C: seg fault when filling array inside struct
I have:
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typedef struct {
int* data;
unsigned int len;
} intarr_t;
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I do:
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intarr_t* ia=malloc(sizeof(intarr_t);
ia->len =5;
int val=1;
for(int i=0; i<ia->len; i++)
{
ia->data[i]=val;
val++;
}
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I am getting a seg fault inside the for loop. What are some possible corrections? I have assert statements that pass:
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assert(ia);
assert(ia->data);
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I also tried filling the array manually which also causes a segfault:
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ia->data[0]=1;
ia->data[1]=2;
ia->data[2]=3;
ia->data[3]=4;
ia->data[4]=5;
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I just figured it out:
I need:
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ia->data=malloc(sizeof(int)*ia->len);
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I need this before filling the array.
Last edited on
The problem is that you haven't allocated space for ia->data:
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intarr_t* ia=new intarr_t; // use new/delete instead of malloc/free
ia->len =5;
ia->data = new unsigned int[5]; // allocate space for 5 items
int val=1;
for(int i=0; i<ia->len; i++)
{
ia->data[i]=val;
val++;
}
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As stated, need to assign a value to ia->data.
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intarr_t* ia = malloc(sizeof(intarr_t));
ia->len = 5;
ia->data = malloc(ia->len * sizeof (int));
int val = 1;
for (unsigned int i=0; i<ia->len; i++)
{
ia->data[i] = val;
val++;
}
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Example:
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#include <stdio.h>
#include <stdlib.h>
typedef struct {
int* data;
unsigned int len;
} intarr_t;
void display(intarr_t * intarr);
int main()
{
intarr_t one;
one.len = 5;
one.data = malloc(one.len * sizeof (int));
one.data[0] = 2;
one.data[1] = 3;
one.data[2] = 5;
one.data[3] = 7;
one.data[4] = 11;
//---------------------------
intarr_t* ia = malloc(sizeof(intarr_t));
ia->len = 5;
ia->data = malloc(ia->len * sizeof (int));
int val = 1;
for (unsigned int i=0; i<ia->len; i++)
{
ia->data[i] = val;
val++;
}
//----------------------
display(&one);
display(ia);
//--------------
free (one.data);
free (ia->data);
free (ia);
return 0;
}
void display(intarr_t * intarr)
{
printf("size = %u\n", intarr->len);
for (unsigned int i=0; i<intarr->len; ++i)
{
printf("%5u %5d\n", i, intarr->data[i]);
}
}
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size = 5
0 2
1 3
2 5
3 7
4 11
size = 5
0 1
1 2
2 3
3 4
4 5 |
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