Answer by Lundin for Simple state machine

Implementing state machines with a table with function pointers is very common. The table should however be read-only and preferably stored in flash. This does however seem to be some PC-like ARM with Linux?

The design with a centralized state transition decision-maker is particularly important and your program is well-written there. Picking next state, based on the result from the previous, should be done at one single place in the program, not in each individual state ("stateghetti programming"). With a centralized decision-maker, you can also easily implement a safe mode for the program where it goes upon certain critical errors.

Regarding the state machine/array:

• typedef enum state_transitions - the enum tag state_transitions is useless and can be removed.
• At the end of sbState enum, include a member for size such as sbStates or what you wish to call it. Then change the states[9] to states[] and static_assert(sizeof states/sizeof *states == sbStates, "states data inconsistent"); to guarantee data integrity.
• Assuming char name[255]; will never change, then 255 bytes per array item is wasteful. A char* to a string literal will save loads of read-only memory over this.
• states should be const.

So you could instead have something like:

static const sbStateDef states[] = {    [sbIdle] =        {"Idle", sbIdleState,           {{sbStartupTrans, sbStartup}, {sbSelfTestTrans, sbSelfTest}}},    [sbSelfTest] =    {"Self Test", sbSelfTestState,  {{sbStartupTrans, sbStartup}, {sbErr, sbIdle}}},    ...};static_assert(sizeof states/sizeof *states == sbStates, "states data inconsistent"); // C11

You can do similar with transitions. Overall, designated array initializers like above, that make use of the enum is strongly recommended for readability and data integrity.

General comments:

• Never define variables in header files, ever. If you ever find yourself with the need to define a variable in a header, something has gone fundamentally wrong in your program design. In this case you could probably put both the allocation of the state machine and the calling code in main.c.
• All the while(1) loops mean that you can't change states... I'm assuming this is just place-holders? Such loops are unacceptable in a hosted multi-process system such as Linux. You should probably consider porting this to pthreads and put the thread to sleep when it isn't working.