Assigning int array to a int pointer

Question

I want to assign value of an array to a pointer or need a better way to do the below operation .

I have a structure

struct ver{
    int *a;
    int *b
    int *c;
}

struct Versions{
    int ver1[3];
    int ver2[3];
    int ver3[9];
}

static const Versions versionsinfo[] {
    "001234",
    {0,18,0},
    "000000"
};

static Temp_Data;

Versions * GetVersions() {
    Versions * pt = NULL;
    memcpy(&Temp_Data,&versionsinfo[1]);
    pt = &Temp_Data;
    return pt ;
}

struct Versions *pointer;
pointer = GetVersions();    

struct ver *newVer;
newVer->a= pointer->ver1;
newVer->b= pointer->ver2;
newVer->c= pointer->ver3;

I want to assign the value of Ver1 to a member of struct ver , either a, b or c.

can anyone please let me know if this is possible in C.

Its just `newVer->a = Ver1; newVer->b = Ver2; newVer->c = Ver3;`. What is the issue ? — Prajval M, Dec 17 '18 at 16:35
You need to allocate some memory for `struct ver *newVer;` before you can copy to its members. — Weather Vane, Dec 17 '18 at 16:36
"... want to assign the value of Ver1 ..." --> Arrays can not be _assigned_. Code like `newVer->a=Ver1` will assign the address of `Ver1[0]` to the pointer `newVer->a`. pranathi, Describe your overall goal in more detail. — chux - Reinstate Monica, Dec 17 '18 at 16:37
What are you _actually_ trying to do? This smells somewhat like an [XY Problem](http://xyproblem.info) — Jabberwocky, Dec 17 '18 at 16:37
I get segmentation fault if I do this and my device keeps resetting . — pranathi, Dec 17 '18 at 16:39
I have updated the question . So if I execute this code on the device , my device is resetting continuously — pranathi, Dec 17 '18 at 16:43
pranathi, Hint, what is the value of `newVer` in the line `newVer->a= Ver1;`? The prior line `struct ver *newVer;` does not initialize `newVer` to anything. — chux - Reinstate Monica, Dec 17 '18 at 16:46
Perhaps you could change the type of `newVer` to `struct ver` (instead of `struct ver *`) unless you specifically need `newVer` to be a pointer. Then set the members using `newVer.a = pointer->ver1;`, `newVer.b = pointer->ver2;`, `newVer.c = pointer->ver3;`. — Ian Abbott, Dec 17 '18 at 16:51
Your code looks very wrong. Lots of `;` missing, wrong syntax, etc. Please post a [MCVE]. It's so wrong that it's really hard to guess what your intention is. — Jabberwocky, Dec 17 '18 at 16:55
Thanks @lan Abbott!. That solved my reset problem , but still I cannot get the correct values assigned from `newVer.b = pointer->ver2` — pranathi, Dec 17 '18 at 17:11

PerfectContrast · Answer 1 · 2018-12-17T19:24:28.200

1

Well,

int Ver1[3];
int Ver2[9];
int Ver3[9];

They are initializing arrays of type int. So if you want to get those numbers (which are the sizes of the arrays in the above) you need to do

int Ver1 = 3;
int Ver2 = 9;
int Ver3 = 9;

The allocate some memory for the pointer

struct ver *newVer = malloc(sizeof(newVer));

and then put the values in the struct

newVer[0].a = Ver1;
newVer[0].b = Ver2;
newVer[0].c = Ver3;

edited Dec 17 '18 at 19:24

answered Dec 17 '18 at 16:46

PerfectContrast

144
2
2
14

`sizeof(newVer)` --> `sizeof *newVer`. `malloc(sizeof(newVer))` allocates the size of the pointer, not the structure. – chux - Reinstate Monica Dec 17 '18 at 16:47
Or `newVer[0].a = &Ver1` if your compiler won't convert. – tadman Dec 17 '18 at 16:47
Thanks for the response tadman!! but I just want to assign member of struct Versions. Could you please take a look at my updated question . – pranathi Dec 17 '18 at 16:55
@PerfectContrast Do you mean `newVer[0].a = &Ver1;` and so on ? – Prajval M Dec 17 '18 at 17:01
@Prajval Nope . I want the whole content in `ver1[3] in int*a` – pranathi Dec 17 '18 at 17:05
`malloc(sizeof(newVer));` remains incorrect code as the allocation is too small. – chux - Reinstate Monica Dec 17 '18 at 22:12

H.cohen · Answer 2 · 2018-12-17T16:50:31.517

1

Hope this helps

struct ver
{
  int *a;
  int *b;
  int *c;
};

int Ver1[3] = {1,2,3};
int Ver2[3] = {1,2,3};;
int Ver3[9];

struct ver *newVer;

int main()
{
   struct ver newV;/*the memory for struct var is allocated in main */

   newVer = (struct ver *)malloc(sizeof(struct ver));/*memory allocated in heap*/

   newV.a = Ver1;/*OR newVar.a = &Ver1[0];*/
   newV.b = Ver2;
   newV.c = Ver3;
   printf("newV->a[0] is %d", newV.a[0]);
  /*OR*/
  newVer->a = Ver1;
  newVer->b = Ver2;
  newVer->c = Ver3;
  printf("\nnewVar->a[1] is %d", newVer->a[1]);
  free(newVer); 

  return 0;
}

edited Dec 17 '18 at 16:50

answered Dec 17 '18 at 16:47

H.cohen

517
3
9

Curious, why do you code `(struct ver *)`? Why not drop it? – chux - Reinstate Monica Dec 17 '18 at 16:49
malloc returns (void*) which works just fine, but it's good practice to specify (struct ver *) – H.cohen Dec 17 '18 at 16:52
2

The cast if s OK, but about 80% suggest not to cast: [Do I cast the result of malloc?](https://stackoverflow.com/q/605845/2410359). Consider `newVer = malloc(sizeof *newVer);` It is easy to code right, review and maintain. – chux - Reinstate Monica Dec 17 '18 at 16:55

Assigning int array to a int pointer

2 Answers2