int to float conversion produces a warning?

Question

It's surprising for me to see that even when the value can be converted, an int to float conversion always give a warning. Why is this?

int i = 0;
float f = 0; // warning here

// I thought this was an implicit conversion,
// meaning it is convertible with no warnings.
f = i;      // another warning here

The warning is:

warning C4244: '=' : conversion from 'int' to 'float', possible loss of data

Answer 1

I answered a similar question here:

Why does GCC warn against this implicit conversion?

The reason is that an int needs to be rounded when it is casted into a float because float cannot contain all the precision of an int in this case.

In your case, a float only has about 24 bits of precision. While an int has 32 bits of precision, therefore, some precision is loss by this cast, hence the warning.