Multiple definitions of variable

Projects Programming
1

I am running into an error whenever I try to upload to my ESP32, I get:

consts.h:12: multiple definition of `mqtt_server'; .pio\build\esp32dev\src\connections.cpp.o:C:\Users\<user>\Documents\PlatformIO\Projects\TelTestCheck/src/consts.h:12: first defined here

consts.h

//wifi login 
#pragma once

#define WIFI_NETWORK "Home network"
#define WIFI_PASSWORD "DA552567"

#define WIFI_TIMEOUT_MS 20000

const double stepRotation = 3200.0;


const char* mqtt_server = "127.0.0.1";
const int mqttPort = 1883;

timeUtills.h

#ifndef timeUtils_h
#define timeUtils_h

#include <NTPClient.h>
#include <Arduino.h>
#include "connections.h"

const long  gmtOffset_sec = 3600*5;
const int   daylightOffset_sec = 3600;
const char* ntpServer = "pool.ntp.org";

Connections conn;

class ntpUtils{

    public:  
        void ntpStart();
        void timeKeep();
        void timeIncrement();

};


#endif

connections.h

#ifndef connections_H
#define connections_H 

#include <Arduino.h>
#include <WiFi.h>
#include <WiFiUdp.h>
#include <PubSubClient.h>
#include <ArduinoJson.h>
#include "consts.h"

void callback(char* topic, byte* payload, unsigned int length);
class Connections{
    String epfemValues[73][4];
    void connectToWiFi();
    void mqttConnect();
    void loopCon();
};

#endif

I have narrowed the problem down to a file called timeUtils.h which contains an include to connections.h, if this include is removed the problem goes away but I do need the connections class. Im not sure how to fix this error

Thanks

2

you have defined an identifier in a number of files
in header files when you declare an identifier which is defined elsewhere in the progrma use extern
e.g. in const.h

extern const char* mqtt_server;
extern const int mqttPort ;

otherwise the the compiler allocates storage for the variables multiple times and the linker displays multiple definition error messages

3

As a rule, you shouldn't put the definitions in the .h files, use the .c or .cpp instead

4

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