ESP8266 Community Forum

Posted: **Thu May 05, 2016 3:59 pm**

I need to pass different strings to a function. When I do so I get the compiler warning: "deprecated conversion from string constant to 'char*'".

The sketch loads to the ESP8266 and works just fine. If I run the same sketch on the Arduino Uno, I don't even get the warning.

Here is a very simple code example that produces the warning (actually twice):

Code: Select all

void functionToPassTo(char* someString){
  //some code
}
void setup() {
  functionToPassTo("Hello");
  functionToPassTo("GoodBy");

}

It seems the proper way to do this is as follows:

Code: Select all

void functionToPassTo(char* someString){
  //some code
}

void setup() {
  char passToFunction_1[] = "Hello";
  functionToPassTo(passToFunction_1);

  char passToFunction_2[] = "GoodBy";
  functionToPassTo(passToFunction_2);
}

That's a lot more code. If I use the "proper method" I would have to create about 30 variables to handle all my function calls.

Is there any hidden danger of using the code that produces the compiler warnings?

Thanks and regards

Posted: **Thu May 05, 2016 4:56 pm**

No, there is no danger at all.
But if you wish to unpollute the log, and since your function will never try to overwrite those strings, simply change your function as follow :

Code: Select all

void functionToPassTo(const char* someString){
  //some code
}

ESP8266 Community Forum

deprecated conversion from string constant to 'char*

deprecated conversion from string constant to 'char*

Re: deprecated conversion from string constant to 'char*