Number of bits in a data type

Question

I have two tasks for an assignment, one return the number of bits in type int on any machine. I thought I would write my function like so:

int CountIntBitsF() {         


        

Answer 1

With g++ -O2 this function evaluates to an inline constant:

#include 
#include 
#include 
#include 

template 
size_t num_bits()
{
    return sizeof (T) * (CHAR_BIT);
}

int main()
{
    printf("uint8_t : %d\n", num_bits());
    printf("size_t : %d\n", num_bits());
    printf("long long : %d\n", num_bits());
    printf("void* : %d\n", num_bits());
    printf("bool : %d\n", num_bits());
    printf("float : %d\n", num_bits());
    printf("double : %d\n", num_bits());
    printf("long double : %d\n", num_bits());

    return 0;
}

outputs:

uint8_t : 8
size_t : 32
long long : 64
void* : 32
bool : 8
float : 32
double : 64
long double : 96

Generated X86 32-bit assember:

---SNIP---

movl    $32, 8(%esp)      <--- const $32
movl    $.LC1, 4(%esp)
movl    $1, (%esp)
call    __printf_chk
movl    $64, 8(%esp)      <--- const $64
movl    $.LC2, 4(%esp)
movl    $1, (%esp)
call    __printf_chk

---SNIP---