Merge pull request #1344 from dtolnay/checkcfg

Resolve unexpected_cfgs warning

build.rs

@@ -1,3 +1,6 @@
+#![allow(unknown_lints)]
+#![allow(unexpected_cfgs)]
+
 use std::env;
 use std::path::{Path, PathBuf};
 use std::process::Command;
@@ -24,6 +27,16 @@ fn main() {
     }
 
     if let Some(rustc) = rustc_version() {
+        if rustc.minor >= 80 {
+            println!("cargo:rustc-check-cfg=cfg(built_with_cargo)");
+            println!("cargo:rustc-check-cfg=cfg(compile_error_if_alloc)");
+            println!("cargo:rustc-check-cfg=cfg(compile_error_if_std)");
+            println!("cargo:rustc-check-cfg=cfg(cxx_experimental_no_alloc)");
+            println!("cargo:rustc-check-cfg=cfg(doc_cfg)");
+            println!("cargo:rustc-check-cfg=cfg(no_core_ffi_c_char)");
+            println!("cargo:rustc-check-cfg=cfg(skip_ui_tests)");
+        }
+
         if rustc.minor < 63 {
             println!("cargo:warning=The cxx crate requires a rustc version 1.63.0 or newer.");
             println!(

tests/ffi/build.rs

@@ -1,3 +1,6 @@
+#![allow(unknown_lints)]
+#![allow(unexpected_cfgs)]
+
 use cxx_build::CFG;
 
 fn main() {

tools/cargo/build.rs

@@ -48,6 +48,9 @@ through crates.io.
 ";
 
 fn main() {
+    println!("cargo:rustc-check-cfg=cfg(feature, values(\"experimental-async-fn\"))");
+    println!("cargo:rustc-check-cfg=cfg(feature, values(\"experimental-enum-variants-from-header\"))");
+
     if Path::new("src/syntax/mod.rs").exists() {
         return;
     }