1 Attempted to pass an invalid type of variable into a variadic function.
3 Erroneous code example:
6 # use std::os::raw::{c_char, c_int};
8 fn printf(format: *const c_char, ...) -> c_int;
12 printf("%f\n\0".as_ptr() as _, 0f32);
13 // error: cannot pass an `f32` to variadic function, cast to `c_double`
17 Certain Rust types must be cast before passing them to a variadic function,
18 because of arcane ABI rules dictated by the C standard. To fix the error,
19 cast the value to the type specified by the error message (which you may need
20 to import from `std::os::raw`).
22 In this case, `c_double` has the same size as `f64` so we can use it directly:
25 # use std::os::raw::{c_char, c_int};
27 # fn printf(format: *const c_char, ...) -> c_int;
31 printf("%f\n\0".as_ptr() as _, 0f64); // ok!