在C中验证整数参数

Question

I was told one of the best practice with Functions with parameters is to perform parameter validation.
So for string checking null or empty and so on.

I am creating a List and for that creating a node which accepts integer value. I am checking the value against INT_MIN and INT_MAX but from what I read int value is always going to be between this. If I pass a long long val, in the called function with signature node* create(int val) - value gets converted to int range and falls within.

Question : if val of long is being passed, is there a way to detect it and not let the node be created ? Currently it gets created

Question : for a standard int what else checking of parameter do I need to perform to write a robust code ?

My code Snippet

long long vall = 88888888888888; 
create(vall);     // for such case I don't want node to be created

node* create(int val)
{
    if (val <= INT_MIN || val >= INT_MAX)
    {
        printf(" values are out of range");
    }
    node *pnode = (node *)malloc(sizeof(node));
    if(pnode == NULL)
    {
        printf(" node creation failed \n");
    }

    pnode->pnext = NULL;
    pnode->val = val;

    return pnode;
}

Answer 1

if val of long is being passed, is there a way to detect it and not let the node be created ?

Change function signature to long or long long , etc.

// declare/define function first
node* create(long long val);

long long vall = 88888888888888; 
create(vall);     // for such case I don't want node to be created

node* create(long long val) {
    // if (val <= INT_MIN || val >= INT_MAX) {
    if (val < INT_MIN || val > INT_MAX) {
        fprintf(stderr, " %lld out of int range\n", val);

        return NULL;
        // Return or exit, do not continue with the following code 
    }

    // node *pnode = (node *)malloc(sizeof(node));
    // Suggest alternative
    node *pnode = malloc(sizeof *pnode);
    ...
    // Adding an explicit cast useful to quiet pedantic warnings
    pnode->val = (int) val;
    ...

Note: With original code, many compilers with all warnings enabled will warn about the below (without knowing the value of vall ) as a narrowing of range.

node* create(int val)
long long vall = ...; 
create(vall);

for a standard int what else checking of parameter do I need to perform to write a robust code ?

Nothing, unless the function can only use a sub-range of int . All int values are in the range [INT_MIN ... IN_MAX] . @Eugene Sh.

Answer 2

You may create one more function with the same name but different arguments list:

node* create(long long val);

If you pass a value of type long long , this function will run, not node* create(int val); . So, you can handle the case, when you pass long as a parameter, through creating another function.

As for your second questinon, I should say, that you don't need to check your int value against INT_MIN and INT_MAX boundaries, because it will never be out of these bounds. INT_MAX and INT_MIN are ACTUAL BOUNDARIES OF int TYPE ITSELF.

Check your int value considering your needs (needs of your function).

You need to check passed strings for NULL , because if you try to access such string, your program will collapse. But when you pass an int value, it will have an assigned value anyway.