Example:
void foo (char * s)
{
Serial.println (s);
}
void setup ()
{
Serial.begin (115200);
Serial.println ();
foo ("bar");
} // end of setup
void loop ()
{
} // end of loop
Warning:
sketch_jul14b.ino: In function ‘void setup()’:
sketch_jul14b.ino:10: warning: deprecated conversion from string constant to ‘char*’
The function foo expects a char* (which it can therefore modify) but you are passing a string literal, which should not be modified.
The compiler is warning you not to do this. Being deprecated it might turn from a warning into an error in a future compiler version.
Solution: Make foo take a const char *:
void foo (const char * s)
{
Serial.println (s);
}