Question

I have a structure and a enum,

    struct __value
    {
       int a;
       enum xsd__boolean *ptr;
    } 
    enum xsd__boolean
    {
      __true = 1,
      __false = 0
    };

Is this the right way of doing a malloc to enum and assigning the value,I want to assign the value of __true or __false to *__StructPtr->ptr.Will the size of __true be same as that of int ?

struct __value *__StructPtr;
__StructPtr->ptr = (int *)malloc(sizeof(int)); 
*__StructPtr->ptr = __true;

Is this is the right way, please provide me some insight about this with some example.

Answer 1

struct __value *__StructPtr;
__StructPtr->ptr = (int *)malloc(sizeof(int)); 
*__StructPtr->ptr = __true;

This is incorrect. Your __StructPtr pointer is not pointed at allocated memory, and thus assigning through the pointer leads to memory corruption.

The correct way is something like:

struct __value __StructPtr;
__StructPtr.ptr = malloc(sizeof(*__StructPtr.ptr)); 
*__StructPtr.ptr = __true;

In this case, you’re allocating a struct __value on the stack, and then dynamically creating the memory pointed to by __StructPtr->ptr.

If you wanted to allocate __StructPtr and the memory __StructPtr->ptr points at both dynamically, try:

struct __value *__StructPtr;
__StructPtr = malloc(sizeof(*__StructPtr));
__StructPtr->ptr = malloc(sizeof(*__StructPtr->ptr)); 
*__StructPtr->ptr = __true;