'Is this a safe / correct implementation of a variadic list argument used to simplify setting "pinMode"?

Code (C++):

I'm new to C++ so I'm not sure if this is safe:

#include <Arduino.h>

void pin_mode(uint8_t pins[], uint8_t mode) {
  const int length = *(&pins + 1) - pins;
  for (size_t i = 0; (signed)i < length; i++) {
    pinMode(pins[i], mode);
  }
}

I have multiple pins that have the same pin setting, I'd like to set their values on one line instead of having 12 + lines that call the same function.

Usage:

pin_mode([PIN_1, PIN_2, PIN_3, PIN_4], OUTPUT);

Is this a safe / correct implementation?

c++arduino


Solution 1:[1]

If I were doing this, I'd pass the array by reference, so the compiler would compute its size for me:

#include <Arduino.h>

template <size_t N>
void pin_mode(uint8_t (&pins)[N], uint8_t mode) {
  for (size_t i = 0; i < N; i++) {
    pinMode(pins[i], mode);
  }
}

Of course, with this you're free to use a range-based for loop if you prefer.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Jerry Coffin

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