTF
#   define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_PRINTF
#else
#   define PTHREAD_REAPER_STACKSIZE KERNEL_CONF_STACKSIZE_IDLE
#   define PTHREAD_STACKSIZE KERNEL_CONF_STACKSIZE_DEFAULT
#endif
#include "debug.h"
```