Why does `long long` behave differently than expected in C/C ?

Understanding Long Long in C/C

When working with various data types in C and C , it's crucial to understand the nuances of each type. One common misconception is the behavior of long long.

Consider the following code snippet:

#include <stdio.h>

int main()
{
    int  num1 = 1000000000;
    long num2 = 1000000000;
    long long num3;
    //num3 = 100000000000;
    long long num4 = ~0;

    printf("%u %u %u", sizeof(num1), sizeof(num2), sizeof(num3));
    printf("%d %ld %lld %llu", num1, num2, num3, num4);
    return 0;
}</stdio.h>

Compiling this code raises an error when uncommenting the line assigning 100000000000 to num3: "integer constant is too large for long type." However, executing the code with the commented line still prints values larger than 10000000000.

This behavior stems from a misconception about type inference. The literal 100000000000 is an integer constant, but its value exceeds the range of the int data type (32 bits). Therefore, it's intended as a long type constant. However, by default, C and C consider such literals as int, leading to the error.

To resolve this, it's necessary to explicitly specify the type of the literal using a suffix. The LL suffix declares num3 as a long long type:

long long num3 = 100000000000LL;

This change allows the code to compile successfully without any errors or unexpected behavior.

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