Initialization Discards Qualifiers from Pointer Target Type
I'm Trying to Print the List of a Singly Linked List That I Referred to in Link Text. It Works, but I Do Get the Compiler Warnings: Initialization Discards...
I'm trying to print the list of a singly linked list that I referred to in link text. It works, but I do get the compiler warnings:
Initialization discards qualifiers from pointer target type
(on declaration of start = head) and
return discards qualifiers from pointer target type
(on return statement) in this code:
/* Prints singly linked list and returns head pointer */
LIST *PrintList(const LIST *head)
{
LIST *start = head;
for (; start != NULL; start = start->next)
printf("%15s %d ea\n", head->str, head->count);
return head;
}
I am using XCode. Any thoughts?
2 Answers
It's this part:
LIST *start = head;
The parameter for the function is a pointer to a constant, const LIST *head; this means you cannot change what it is pointing to. However, the pointer above is to non-const; you could dereference it and change it.
It needs to be const as well:
const LIST *start = head;
The same applies to your return type.
All the compiler is saying is: "Hey, you said to the caller 'I won't change anything', but you're opening up opportunities for that."
In following function, would get the warning that you encountered with.
void test(const char *str) {
char *s = str;
}
There are 3 choices:
Remove the const modifier of param:
void test(char *str) { char *s = str; }Declare the target variable also as const:
void test(const char *str) { const char *s = str; }Use a type convert:
void test(const char *str) { char *s = (char *)str; }
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