diff --git a/tests/ui/functions.rs b/tests/ui/functions.rs
index 7e2e083e298..271754cb06e 100644
--- a/tests/ui/functions.rs
+++ b/tests/ui/functions.rs
@@ -31,12 +31,12 @@ fn bad_multiline(
 extern "C" fn extern_fn(
     _one: u32,
     _two: u32,
-    _three: &str,
+    _three: *const u8,
     _four: bool,
     _five: f32,
     _six: f32,
     _seven: bool,
-    _eight: (),
+    _eight: *const std::ffi::c_void,
 ) {
 }
 
diff --git a/tests/ui/needless_pass_by_value.rs b/tests/ui/needless_pass_by_value.rs
index ca94daa24e8..e93a7fe2985 100644
--- a/tests/ui/needless_pass_by_value.rs
+++ b/tests/ui/needless_pass_by_value.rs
@@ -11,6 +11,7 @@
 use std::borrow::Borrow;
 use std::collections::HashSet;
 use std::convert::AsRef;
+use std::mem::MaybeUninit;
 
 // `v` should be warned
 // `w`, `x` and `y` are allowed (moved or mutated)
@@ -111,8 +112,8 @@ trait FalsePositive {
 }
 
 // shouldn't warn on extern funcs
-extern "C" fn ext(x: String) -> usize {
-    x.len()
+extern "C" fn ext(x: MaybeUninit<usize>) -> usize {
+    unsafe { x.assume_init() }
 }
 
 // whitelist RangeArgument
diff --git a/tests/ui/needless_pass_by_value.stderr b/tests/ui/needless_pass_by_value.stderr
index 6cf517c22ef..37241dbb409 100644
--- a/tests/ui/needless_pass_by_value.stderr
+++ b/tests/ui/needless_pass_by_value.stderr
@@ -1,5 +1,5 @@
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:17:23
+  --> $DIR/needless_pass_by_value.rs:18:23
    |
 LL | fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T> {
    |                       ^^^^^^ help: consider changing the type to: `&[T]`
@@ -7,55 +7,55 @@ LL | fn foo<T: Default>(v: Vec<T>, w: Vec<T>, mut x: Vec<T>, y: Vec<T>) -> Vec<T
    = note: `-D clippy::needless-pass-by-value` implied by `-D warnings`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:31:11
+  --> $DIR/needless_pass_by_value.rs:32:11
    |
 LL | fn bar(x: String, y: Wrapper) {
    |           ^^^^^^ help: consider changing the type to: `&str`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:31:22
+  --> $DIR/needless_pass_by_value.rs:32:22
    |
 LL | fn bar(x: String, y: Wrapper) {
    |                      ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:37:71
+  --> $DIR/needless_pass_by_value.rs:38:71
    |
 LL | fn test_borrow_trait<T: Borrow<str>, U: AsRef<str>, V>(t: T, u: U, v: V) {
    |                                                                       ^ help: consider taking a reference instead: `&V`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:49:18
+  --> $DIR/needless_pass_by_value.rs:50:18
    |
 LL | fn test_match(x: Option<Option<String>>, y: Option<Option<String>>) {
    |                  ^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&Option<Option<String>>`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:62:24
+  --> $DIR/needless_pass_by_value.rs:63:24
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
    |                        ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:62:36
+  --> $DIR/needless_pass_by_value.rs:63:36
    |
 LL | fn test_destructure(x: Wrapper, y: Wrapper, z: Wrapper) {
    |                                    ^^^^^^^ help: consider taking a reference instead: `&Wrapper`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:78:49
+  --> $DIR/needless_pass_by_value.rs:79:49
    |
 LL | fn test_blanket_ref<T: Foo, S: Serialize>(_foo: T, _serializable: S) {}
    |                                                 ^ help: consider taking a reference instead: `&T`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:80:18
+  --> $DIR/needless_pass_by_value.rs:81:18
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                  ^^^^^^ help: consider taking a reference instead: `&String`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:80:29
+  --> $DIR/needless_pass_by_value.rs:81:29
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                             ^^^^^^
@@ -70,13 +70,13 @@ LL |     let _ = t.to_string();
    |             ^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:80:40
+  --> $DIR/needless_pass_by_value.rs:81:40
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                                        ^^^^^^^^ help: consider taking a reference instead: `&Vec<i32>`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:80:53
+  --> $DIR/needless_pass_by_value.rs:81:53
    |
 LL | fn issue_2114(s: String, t: String, u: Vec<i32>, v: Vec<i32>) {
    |                                                     ^^^^^^^^
@@ -91,85 +91,85 @@ LL |     let _ = v.to_owned();
    |             ^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:93:12
+  --> $DIR/needless_pass_by_value.rs:94:12
    |
 LL |         s: String,
    |            ^^^^^^ help: consider changing the type to: `&str`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:94:12
+  --> $DIR/needless_pass_by_value.rs:95:12
    |
 LL |         t: String,
    |            ^^^^^^ help: consider taking a reference instead: `&String`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:103:23
+  --> $DIR/needless_pass_by_value.rs:104:23
    |
 LL |     fn baz(&self, _u: U, _s: Self) {}
    |                       ^ help: consider taking a reference instead: `&U`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:103:30
+  --> $DIR/needless_pass_by_value.rs:104:30
    |
 LL |     fn baz(&self, _u: U, _s: Self) {}
    |                              ^^^^ help: consider taking a reference instead: `&Self`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:125:24
+  --> $DIR/needless_pass_by_value.rs:126:24
    |
 LL | fn bar_copy(x: u32, y: CopyWrapper) {
    |                        ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:123:1
+  --> $DIR/needless_pass_by_value.rs:124:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:131:29
+  --> $DIR/needless_pass_by_value.rs:132:29
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:123:1
+  --> $DIR/needless_pass_by_value.rs:124:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:131:45
+  --> $DIR/needless_pass_by_value.rs:132:45
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:123:1
+  --> $DIR/needless_pass_by_value.rs:124:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:131:61
+  --> $DIR/needless_pass_by_value.rs:132:61
    |
 LL | fn test_destructure_copy(x: CopyWrapper, y: CopyWrapper, z: CopyWrapper) {
    |                                                             ^^^^^^^^^^^ help: consider taking a reference instead: `&CopyWrapper`
    |
 help: consider marking this type as Copy
-  --> $DIR/needless_pass_by_value.rs:123:1
+  --> $DIR/needless_pass_by_value.rs:124:1
    |
 LL | struct CopyWrapper(u32);
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:143:40
+  --> $DIR/needless_pass_by_value.rs:144:40
    |
 LL | fn some_fun<'b, S: Bar<'b, ()>>(_item: S) {}
    |                                        ^ help: consider taking a reference instead: `&S`
 
 error: this argument is passed by value, but not consumed in the function body
-  --> $DIR/needless_pass_by_value.rs:148:20
+  --> $DIR/needless_pass_by_value.rs:149:20
    |
 LL | fn more_fun(_item: impl Club<'static, i32>) {}
    |                    ^^^^^^^^^^^^^^^^^^^^^^^ help: consider taking a reference instead: `&impl Club<'static, i32>`