Bound checking bug with unsigned long long

[Trung Nguyen]

I'm testing cppcheck 2.3 with some code and there seems to be a bug with array bound checking for unsigned long long. In the snippet of code below, if variable i is unsigned int there is no error flagged by cppcheck but if i is unsigned long long, it spits out an error. Is this a known issue?

#include <stdio.h>

int main ()
{

//    unsigned int i = (unsigned int)~0;
    unsigned long long i = (unsigned long long)~0;
    int myArray[10];

    if (i > 9) return -1;
    myArray[i] = 0;
}

test.c:11:12: error: Array 'myArray[10]' accessed at index -1, which is out of bounds. [negativeIndex]
myArray[i] = 0;
^
test.c:7:28: note: Assignment 'i=(unsigned long long)~0', assigned value is -1
unsigned long long i = (unsigned long long)~0;
^
test.c:10:11: note: Assuming condition is false
if (i > 9) return -1;
^
test.c:11:12: note: Negative array index
myArray[i] = 0;

The error is also funny (i.e. negative index) since the variable is unsigned but it is out-of-bound access if you try to access 0xFFFFFFFFFFFFFFFF element.

[CHR]

I have a feeling that this problem is also related to https://trac.cppcheck.net/ticket/10150.
cppcheck seems to treat uint64_t as a signed type. Assigning the literal 18446744073709551615 gives the same warning.