Is bool data type supported in embedded C?

Question

The wrote the following code for avr MCU and I compiled and uploaded the code with Arduino IDE, I did not get any error and the code works but I remembered C program does not support bool data type. Will this code still be compiled with avr-gcc on Linux.

//The following code is written for ATmega328P microcontroller
// Turns ON the led on a click of a switch and Turns OFF it again another click
#include <avr/io.h>
#include <avr/interrupt.h>


#define LED_PIN   PB5
#define SW_PIN    PD2


volatile bool ledOn = false;


// Function to initialize pinmode and interrupt
void init() {
 // Set LED pin as output
  DDRB = DDRB |(1 << DDB5);
  // Set switch pin as  pull-up resistor
  PORTD = PORTD |(1 << SW_PIN);
  // Enable interrupt on the switch pin
  EIMSK = EIMSK |(1 << INT0);
  // Trigger interrupt on failing edge of the switch signal
  EICRA = (1 << ISC01);
  // Enable global interrupts
  sei();
}


// Interrupt service routine for the switch
ISR(INT0_vect) {
  // If the switch is pressed, toggle the LED state
  if ((~PIND & (1 << SW_PIN)) && !ledOn) {
   PORTB = PORTB | (1 << LED_PIN);
    ledOn = true;
  }
  else{
  PORTB = PORTB & ~(1 << LED_PIN);
    ledOn = false;
  }

}

int main(void) {
 // Initialization
  init();

 // Loop forever
 while (1) {

    // NOP
  }

  return 0;
}```

Answer 1

The Arduino IDE uses C++ compilation - you are using C++ not C - even if it is otherwise valid C code, and you are not using the Arduino setup()/loop() framework or Arduino libraries..

With respect to C however, C99 defines a built-in type _Bool. It does that because of all the pre-C99 code that exists that might define types or macro aliases for Boolean in various ways. It prevents breaking existing code that the introduction of a new keywords bool, true and false might otherwise cause.

C99 also defines a header stdbool.h which provides a C++-like bool alias for _Bool, and symbols for true and false values. Including stdbool.h or cstdbool in C++ code has no effect.

The Arduino compiler is the same AVR GCC cross-compiler you are proposing to use on linux. It supports both C and C++ compilation. You can use the avr-g++ driver for C++ compilation, but its only difference to the avr-gcc driver is that it links C++ library support implicitly when invoking ld. Otherwise C or C++ compilation is determined by command line switch or by source file extension.

So your code will compile as-is with AVR GCC if you use the same C++ compilation that Arduino applies, but if you want to ensure it builds with either C or C++ compilation (or you just want to make it valid C code) you can simply add #include <stdbool.h> and it will work in either case.