Dervin Thunk Dervin Thunk -4 years ago 107
C Question

long long is 8 bytes, but I get integer overflow?

Suppose

long long b = 5*1024*1024*1024; // 5 gigs, small enough for 64 bits
printf ("%lu\n",sizeof(long long)); // prints 8 (bytes) = 64 bits


but the compiler complains:

warning: integer overflow in expression [-Woverflow]


Why does it overflow, what am I missing?

Answer Source

Because the numbers on the right hand side are of type int, not long long, so int arithmetic is performed in the expression, leading to an overflow.

If you add LL to one of them, it'll promote them all.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download