How to access nested structure using pointer and array?

Question

typedef struct
{
    unsigned int a;
    unsigned char b[10];
    unsigned char c;
}acc1;

typedef struct
{
    unsigned char z[10];
    acc1 *x,y[10];
}acc2;

extern acc2 p[2];

I want to access struct acc1 variables from acc2 array p[2].

I'm getting segmenatation faults when I do it. Please guide on how to do this

"segmenatation fault problem is coming many times" -- Please show your code. — Spikatrix
– Spikatrix, Commented Jun 27, 2015 at 8:38
Note that x is a pointer to acc1 while y is an array of 10 acc1, not an array of pointers. Maybe it is what you want, maybe not. These cases are better written in separated lines: acc1 *x; acc1 y[10];. — rodrigo
– rodrigo, Commented Jun 27, 2015 at 8:52
strcpy(p[0].x->b,"1024"); getting segmantation fault on this what to do ?? — kabhis
– kabhis, Commented Jun 30, 2015 at 4:59

alk · Accepted Answer · 2015-06-27 09:18:51Z

2

To access y's elements do:

char c = p[some index between 0 and 1].y[some index between 0 and 9].c

To access elements referred to by x do:

size_t i = some index between 0 and 1;
p[i].x = malloc(somenumber_of_elements * sizeof *p[i].x);
if (NULL == p[i].x)
{
  abort(); /* Failure to allocate memory. */
}
char c = p[i].x[some index less then somenumber_of_elements].c;

Referring kabhis comment

p[0].x->c is it not correct ?

Assuming the allocation above with somenumber_of_elements greater 0, then:

char c = p[i].x[0].c;

is equivalent to

char c = p[i].x->c;

and for somenumber_of_elements greater 1

char c = p[i].x[1].c;

is equivalent to

char c = (p[i].x + 1)->c;

and so on ...

edited Jun 27, 2015 at 9:18

answered Jun 27, 2015 at 8:45

alk

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3 Comments

alk Over a year ago

@kabhis: How did p[0].x got initialised? Also this might be worth another question.

kabhis Over a year ago

typedef struct { unsigned char addr[20]; }access1; typedef struct { acess1 *st }access2; access2 arr[8] , *abb[10]; abb[i]=arr; then how can i access addr[20] printf("%s",abb[i]->st->addr);///// how to print these values.

alk Over a year ago

I do not see how this is related to the question. You might want to pose another question for this.

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