Infinite loop when using size_t in a count down for loop

Question

So I\'m using size_t instead of int in any indexing for loop to prevent negative indices. But when counting down, this leads to an overflow:

<

Answer 1

A simplest way is to increase the upper value. For example

const size_t N = 10;

for (size_t i = N + 1; i != 0; --i) {
    // Do something, f.ex. array[i-1] = i-1
}

or

const size_t N = 10;

for (size_t i = N + 1; i-- != 0; ) {
    // Do something, f.ex. array[i] = i
}

In general case when i can be equal to the maximum value stored in an object of the type size_t you can use the following trick

#include 

int main( void )
{
    const size_t N = 10;

    for (size_t i = N, j = N; !( i == 0 && j == -1 ); j--)
    {
        i = j;
        printf( "%zu ", i );
    }

    printf( "\n" );
}

Otherwise you can use do-while loop. It is more suitable in this case. For example

size_t i = N;

do
{
    printf( "%zu ", i );
} while ( i-- != 0 );