CODEWITHSUNDEEP
cpointers
Kudayar Pirimbaev
Kudayar Pirimbaev

Reputation: 1320

Strange pointers initialization

Today I had an exam on ponters in C, and there was some questions about double pointers where the following syntax was used

*pointer = &variable;

I don't know if I have done correctly, but can someone explain where will pointer point to and how will the value in variable change? At first I thought it will cause sntax error, but there was no such answer in a test. Thanks in advance

Upvotes: 1

Views: 94

Answers (4)

kazinix
kazinix

Reputation: 30123

If the pointer is initialized this way:

int *pointer;
int variable = 10;

pointer = malloc(sizeof(int));
*pointer = &variable;

*pointer = &variable means the address of variable is set as value of the pointee. Since *pointer is dereferencing so you are basically storing a value not setting a reference.

Upvotes: 0

balki
balki

Reputation: 27664

pointer is a pointer to a pointer. Eg,

    int var1=42;
    int* intptr;
    int** ptr2intPtr;
    ptr2intptr = &intptr;
//Syntax in question.
    *ptr2intptr = &var1; 
//Just like *intptr is same as var1, *ptr2intptr is same as intptr
//so the above line will be equivalent to intptr = &var1
    //All the three are the same
    printf("%d",**ptr2intptr);
    printf("%d",*intptr);
    printf("%d",var1);

Upvotes: 0

codaddict
codaddict

Reputation: 455142

// two int variables.
int var1;
int var2;

// int pointer pointing to var1
int *ptr = &var1;

// pointer to int pointer..pointing to ptr
int **ptr_to_ptr = &ptr;

// now lets make the pointer pointed to by ptr_to_ptr 
// point to var2
*ptr_to_ptr = &var2;

// or alternatively you can do:
// ptr = &var2;

Upvotes: 1

ThiefMaster
ThiefMaster

Reputation: 318518

Here's an example on how you could use it:

int foo = 123;
int **bar = malloc(sizeof(int *));
*bar = &foo;

Now bar is a pointer to a pointer to foo. Doesn't make much sense though.

Upvotes: 0

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