diff --git a/tests/ui/abi/segfault-no-out-of-stack.rs b/tests/ui/abi/segfault-no-out-of-stack.rs
index fb1f8303f9ffd..113c82c30e927 100644
--- a/tests/ui/abi/segfault-no-out-of-stack.rs
+++ b/tests/ui/abi/segfault-no-out-of-stack.rs
@@ -1,31 +1,29 @@
 //@ run-pass
-
-#![allow(unused_imports)]
 //@ ignore-wasm32 can't run commands
 //@ ignore-sgx no processes
 //@ ignore-fuchsia must translate zircon signal to SIGSEGV/SIGBUS, FIXME (#58590)
-#![feature(rustc_private)]
 
-extern crate libc;
+#![feature(rustc_private)]
 
 use std::env;
+use std::ffi::c_char;
 use std::process::{Command, ExitStatus};
 
 #[link(name = "rust_test_helpers", kind = "static")]
 extern "C" {
-    fn rust_get_null_ptr() -> *mut ::libc::c_char;
+    fn rust_get_null_ptr() -> *mut c_char;
 }
 
 #[cfg(unix)]
-fn check_status(status: std::process::ExitStatus) {
-    use libc;
+fn check_status(status: ExitStatus) {
+    extern crate libc;
     use std::os::unix::process::ExitStatusExt;
 
     assert!(status.signal() == Some(libc::SIGSEGV) || status.signal() == Some(libc::SIGBUS));
 }
 
 #[cfg(not(unix))]
-fn check_status(status: std::process::ExitStatus) {
+fn check_status(status: ExitStatus) {
     assert!(!status.success());
 }
 
diff --git a/tests/ui/attributes/unix_sigpipe/unix_sigpipe-and-child-processes.rs b/tests/ui/attributes/unix_sigpipe/unix_sigpipe-and-child-processes.rs
index f96bd634876fd..9d1bd9f9607ec 100644
--- a/tests/ui/attributes/unix_sigpipe/unix_sigpipe-and-child-processes.rs
+++ b/tests/ui/attributes/unix_sigpipe/unix_sigpipe-and-child-processes.rs
@@ -11,10 +11,8 @@
 // processes with and without the attribute. Search for
 // `unix_sigpipe_attr_specified()` in the code base to learn more.
 
-#![feature(rustc_private)]
 #![cfg_attr(any(sig_dfl, sig_ign, inherit), feature(unix_sigpipe))]
 
-extern crate libc;
 extern crate sigpipe_utils;
 
 use sigpipe_utils::*;
diff --git a/tests/ui/extern-flag/auxiliary/panic_handler.rs b/tests/ui/extern-flag/auxiliary/panic_handler.rs
index a625761a838a8..5ca32fa992b05 100644
--- a/tests/ui/extern-flag/auxiliary/panic_handler.rs
+++ b/tests/ui/extern-flag/auxiliary/panic_handler.rs
@@ -5,7 +5,9 @@
 // Rust programs link necessary system libraries via `#[link()]`
 // attributes in the `libc` crate. `libc` is a dependency of `std`,
 // but as we are `#![no_std]`, we need to include it manually.
+// Except on windows-msvc.
 #![feature(rustc_private)]
+#[cfg(not(all(windows, target_env = "msvc")))]
 extern crate libc;
 
 #[panic_handler]
diff --git a/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014-2.rs b/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014-2.rs
index 4944de0b82f33..eb512bb40aa37 100644
--- a/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014-2.rs
+++ b/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014-2.rs
@@ -1,31 +1,28 @@
+// Test that println! to a closed stdout does not panic.
+// On Windows, close via SetStdHandle to 0.
 //@ run-pass
-#![allow(dead_code)]
 
 #![feature(rustc_private)]
 
-extern crate libc;
-
-type DWORD = u32;
-type HANDLE = *mut u8;
-type BOOL = i32;
-
-#[cfg(windows)]
-extern "system" {
-    fn SetStdHandle(nStdHandle: DWORD, nHandle: HANDLE) -> BOOL;
-}
-
 #[cfg(windows)]
 fn close_stdout() {
+    type DWORD = u32;
+    type HANDLE = *mut u8;
+    type BOOL = i32;
+
+    extern "system" {
+        fn SetStdHandle(nStdHandle: DWORD, nHandle: HANDLE) -> BOOL;
+    }
+
     const STD_OUTPUT_HANDLE: DWORD = -11i32 as DWORD;
     unsafe { SetStdHandle(STD_OUTPUT_HANDLE, 0 as HANDLE); }
 }
 
-#[cfg(windows)]
+#[cfg(not(windows))]
+fn close_stdout() {}
+
 fn main() {
     close_stdout();
     println!("hello");
     println!("world");
 }
-
-#[cfg(not(windows))]
-fn main() {}
diff --git a/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014.rs b/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014.rs
index cc2d9bad02983..950c4dee329ff 100644
--- a/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014.rs
+++ b/tests/ui/rfcs/rfc-1014-stdout-existential-crisis/rfc-1014.rs
@@ -1,28 +1,27 @@
+// Test that println! to a closed stdout does not panic.
+// On Windows, close via CloseHandle.
 //@ run-pass
-#![allow(dead_code)]
 //@ ignore-sgx no libc
 
 #![feature(rustc_private)]
 
-extern crate libc;
-
-type DWORD = u32;
-type HANDLE = *mut u8;
-
-#[cfg(windows)]
-extern "system" {
-    fn GetStdHandle(which: DWORD) -> HANDLE;
-    fn CloseHandle(handle: HANDLE) -> i32;
-}
-
 #[cfg(windows)]
 fn close_stdout() {
+    type DWORD = u32;
+    type HANDLE = *mut u8;
+
+    extern "system" {
+        fn GetStdHandle(which: DWORD) -> HANDLE;
+        fn CloseHandle(handle: HANDLE) -> i32;
+    }
+
     const STD_OUTPUT_HANDLE: DWORD = -11i32 as DWORD;
     unsafe { CloseHandle(GetStdHandle(STD_OUTPUT_HANDLE)); }
 }
 
 #[cfg(not(windows))]
 fn close_stdout() {
+    extern crate libc;
     unsafe { libc::close(1); }
 }