warning: `extern` block uses type `Option<TransparentNoNiche>`, which is not FFI-safe
  --> $DIR/clashing-extern-fn.rs:429:55
   |
LL |             fn hidden_niche_transparent_no_niche() -> Option<TransparentNoNiche>;
   |                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
   = note: enum has no representation hint
   = note: `#[warn(improper_ctypes)]` on by default

warning: `extern` block uses type `Option<UnsafeCell<NonZero<usize>>>`, which is not FFI-safe
  --> $DIR/clashing-extern-fn.rs:433:46
   |
LL |             fn hidden_niche_unsafe_cell() -> Option<UnsafeCell<NonZero<usize>>>;
   |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not FFI-safe
   |
   = help: consider adding a `#[repr(C)]`, `#[repr(transparent)]`, or integer `#[repr(...)]` attribute to this enum
   = note: enum has no representation hint

warning: `clash` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:14:13
   |
LL |             fn clash(x: u8);
   |             --------------- `clash` previously declared here
...
LL |             fn clash(x: u64);
   |             ^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(u8)`
              found `unsafe extern "C" fn(u64)`
note: the lint level is defined here
  --> $DIR/clashing-extern-fn.rs:4:9
   |
LL | #![warn(clashing_extern_declarations)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: `extern_link_name` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:52:9
   |
LL |     #[link_name = "extern_link_name"]
   |     --------------------------------- `extern_link_name` previously declared here
...
LL |         fn extern_link_name(x: u32);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(i16)`
              found `unsafe extern "C" fn(u32)`

warning: `some_other_extern_link_name` redeclares `some_other_new_name` with a different signature
  --> $DIR/clashing-extern-fn.rs:55:9
   |
LL |     fn some_other_new_name(x: i16);
   |     ------------------------------ `some_other_new_name` previously declared here
...
LL |         #[link_name = "some_other_new_name"]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(i16)`
              found `unsafe extern "C" fn(u32)`

warning: `other_both_names_different` redeclares `link_name_same` with a different signature
  --> $DIR/clashing-extern-fn.rs:59:9
   |
LL |     #[link_name = "link_name_same"]
   |     ------------------------------- `link_name_same` previously declared here
...
LL |         #[link_name = "link_name_same"]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(i16)`
              found `unsafe extern "C" fn(u32)`

warning: `different_mod` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:72:9
   |
LL |         fn different_mod(x: u8);
   |         ----------------------- `different_mod` previously declared here
...
LL |         fn different_mod(x: u64);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(u8)`
              found `unsafe extern "C" fn(u64)`

warning: `variadic_decl` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:82:9
   |
LL |     fn variadic_decl(x: u8, ...);
   |     ---------------------------- `variadic_decl` previously declared here
...
LL |         fn variadic_decl(x: u8);
   |         ^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(u8, ...)`
              found `unsafe extern "C" fn(u8)`

warning: `weigh_banana` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:142:13
   |
LL |             fn weigh_banana(count: *const Banana) -> u64;
   |             -------------------------------------------- `weigh_banana` previously declared here
...
LL |             fn weigh_banana(count: *const Banana) -> u64;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(*const one::Banana) -> u64`
              found `unsafe extern "C" fn(*const three::Banana) -> u64`

warning: `draw_point` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:171:13
   |
LL |             fn draw_point(p: Point);
   |             ----------------------- `draw_point` previously declared here
...
LL |             fn draw_point(p: Point);
   |             ^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn(sameish_members::a::Point)`
              found `unsafe extern "C" fn(sameish_members::b::Point)`

warning: `origin` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:197:13
   |
LL |             fn origin() -> Point3;
   |             --------------------- `origin` previously declared here
...
LL |             fn origin() -> Point3;
   |             ^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> same_sized_members_clash::a::Point3`
              found `unsafe extern "C" fn() -> same_sized_members_clash::b::Point3`

warning: `transparent_incorrect` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:220:13
   |
LL |             fn transparent_incorrect() -> T;
   |             ------------------------------- `transparent_incorrect` previously declared here
...
LL |             fn transparent_incorrect() -> isize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> T`
              found `unsafe extern "C" fn() -> isize`

warning: `missing_return_type` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:259:13
   |
LL |             fn missing_return_type() -> usize;
   |             --------------------------------- `missing_return_type` previously declared here
...
LL |             fn missing_return_type();
   |             ^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> usize`
              found `unsafe extern "C" fn()`

warning: `non_zero_usize` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:277:13
   |
LL |             fn non_zero_usize() -> core::num::NonZero<usize>;
   |             ------------------------------------------------ `non_zero_usize` previously declared here
...
LL |             fn non_zero_usize() -> usize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> NonZero<usize>`
              found `unsafe extern "C" fn() -> usize`

warning: `non_null_ptr` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:279:13
   |
LL |             fn non_null_ptr() -> core::ptr::NonNull<usize>;
   |             ---------------------------------------------- `non_null_ptr` previously declared here
...
LL |             fn non_null_ptr() -> *const usize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> NonNull<usize>`
              found `unsafe extern "C" fn() -> *const usize`

warning: `option_non_zero_usize_incorrect` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:373:13
   |
LL |             fn option_non_zero_usize_incorrect() -> usize;
   |             --------------------------------------------- `option_non_zero_usize_incorrect` previously declared here
...
LL |             fn option_non_zero_usize_incorrect() -> isize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> usize`
              found `unsafe extern "C" fn() -> isize`

warning: `option_non_null_ptr_incorrect` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:375:13
   |
LL |             fn option_non_null_ptr_incorrect() -> *const usize;
   |             -------------------------------------------------- `option_non_null_ptr_incorrect` previously declared here
...
LL |             fn option_non_null_ptr_incorrect() -> *const isize;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> *const usize`
              found `unsafe extern "C" fn() -> *const isize`

warning: `hidden_niche_transparent_no_niche` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:429:13
   |
LL |             fn hidden_niche_transparent_no_niche() -> usize;
   |             ----------------------------------------------- `hidden_niche_transparent_no_niche` previously declared here
...
LL |             fn hidden_niche_transparent_no_niche() -> Option<TransparentNoNiche>;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> usize`
              found `unsafe extern "C" fn() -> Option<TransparentNoNiche>`

warning: `hidden_niche_unsafe_cell` redeclared with a different signature
  --> $DIR/clashing-extern-fn.rs:433:13
   |
LL |             fn hidden_niche_unsafe_cell() -> usize;
   |             -------------------------------------- `hidden_niche_unsafe_cell` previously declared here
...
LL |             fn hidden_niche_unsafe_cell() -> Option<UnsafeCell<NonZero<usize>>>;
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this signature doesn't match the previous declaration
   |
   = note: expected `unsafe extern "C" fn() -> usize`
              found `unsafe extern "C" fn() -> Option<UnsafeCell<NonZero<usize>>>`

warning: 19 warnings emitted