Error taking address of temporary array when passing compound literal array

Question

I have an Arduino sketch that passes an array into a method as a compound literal, but for some reason I keep getting the following error:

void setup() { }
void printConcatLine(char chunks[][20]) { }
void loop() { 
 printConcatLine((char[][20]){ "{", "255", "}" });
}

I've also tried passing the number of the pointers/length of the array, and explicitly terminating it:

void setup() { }
void printConcatLine(char *chunks[]) { }
void loop() { 
 printConcatLine((char*[]){ "{", "255", "}", NULL });
}

...and

void setup() { }
void printConcatLine(char chunks[][20]) { }
void loop() { 
 printConcatLine((char[][20]){ "{", "255", "}", "" });
}

But they both produce the same error.

What is the correct method of passing the compound literal array as a method parameter?

• Majenko: You can't. You have to assign it to something then pass that variable.
• Majenko: Either that or rewrite your function to use variadic arguments.
• VerySeriousSoftwareEndeavours: Is this limitation specific to Arduino? From what I understand you can do this in C.
• Majenko: I am not sure, but I suspect it's a consequence of the AVR being a Modified Harvard Architecture CPU.
• Majenko: stackoverflow.com/questions/32941846/…

Answer 1

You can't with the Arduino. I am not quite sure why, but I think it may be because it's a Modified Harvard architecture machine.

You can better achieve what you want with variadic arguments, however:

void printConcatLine(int num, ...) {
 va_list ap;
 const char *s;
 va_start(ap, num);
 for (int i = 0; i < num; i++) {
 s = va_arg(ap, const char *);
 Serial.print(s);
 }
 va_end(ap);
 Serial.println();
}
void setup() {
 Serial.begin(115200);
 printConcatLine(3, "{", "255", "}");
}
void loop() {
}

The first argument is the number of arguments that follow, and all the rest are string constants.