ESP32 load GPIOs via header files - esp32

Question

I have a big school project with an ESP32. Almost all GPIOs are used in the project, so I want to have the whole thing a bit cleaner.
If I declare all GPIOs in the main then it doesn't look so nice. Therefore I created a header file where all GPIOs are declared.
Here is an example:
//setPinConfig.h
const int start = 13;
const int stop = 9;
void setPinConfig()
{
pinMode(start, INPUT);
pinMode(stop, INPUT);
}
Then I call this function in the setup of the Main function.
//main.cpp
#include "setPinConfig.h"
void setup()
{
setPinConfig();
}
In the main, everything works the way I want it to. But if I now want to access the GPIOs in other header files, it comes to errors.
I work around this by using "#ifndef", #define, #endif in the header files in which I call the GPIO header file.
I am now wondering if this is a legitimate way to deklare and load the GPIOs. Or should I rather declare and load it classically in the main.

Answer 1

In short, you can't define functions in the header files (technically you can, but then you're in a world of pain). You define them in the .c or .cpp file, and declare in the .h file.
If you wish to create a new module (pair of .h and .c files) for configuring GPIO pins, it would look something like so:
Sample setPinConfig.h file:
#ifndef _SET_PIN_CONFIG
#define _SET_PIN_CONFIG
const int start = 13;
const int stop = 9;
// This function sets the GPIO pins' configuration
void setPinConfig();
#endif // _SET_PIN_CONFIG
Then sample setPinConfig.c
#include "setPinConfig.h"
void setPinConfig()
{
pinMode(start, INPUT);
pinMode(stop, INPUT);
}