API to check maximum value of any data type exceeded

Is there any API to check if any number exceeds it's range?

My number is stored as string. char *ptr = "123456789"

API should do: int a = api(ptr, long) if a==-1 suppose value exceeds.

Please note: We can't parse the string and check because it will automatically wrap it to the other side, and make it within the range.

开发者_开发技巧Thanks in advance

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Please checkout strtol and strtoul.

See this example:

#include <stdlib.h>
#include <errno.h>
#include <limits.h>
int main (int argc, char const* argv[])
{
    char a[] = "123";
    char c[] = "123134123412341234";
    long b, d;
    errno = 0;
    b = strtol(a, NULL, 10);
    if((b == LONG_MAX || b == LONG_MIN) && errno == ERANGE ){
        printf("%s Out of range\n", a);
    }
    errno = 0;
    d = strtol(c, NULL, 10);
    if((d == LONG_MAX || d == LONG_MIN) && errno == ERANGE ){
        printf("%s Out of range\n", c);
    }
    return 0;
}

Edits:

1. Changed int to long for b and d.
2. Setting errno to 0 before calling into c library.
3. Checking for LONG_MIN also for errors.
4. Changed the order for checks (according to comment below)

---

Well, you can still check. Just build up the number and check to see if the number indeed became bigger or smaller.

int i = 0; // pos indicator
int r = 0; // result
int c = 0; // check
while(ptr[i])
{
    c = r;
    r = r * 10 + (ptr[i++] - '0');
    if(r < c)
        print("overflow happened!\n");
}

Edit: Note that this won't work with unsigned datatypes as it's too easy to overflow far enough to still pass the check.

---

Just use strol() or strtoll() and check errno. For smaller datatypes you need to make a very simple function that compares against USHRT_MAX, UINT_MAX etc from limits.h.

man strol and man limits.h for more information.