struct

// -std=c99 -Wall -Wextra -Wpedantic -Wshadow

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define TEST_STR_MAX 512

struct st {
    char str1[TEST_STR_MAX];
    char str2[TEST_STR_MAX];
    char *str3;
    int iv;
    double dv;
};

int main()
{

    struct st st_arr[100];

    char teststr[] = "Test";

    st_arr[0] = ( struct st ){ "One", "Two", NULL, 1, 0.1 };
    st_arr[1] = ( struct st ){ "Ice", "Cream", NULL, 123, 2.1 };
    st_arr[2] = ( struct st ){ 0 };

    // with designated initializers

    st_arr[3] = ( struct st ){ .str1 = "Penguin", .str2 = "Antarctica" };
    st_arr[4] = ( struct st ){ .str2 = "Antarctica", .str1 = "Penguin", .dv = 321.1 };
    st_arr[5] = ( struct st ){ .str1 = "Again", .iv = 5 };
    st_arr[6] = ( struct st ){ .str2 = "String" };
    st_arr[7] = ( struct st ){ .str3 = teststr };
    st_arr[8] = ( struct st ){ .iv = 32 };

    for ( int i = 0; i < 9; ++i )
    {
        printf( "(%d) %s %s %s %d %f\n",
            i,
            strlen( st_arr[i].str1 ) ? st_arr[i].str1 : "ZeroLen",
            strlen( st_arr[i].str2 ) ? st_arr[i].str2 : "ZeroLen",
            st_arr[i].str3 ? st_arr[i].str3 : "NULL",
            st_arr[i].iv,
            st_arr[i].dv
        );

        printf ("    *st_arr[%d].str1: %s *st_arr[%d].str2: %s\n",
                i,
                *st_arr[i].str1 ? "NonZero" : "Zero",
                i,
                *st_arr[i].str2 ? "NonZero" : "Zero"
        );

        printf( "    %p %p %p\n",
                (void*) st_arr[i].str1,
                (void*) st_arr[i].str2,
                (void*) st_arr[i].str3
        );

    }

    return 0;
}

/*
output:

(0) One Two NULL 1 0.100000
    *st_arr[0].str1: NonZero *st_arr[0].str2: NonZero
    0x7ffca60c7120 0x7ffca60c7320 (nil)
(1) Ice Cream NULL 123 2.100000
    *st_arr[1].str1: NonZero *st_arr[1].str2: NonZero
    0x7ffca60c7538 0x7ffca60c7738 (nil)
(2) ZeroLen ZeroLen NULL 0 0.000000
    *st_arr[2].str1: Zero *st_arr[2].str2: Zero
    0x7ffca60c7950 0x7ffca60c7b50 (nil)
(3) Penguin Antarctica NULL 0 0.000000
    *st_arr[3].str1: NonZero *st_arr[3].str2: NonZero
    0x7ffca60c7d68 0x7ffca60c7f68 (nil)
(4) Penguin Antarctica NULL 0 321.100000
    *st_arr[4].str1: NonZero *st_arr[4].str2: NonZero
    0x7ffca60c8180 0x7ffca60c8380 (nil)
(5) Again ZeroLen NULL 5 0.000000
    *st_arr[5].str1: NonZero *st_arr[5].str2: Zero
    0x7ffca60c8598 0x7ffca60c8798 (nil)
(6) ZeroLen String NULL 0 0.000000
    *st_arr[6].str1: Zero *st_arr[6].str2: NonZero
    0x7ffca60c89b0 0x7ffca60c8bb0 (nil)
(7) ZeroLen ZeroLen Test 0 0.000000
    *st_arr[7].str1: Zero *st_arr[7].str2: Zero
    0x7ffca60c8dc8 0x7ffca60c8fc8 0x7ffca60e0a83
(8) ZeroLen ZeroLen NULL 32 0.000000
    *st_arr[8].str1: Zero *st_arr[8].str2: Zero
    0x7ffca60c91e0 0x7ffca60c93e0 (nil)

*/