Rollup merge of #40150 - topecongiro:compile-fail-test-cfg-target-has-atomic, r=alexcrichton

Add compile test for cfg_target_has_atomic

Issue #39059.
I am concerned about whether the test is excessive.

src/test/compile-fail/feature-gate-cfg-target-has-atomic.rs

@@ -0,0 +1,86 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type="rlib"]
+#![no_core]
+
+extern "rust-intrinsic" {
+    fn atomic_xadd<T>(dst: *mut T, src: T) -> T;
+}
+
+#[lang = "sized"]
+trait Sized {}
+#[lang = "copy"]
+trait Copy {}
+
+#[cfg(target_has_atomic = "8")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_u8(x: *mut u8) {
+    atomic_xadd(x, 1);
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "8")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_i8(x: *mut i8) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "16")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_u16(x: *mut u16) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "16")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_i16(x: *mut i16) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "32")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_u32(x: *mut u32) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "32")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_i32(x: *mut i32) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "64")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_u64(x: *mut u64) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "64")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_i64(x: *mut i64) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "ptr")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_usize(x: *mut usize) {
+    atomic_xadd(x, 1);
+}
+#[cfg(target_has_atomic = "ptr")]
+//~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+pub unsafe fn atomic_isize(x: *mut isize) {
+    atomic_xadd(x, 1);
+}
+
+fn main() {
+    cfg!(target_has_atomic = "8");
+    //~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+    cfg!(target_has_atomic = "16");
+    //~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+    cfg!(target_has_atomic = "32");
+    //~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+    cfg!(target_has_atomic = "64");
+    //~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+    cfg!(target_has_atomic = "ptr");
+    //~^ ERROR `cfg(target_has_atomic)` is experimental and subject to change (see issue #32976)
+}

src/tools/tidy/src/features.rs

@@ -168,7 +168,6 @@ pub fn check(path: &Path, bad: &mut bool) {
     // FIXME get this whitelist empty.
     let whitelist = vec![
         "abi_ptx", "simd",
-        "cfg_target_has_atomic",
         "stmt_expr_attributes",
         "cfg_target_thread_local", "unwind_attributes",
     ];