Create Declaration / Definition in current file

Discussed in https://github.com/microsoft/vscode-cpptools/discussions/10642

^{Originally posted by FernandoGarcia March 7, 2023}
Hi!

I would to know how to create function prototype in an Arduino code while using Platformio.

I'm talking about this type of code:

main.cpp

#include <Arduino.h>
#include <Bounce2.h>

#define NUM_RELAYS 3
#define INITIAL_STATE LOW  // Initial state = HIGH to active LOW relay model.

struct INFOS
{
  const byte relayPin;
  bool relayState;
  const byte buttonPin;
};

INFOS info[NUM_RELAYS] =
{
  {2, INITIAL_STATE, 18}, // Relay 0 pin, relay 0 state, button 0 pin
  {4, INITIAL_STATE, 19},
  {5, INITIAL_STATE, 21}
};

Bounce2::Button button[NUM_RELAYS] = {Bounce2::Button()};

void setup()
{
  Serial.begin(9600);

  for (byte i = 0; i < NUM_RELAYS; i++)
  {
    button[i].attach(info[i].buttonPin, INPUT_PULLUP);
    button[i].setPressedState(LOW);
    button[i].interval(5);

    pinMode(info[i].relayPin, OUTPUT);
    digitalWrite(info[i].relayPin, info[i].relayState);
  }
}

void loop()
{
  for (byte i = 0; i < NUM_RELAYS; i++)
  {
    button[i].update();

    if (button[i].pressed())
    {
      info[i].relayState = !info[i].relayState;
      digitalWrite(info[i].relayPin, info[i].relayState);
      printDebug(i);
      break;
    }
  }
}

void printDebug(byte i)
{
  Serial.print("Button ");
  Serial.print(i);
  Serial.print(" pressed, relayState ");
  Serial.print(i);
  Serial.print(": ");
  Serial.println(info[i].relayState);
}

The compiling error for this code is:

src/main.cpp: In function 'void loop()':
src/main.cpp:47:7: error: 'printDebug' was not declared in this scope
       printDebug(i);
       ^~~~~~~~~~
src/main.cpp:47:7: note: suggested alternative: 'Printable'
       printDebug(i);
       ^~~~~~~~~~
       Printable
*** [.pio/build/uno/src/main.cpp.o] Error 1

So I have always to create manually all functions prototypes on top of my code in this way:

void printDebug(byte i);

I have tried the new feature of C++ extension but it doesn't works well for this type of code.

The declaration is being placed in Arduino.h header file what is not correct for this case.

Thanks in advance.

Best regards.

Reproduce the issue using the provided main.cpp example in a PlatformIO Arduino project, focusing on the Create Definitions and Declarations feature. Compare the generated declaration placement with Arduino.h and the current file context. Done means the function prototype is placed in the current source file rather than Arduino.h.