[Due] pgm_read_ptr causes error

[arduino]

[Due] pgm_read_ptr causes error

[PaulStoffregen]

On Mega2560, the following sketch compiles OK:

It may compile, but it certainly doesn't work. It has 3 fatal flaws:

1: There's no Serial.begin(), so it can't print anything
2: It doesn't actually store any pointers for pgm_read_ptr() to read. The array has 5 chars (including terminating zero), not a pointer to chars.
3: The array is local scope (stack allocated), which doesn't work with PROGMEM.

Here is a correct program which actually works when run on Uno or Mega (yes, I did just test both of them).

const char * const str_debug_1[] PROGMEM = {"ECHO", "ECHO2"};

void setup() {
  Serial.begin(9600);
  Serial.println("test pgm_read_ptr:");
  Serial.println((char*)pgm_read_ptr(&str_debug_1[0]));
  Serial.println((char*)pgm_read_ptr(&str_debug_1[1]));
}

void loop() {
}

This doesn't solve the issue on Arduino Due, but at least a working test case might be helpful?

[bobc]

There is no doubt that pgm_read_ptr works on AVR platforms, so it doesn't help at all, frankly. Creating a runnable test case for Due once the compile issue has been fixed is a trivial exercise.

Any thoughts on how to fix it?

[PaulStoffregen]

Use (*(void * const *)(addr))

arduino/ArduinoCore-samd@4ffc9d2