Question

There is this code.

#include <iostream>
#include <climits>
enum e  {zero,one};
void main()
{
    e num=(e)INT_MAX;
    std::cout<<num;
}

Is it defined by the standart that output will be 2147483647?(on condition sizeof(int)=4 bytes)

Answer 1

No; when converting an integer to an enumeration, the enumeration value is only specified if the integer value is within range. From the standard:

7.2/10 An expression of arithmetic or enumeration type can be converted to an enumeration type explicitly. The
value is unchanged if it is in the range of enumeration values of the enumeration type; otherwise the resulting
enumeration value is unspecified.

where the “range” is described in a rather complicated manner in 7.2/7, and essentially goes up to the smallest value of 2^M-1 that’s no less than the largest defined value.

The compiler is allowed to use any integer type to represent the enumeration, as long as it’s large enough to hold all the enumeration values; so in this case, it’s free to use a smaller type than int, such as char. Also, INT_MAX is only guaranteed to be at least 32767.