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GS
www.ElectricRCAircraftGuy.com
24 Sept. 2020
Learn how to pass sized arrays as parameters (via references) in C++!
References:
1. https://stackoverflow.com/questions/1328223/when-a-function-has-a-specific-size-array-parameter-why-is-it-replaced-with-a-p/1328246#1328246
1. https://stackoverflow.com/questions/1328223/when-a-function-has-a-specific-size-array-parameter-why-is-it-replaced-with-a-p/1328242#1328242
*******************************************************************************/
#include <cstdint>
#include <cstdio>
void foo(uint8_t array[100])
{
// is ALWAYS sizeof(uint8_t*), which is 8!
printf("sizeof(array) = %lu\n", sizeof(array));
}
void foo2(uint8_t (&array)[100])
{
printf("sizeof(array) = %lu\n", sizeof(array));
}
template<size_t N>
void foo3(uint8_t (&array)[N])
{
printf("sizeof(array) = %lu\n", sizeof(array));
}
int main()
{
printf("Hello World\n");
printf("\n");
uint8_t a1[10];
uint8_t a2[11];
uint8_t a3[12];
// Is `sizeof(array) = 8` for all of these!
foo(a1);
foo(a2);
foo(a3);
printf("\n");
// Fails to compile for these 3! Sample error:
// > main.cpp:49:12: error: invalid initialization of reference of type ‘uint8_t (&)[100]
// > {aka unsigned char (&)[100]}’ from expression of type ‘uint8_t [10] {aka unsigned char [10]}’
// > foo2(a1);
// > ^
// foo2(a1);
// foo2(a2);
// foo2(a3);
// ------------------
// Works just fine for this one since the array `a4` has the right length!
// Is `sizeof(array) = 100`
uint8_t a4[100];
foo2(a4);
printf("\n");
foo3(a1);
foo3(a2);
foo3(a3);
foo3(a4);
printf("\n");
return 0;
}
/*
SAMPLE OUTPUT:
Hello World
sizeof(array) = 8
sizeof(array) = 8
sizeof(array) = 8
sizeof(array) = 100
sizeof(array) = 10
sizeof(array) = 11
sizeof(array) = 12
sizeof(array) = 100
*/