Allocated memory - Struct with array already alloc

Question

I've got the following example :

#define MAX_SIZE 32 

typedef struct T {
     int total_data;
     D *data;
} T;

typedef struct D {
     int type;
     char value[MAX_SIZE];  
} D;

I've got a part which extract and fill D* data; And one who print it.

The part which extract and fill D extract data from a file.

void extract(T *_t) {
     // Open file
     fscanf(fp, "%d\n", &_t->total_data);
     _t->data = malloc(_t->total_data * sizeof(*_t->data);

     // Extract and fill 
     for ( i = 0; i < _t->total_data; i++) 
         fscanf(fp, "%d:%[^$]\n", &(_t->data[i].type), _t->data[i].value);
 }

The function which read looks like this :

void read(T *_t) {
    int i; 
    for( i = 0; i < _t->total_data; i++) 
         printf("%d - %s", _t->data[i].type, _t->data[i].value);
}

But I've got a crash .. I don't know why .. the code looks ok for me according to what I've found on the web. Could you please help me ?

Thanks.

Files look like that :

2
0:ABC
1:DEFGHI

For exemple

I have only looked at the code so far... always make sure malloc hasn't returned NULL. Especially given the fact you're reading from a file, you could run out of memory. Always assume you might run out of memory anyway :) — a-d
– a-d, Commented Oct 14, 2019 at 23:09
Possible duplicate of Freeing array of structs inside struct — kaldoran
– kaldoran, Commented Oct 15, 2019 at 7:44

4386427 · Accepted Answer · 2019-10-14 18:50:49Z

1

This line:

fscanf(fp, "%d\n", _t->total_data);

is invalid. _t->total_data is an int but you need a pointer to int in order to scan data.

Try

fscanf(fp, "%d\n", &_t->total_data);
                   ^
                   note

BTW: Didn't your compile give a warning for this ?

answered Oct 14, 2019 at 18:50

4386427

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2 Comments

kaldoran Over a year ago

Well .. nope he did not >< I'll take a look ! Thanks

a-d Over a year ago

@kaldoran do you use the flags -Wall -Wextra with your compiler? Works with gcc g++ and clang (maybe others compilers too)

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