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Add working example for E0617 explanation #72605

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May 29, 2020
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11 changes: 11 additions & 0 deletions src/librustc_error_codes/error_codes/E0617.md
Original file line number Diff line number Diff line change
Expand Up @@ -17,3 +17,14 @@ Certain Rust types must be cast before passing them to a variadic function,
because of arcane ABI rules dictated by the C standard. To fix the error,
cast the value to the type specified by the error message (which you may need
to import from `std::os::raw`).

In this case, `c_double` has the same size as `f64` so we can use it directly:

```no_run
# extern {
# fn printf(c: *const i8, ...);
# }
unsafe {
printf(::std::ptr::null(), 0f64); // ok!
}
```