Enforce the device-serial length

[psi-4ward]

AS we know, the device-serial must be exactly 10 chars.

I've accidentally used only 9 chars which results in substantial problems after paring:

• The CCU allows to pair but the device does not show up in devices-list
• The CCU produces huge amount of errors in the logs
• Node-RED (redmatic and the fork from @ptweety) crashes because of invalid-chars in device-name when unmarshalling the response XML

Should we enforce the serial-length by code? Ideally on compile-time but I did not find a working solution.

[pa-pa]

Would be good. But I have no idea how to do that at compile time.

[stan23]

Something like:

#define ASSERT_IF_NOT_EQUAL(a, b)   char compile_time_assert[((a) == (b)) ? 1 : -1];

ASSERT_IF_NOT_EQUAL (sizeof(serial)/sizeof(char), 11);

The trick is to create an array of negative size.
Untested as I’m typing on the phone.

Edit: must be 11 due to termination character.

[stan23]

If you name the array serial_is_not_10_characters it gets pretty obvious in the compiler error message.

[TomMajor]

das funktioniert in der IDE mit der ich gerade arbeite (ist aber nicht Arduino) :

#define SERIAL "1234567890"
_Static_assert((sizeof(SERIAL) - 1) == 10, "SERIAL length must be 10 characters!");
-> alles Bestens

bei SERIAL "123456789" oder SERIAL "1234567890a" :
-> [C++ Error] static_assert failed "SERIAL length must be 10 characters!"

-1 da hier der Null-Terminator mitgezählt wird im Gegensatz zu strlen().