Thread: strange problem, not sure what is wrong

This is code that is giving me trouble:

Code:

int main(void) {
const	char Off[] = "Off";
	Sensor *X = new Sensor("On", "near the front door");
	MainFrame *W = new MainFrame("Off");
	
	cout << "Sensor X is located " << X->GetLocation() << endl;
	cout << "Sensor X is currently " << X->GetSensorState() << endl;

The output from this code should be:
Sensor X is located near the front door (this works)
Sensor X is currently On

Instead I get:
Sensor X is located near the front door
Sensor X is currently Onnear the front door

This is the function GetSensorState:

Code:

inline	char *GetSensorState()  { return State; }

All it does is return State which is a protected character array. State is defined as
char State[2] (only meant to hold 'On' or 'Off' so i figured 2 is enough)

The function GetLocation is:

Code:

 inline	char *GetLocation()  { return itsLocation; }

All GetLocation does is return itsLocation which is a protected character array that describes the location of the sensor
itsLocation is defined as:
char itsLocation[50];

I am honestly not sure what is wrong here, this is quite strange.

Character arrays are terminated by '\0'. "off" is three characters, plus the terminating null character, so you need [4] in your char array.

char State[2] holds two char's, not two C-strings, i.e. "on"/"off". There's no provision for the terminating '\0' character in either case.

The compiler reads data from an array until the '\0' char is found and terminates the read. Even a full array must end with '\0'.

Note that the compiler will both "overwrite" and "overread" your array boundaries. Not a good thing since you can corrupt memory contiguous to your array if the former occurs and read absolute garbage in the case of the latter.

Initializing 'State' to [4] allocates space for the '\0' char provided nothing longer than "off" is written to the array.

-Skipper

re-read my problem please
it only doesn't work in one part of my program, but works in another part.
I don't know if the character array is causing my problem (I don't think it is)

plus i am going to try rewriting the same program using strings

I agree I think the problem is your getssensorstate string, It can only hold 1 letter and a null terminating character that is how it knows the stribng has come to an end, if you just up this to 4 then it will allow you to hold 'o' 'n' '\0' and 'o' 'f' 'f' '\0', if the function is trying to return a string that is too short then I think it could cause trouble.