"assignment discards 'const' qualifier" error on non-const pointer

Question

In the following function:

char *mystrtok(const char *input, const char *delim,char *rest) {
    int i;
    for (i = 0; input[i] != *delim && input[i] != '\0'; ++i) {
        continue;
    }
    char *result = malloc(sizeof(char) * (i + 2));
    memcpy(result, input, i + 1);
    result[i + 1] = '\0';
    if (input[i + 1] != '\0') 
        rest = input + i + 2;
    else
        rest = NULL;
    return result;
}

I am getting assignment discards 'const' qualifier from pointer target type for the line rest = input + i + 2, however, as you can see, rest is not a constant pointer. What am I doing wrong here?

Solution 1

input is a pointer to a constant char, and you're assigning it to a pointer to a non-constant char. This here might be an interesting reading for you.

Solution 2

you could also cast your 'input' variable with a (char*) type which would resolve the warning. just be careful using explicit casts like this so as not to modify constants themselves.

rest = (char*)input + i + 2;

Comments

[littleadv]

@yasar11732 then you need char * const - the pointer is constant, not what it points to.

[flarn2006]

I tried that and I still get the warning.