取消引用 NULL 指针 C++

Question

I get the warning: Derefering NULL pointer 'ch' on lines 2, 4

I don't understand why. Can someone help me out?

char *my_alloc(size_t size) {
   char *ch  = (char *)malloc(size);
   //FIXED: If malloc fails -> exit program
   if(*ch == NULL){
       exit(0);
   }
   return ch;
}

Answer 1

if(ch == NULL) is what you need

you dereference ch at the code *ch inside if

---

ch == NULL check whether ch is NULL

*ch == NULL check whether the item point by ch is NULL

Answer 2

For c++ (what you report using in your question) the answer is

char *ch  = new char[size];

followed by a delete[] ch at some point.

You then don't need to check if the result is null as it will throw if it failed.