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Out of curiosity what version of c++ are the R4 using?

C++17, see here.

Consequently constexpr should not be a problem.

Mind updating the PR accordingly?, i.e. constexpr uint8_t D0 = PIN_D0;.

@aentinger - done. Faster turn time than yesterday. But if I try to compile this example on the minima:

void setup() {
  Serial.begin(115200);
  while(!Serial && millis() < 5000) {}
  int D0 = 1;
  Serial.println(D0);
  //digitalWrite(D0, HIGH);
}

void loop() {}

I will get this error using constexpr:

C:\Users\Merli\AppData\Local\Arduino15\packages\arduino\hardware\renesas_uno\1.0.2\variants\MINIMA/pins_arduino.h:75:8: error: unknown type name 'constexpr'
 static constexpr uint8_t D0 = PIN_D0;
        ^~~~~~~~~
C:\Users\Merli\AppData\Local\Arduino15\packages\arduino\hardware\renesas_uno\1.0.2\variants\MINIMA/pins_arduino.h:75:26: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'D0'
 static constexpr uint8_t D0 = PIN_D0;

Well, I get a lot of errors, but none like you ... 🤔

/home/alex/Arduino/hardware/arduino-git/renesas/variants/UNOWIFIR4/pins_arduino.h:54:31: error: 'PIN_D0' was not declared in this scope
 static constexpr uint8_t D0 = PIN_D0;
                               ^~~~~~
/home/alex/Arduino/hardware/arduino-git/renesas/variants/UNOWIFIR4/pins_arduino.h:54:31: note: suggested alternative: 'PIN_A0'
 static constexpr uint8_t D0 = PIN_D0;
                               ^~~~~~
                               PIN_A0
/home/alex/Arduino/hardware/arduino-git/renesas/variants/UNOWIFIR4/pins_arduino.h:55:31: error: 'PIN_D1' was not declared in this scope
 static constexpr uint8_t D1 = PIN_D1;
                               ^~~~~~

oops - darn copy and paste error. Just pushed the fix to clear up the errors you are seeing.

I suppose you'll also need to extend support for Portenta C33?

Ok - updated.

It seems the problem is that Arduino.h and by extension pins_arduino.h produce an error when included into a C file, i.e. cortex_handlers.c in this case.

Try renaming cortex_handlers.c to .cpp and prefix Stacktrace_Handler with extern "C":

-void Stacktrace_Handler(void) {
+extern "C" void Stacktrace_Handler(void) {

I've reconsidered, drop constexpr and let's go with const as you've proposed since it will provide broader compatibility.

@aentinger
Revert back to const . And Welcome back.

Merged, thank you!