Printing array struct of struct

Question

I have an array struct that is inside another struct, but I don't know how to print the value of the son struct in a function.

The main struct is something like:

 struct person{
    char name[10];
    int cash;
    listMov mov[];
};
typedef person Person;
Person user[50];

And the son struct

struct listaMovimenti{
    int bonifico;
    char beneficiario[10];
};
typedef struct listaMovimenti listMov;

listMov mov[2] = {{150, "Ponzi" },
                   {2000, "Gotti"}};

I've tried with something like this but with no success.

printf("Name %s and %d",user[0].mov[1].beneficiario, user[0].mov[1].bonifico);

Define "no success". Did the code fail to compile? Did it crash? etc...etc... — Chris Turner
– Chris Turner, Commented Feb 19, 2018 at 16:59
And also include in your question the code that shows how you're populating user too — Chris Turner
– Chris Turner, Commented Feb 19, 2018 at 17:01
This is called flexible member array and it doesn't work that way. You must use dynamic allocation if you want to use that. — iBug
– iBug, Commented Feb 19, 2018 at 17:05
@ChrisTurner, beneficiario's string prints blank, the int bonifico prints 0. I populate user name and cash through a simply scanf. — rulezzer
– rulezzer, Commented Feb 19, 2018 at 17:07
But how do you populate user mov? It's different to the mov variable you've included code for — Chris Turner
– Chris Turner, Commented Feb 19, 2018 at 17:08

4386427 · Accepted Answer · 2018-02-19 18:29:51Z

First:

The variable listMov mov[2] has no relation to the listMov mov[]; inside the struct. They have the same name but the scope is different. They are simply completely unrelated.

Second:

listMov mov[];

means you have a flexible array inside the struct. When you use a flexible array in a struct, you have to use dynamic memory allocation to reserve the amount of memory that you need. Using Person user[50]; is kind of meaningless as no memory is reserved for the flexible arrays.

Use of flexible arrays is a bit difficult. In most cases it is easier just to use a pointer like:

struct person{
    char name[10];
    int cash;
    listMov* mov;
};
typedef person Person;
Person user[50];

and then allocate memory like

user[0].mov = malloc(N * sizeof(listMov)); // N is thee number of elements needed

Then you can do:

user[0].mov[0].bonifico = 150;
strcpy(user[0].mov[0].beneficiario, "Ponzi");
user[0].mov[1].bonifico = 200;
strcpy(user[0].mov[1].beneficiario, "Gotti");

printf("Name %s and %d",user[0].mov[1].beneficiario, user[0].mov[1].bonifico);

Remember that you need a new malloc for every user[i] that you use.

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