Indeed, FLT_EPSILON is not a one-size-fits-all solution, but it's good enough for frequent case of comparing big enough numbers, which is not covered by regular ==. So it's a convenience/correctness trade-off I'm ready to make.
// FLT_EPSILON == 0.01
equal(4.999, 5); // true
4.999 == 5; // false
But it's impossible to have a number that's 0.00000011920929 less than 5.0, or 0.00000011920929 more than 5.0, because the floats with enough magnitude to represent 5 are spaced further apart than that. Only numbers with magnitude < 2 are spaced close enough together.
In other words, the only 32-bit float that's within ±0.00000011920929 of 5.0 is 5.0 itself.
Gotta research now where the 0.00000011920929 number comes from...
Is it representable as a non-trivial ratio of integers?