Remove Windows dependency on libc

Author: saethlin

library/core/src/primitive_docs.rs

@@ -537,18 +537,18 @@ impl () {}
 /// ## 4. Get it from C.
 ///
 /// ```
-/// # #![feature(rustc_private)]
-/// #[allow(unused_extern_crates)]
-/// extern crate libc;
-///
+/// # mod libc {
+/// # pub unsafe fn malloc(_size: usize) -> *mut u8 { core::ptr::NonNull::dangling().as_ptr() }
+/// # pub unsafe fn free(mem: *mut core::ffi::c_void) {}
+/// # }
 /// use std::mem;
 ///
 /// unsafe {
 ///     let my_num: *mut i32 = libc::malloc(mem::size_of::<i32>()) as *mut i32;
 ///     if my_num.is_null() {
 ///         panic!("failed to allocate memory");
 ///     }
-///     libc::free(my_num as *mut libc::c_void);
+///     libc::free(my_num as *mut core::ffi::c_void);
 /// }
 /// ```
 ///

library/std/Cargo.toml

@@ -33,9 +33,6 @@ addr2line = { version = "0.21.0", optional = true, default-features = false }
 [target.'cfg(not(all(windows, target_env = "msvc")))'.dependencies]
 libc = { version = "0.2.153", default-features = false, features = ['rustc-dep-of-std'], public = true }
 
-[target.'cfg(all(windows, target_env = "msvc"))'.dependencies]
-libc = { version = "0.2.153", default-features = false }
-
 [target.'cfg(all(not(target_os = "aix"), not(all(windows, target_env = "msvc", not(target_vendor = "uwp")))))'.dependencies]
 object = { version = "0.32.0", default-features = false, optional = true, features = ['read_core', 'elf', 'macho', 'pe', 'unaligned', 'archive'] }
 

library/std/src/lib.rs

@@ -435,6 +435,7 @@ extern crate alloc as alloc_crate;
 // so include it here even if it's unused.
 #[doc(masked)]
 #[allow(unused_extern_crates)]
+#[cfg(not(all(windows, target_env = "msvc")))]
 extern crate libc;
 
 // We always need an unwinder currently for backtraces

library/std/src/os/raw/tests.rs

@@ -1,3 +1,5 @@
+#![cfg(not(all(windows, target_env = "msvc")))]
+
 use crate::any::TypeId;
 
 macro_rules! ok {