Deprecated conversion from string constant to 'char*' [-Wwrite-strings] error in Arduino sketch

Question

I'm sending sensor data using Arduino and ESP8266. But while compiling the sketch in Arduino I'm getting an error saying - deprecated conversion from string constant to 'char*' [-Wwrite-strings].

#include "SoftwareSerial.h"
SoftwareSerial esp(10, 11);// RX, TX
void setup() {
  esp.begin(9600);
  Serial.begin(9600);
  delay(100);
  Serial.println("Started...");
  reset();
  connectWifi();
}

//reset the esp8266 module
void reset() {
  esp.println("AT+RST");
  delay(1000);
  if (esp.find("OK")) Serial.println("Module Reset"); //error
}

There are two "string constants" on that line, please put the body of the `if` statement on a separate line and it will be easier to know which of the two the compiler means. — Some programmer dude, Apr 05 '16 at 08:45
Also, what is `esp`? What is `esp.find()`? Not knowing Arduino programming that well, is it a standard object? Something you declared yourself? — Some programmer dude, Apr 05 '16 at 08:46
esp os softwareserial / predefined object. i did not declared esp. — STACK2, Apr 05 '16 at 08:52
where is two string constants . im not getting two string constants. can u edit it @JoachimPileborg — STACK2, Apr 05 '16 at 08:54
By "string constant" I assume the compiler means the string literals, and on the offending line you have `"OK"` and `"Module Reset"`. — Some programmer dude, Apr 05 '16 at 08:56
According to [this `SoftwareSerial` reference](https://www.arduino.cc/en/Reference/SoftwareSerial) there is no `find` member function? — Some programmer dude, Apr 05 '16 at 09:00
just add a cast (char *) before your string. Not the best way, but it works, and in arduino it's not so bad. — Aeldred, Apr 05 '16 at 09:01
then how to check check if value is ok or not ? in esp.. im new in iot and esp8266. how to cast can u plz edit that line .@Aeldred — STACK2, Apr 05 '16 at 09:02

score 2 · Answer 1 · answered Apr 30 '16 at 11:55

As Aeldred said you have just to cast you String to char*.

so your sketch will looks like :

#include "SoftwareSerial.h"
SoftwareSerial esp(10, 11);// RX, TX
void setup() {
  esp.begin(9600);
  Serial.begin(9600);
  delay(100);
  Serial.println("Started...");
  reset();
  connectWifi();
}

//reset the esp8266 module
void reset() {
  esp.println("AT+RST");
  delay(1000);
  if (esp.find((char*)"OK")) Serial.println("Module Reset"); //error
}

Deprecated conversion from string constant to 'char*' [-Wwrite-strings] error in Arduino sketch

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