stdbool.h (along with float.h, limits.h, stdarg.h, stddef.h, stdint.h, and some other library facilities) is required to be provided even in freestanding environment so, at least as long as you use an ISO C conformant compiler, you can always include those even if you don’t have a libc implementation

Make sure there’s only one strong reference and call Arc::into_inner to move it out of the Arc. Same can be done with Mutex::into_inner to move the transaction out of the mutex