support the newest nightly

1 files changed, 8 insertions, 2 deletions

diff --git a/cortex-m-rt/build.rs b/cortex-m-rt/build.rs
index 7784b98..c1028c4 100644
--- a/cortex-m-rt/build.rs
+++ b/cortex-m-rt/build.rs
@@ -10,13 +10,19 @@ use chrono::NaiveDate;
 
 fn main() {
     let meta = rustc_version::version_meta().unwrap();
+    let commit_date = meta.commit_date.unwrap().parse::<NaiveDate>().unwrap();
     if meta.channel == rustc_version::Channel::Dev
-        || meta.commit_date.unwrap().parse::<NaiveDate>().unwrap()
-            > NaiveDate::from_ymd(2017, 12, 26)
+        || commit_date > NaiveDate::from_ymd(2017, 12, 26)
     {
         println!("cargo:rustc-cfg=has_termination_lang")
     }
 
+    // newest nightlies don't need 'extern crate compiler_builtins'
+    if commit_date < NaiveDate::from_ymd(2018, 04, 07)
+    {
+        println!("cargo:rustc-cfg=needs_cb")
+    }
+
     let target = env::var("TARGET").unwrap();
 
     has_fpu(&target);