How to free char array in struct

Question

I see that you can free char * pointers within struct but how do you free char[N] inside a struct

typedef struct Edge
{
    char number[13];
    int numOfCalls;
    struct Edge *next;
} Edge;

When I do this i get an error

Edge *edge = malloc(sizeof(Edge));
edge->next = NULL;
strcpy(edge->number,numberOne);  // numberOne is also a char[13];
free(edge->number);
free(edge);

You don't have to, you use free with ponters pointing to a (m/re/c)alloced area. Here number is not a pointer. — David Ranieri
– David Ranieri, Commented Nov 7, 2021 at 6:40

Guseul Heo · Accepted Answer · 2021-11-07 07:14:33Z

1

If you use char array (char number[13]) in struct, you don't have to malloc or free the array. Once you do malloc for struct Edge, there is also space for number in memory.

In summary, if you use char pointer as a member of struct Edge, you need to malloc or free memory space for char pointer, but you don't have to do that in your case. Therefore, delete free(edge->number) line.

answered Nov 7, 2021 at 7:14

Guseul Heo

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Chris · Accepted Answer · 2021-11-07 06:43:19Z

0

The lifespan of number in the struct Edge is automatic. Even if you dynamically allocate an Edge struct, when you free the struct, you'll free the memory for the char array.

answered Nov 7, 2021 at 6:43

Chris

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2 Comments

Eric Postpischil Over a year ago

The lifetime of the structure whose memory was reserved with malloc is allocated, not automatic, and so too is the lifetime of any member within it.

Chris Over a year ago

Indeed. However, I was sitting of the char array within the struct.

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