Set RUST_MIN_STACK if unset

serde_codegen/src/env.rs

@@ -0,0 +1,36 @@
+use std::env;
+use std::ffi::OsStr;
+use std::ops::Drop;
+
+pub fn set_if_unset<K, V>(k: K, v: V) -> TmpEnv<K>
+    where K: AsRef<OsStr>,
+          V: AsRef<OsStr>,
+{
+    match env::var(&k) {
+        Ok(_) => TmpEnv::WasAlreadySet,
+        Err(_) => {
+            env::set_var(&k, v);
+            TmpEnv::WasNotSet { k: k }
+        }
+    }
+}
+
+#[must_use]
+pub enum TmpEnv<K>
+    where K: AsRef<OsStr>,
+{
+    WasAlreadySet,
+    WasNotSet {
+        k: K,
+    }
+}
+
+impl<K> Drop for TmpEnv<K>
+    where K: AsRef<OsStr>,
+{
+    fn drop(&mut self) {
+        if let TmpEnv::WasNotSet { ref k } = *self {
+            env::remove_var(k);
+        }
+    }
+}