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Pointer assignment in C?

+3 votes
154 views

See the following two statement

float *ptr = malloc( sizeof(*ptr) );

and 

float *ptr;
ptr = malloc( sizeof(*ptr) );

In first case we allocate the memory to *ptr and in the second to ptr, why is such a difference.

posted Nov 6, 2014 by anonymous

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2 Answers

+1 vote
 
Best answer

In term of final result both are same.

First one is pointer is got initialized (assigned an initial value) at the time of declaration.

Second one is declaration then separately initialized to the memory location given by malloc().

So,

float  *ptr = malloc(sizeof(*ptr));  is nothing but
float *ptr  (declaration)  and  (ptr = malloc(sizeof(*ptr)) ) (initialization)

It definitely not, what you are thinking.

Because :

ptr is of type  (float *)  which is a pointer.
*ptr is of type  (float)   which is not a pointer,  so it can't points to the address given by malloc()

You can consider your first statement like this:

float  *   ptr = malloc(sizeof(*ptr);   // I think this will clear your doubt.
answer Nov 6, 2014 by Arshad Khan
–1 vote

in first case the created memory will be saved at the *ptr but in second case ptr will be the memory address of the newly created memory.

answer Nov 6, 2014 by Kumar Shishir
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