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fix example code for E0617 #87435

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Jul 29, 2021
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fix example code for E0617 #87435

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11 changes: 7 additions & 4 deletions compiler/rustc_error_codes/src/error_codes/E0617.md
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,13 @@ Attempted to pass an invalid type of variable into a variadic function.
Erroneous code example:

```compile_fail,E0617
# use std::os::raw::{c_char, c_int};
extern "C" {
fn printf(c: *const i8, ...);
fn printf(format: *const c_char, ...) -> c_int;
}
unsafe {
printf(::std::ptr::null(), 0f32);
printf("%f\n\0".as_ptr() as _, 0f32);
// error: cannot pass an `f32` to variadic function, cast to `c_double`
}
```
Expand All @@ -21,10 +22,12 @@ 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
# use std::os::raw::{c_char, c_int};
# extern "C" {
# fn printf(c: *const i8, ...);
# fn printf(format: *const c_char, ...) -> c_int;
# }
unsafe {
printf(::std::ptr::null(), 0f64); // ok!
printf("%f\n\0".as_ptr() as _, 0f64); // ok!
}
```