Deprecated Conversion error

Question

I am writing a code for ARDUINO UNO in arduino 1.8.1 and the following error is coming How to remove it?

C:\Users\Mahe\Documents\Arduino\sketch_mar09b\sketch_mar09b.ino: In function 'void updateState(byte)':

C:\Users\Mahe\Documents\Arduino\sketch_mar09b\sketch_mar09b.ino:243:60: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]

 DisplayInfo("RFID Scanner", "Starting up", HIGH, HIGH);

Answer 1

I am writing a code for ARDUINO UNO in arduino 1.8.1 and the following error is coming How to remove it?

C:\Users\Mahe\Documents\Arduino\sketch_mar09b\sketch_mar09b.ino:243:60: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
 DisplayInfo("RFID Scanner", "Starting up", HIGH, HIGH);

To give a detailed answer the full prototype for DisplayInfo() is needed. The issue is that the literal strings are const char* and the function parameters are declared as char*.

The correct way to fix this would be to update DisplayInfo() so that the parameter types are const char*. The dirty fix is to cast the parameters in the call.

 DisplayInfo((char*) "RFID Scanner", (char*) "Starting up", HIGH, HIGH);

But I would not recommend that.

Cheers!

• caligari: The correct way is always the better and the header of DisplayInfo() should be changed to use const keyword in parameters. If code is third party, author/maintainer should be also informed to patch it. Good answer @mikael-patel :)
• Code Gorilla: An alternative is to declare some string constants and then pass the variable names into the function. i.e. const char cRFIDScanner[] = "RFID Scanner"; const char cStarting[] = "Starting up"; DisplayInfo(cRFIDScanner, cStarting, HIGH, HIGH);