Re-export core::ffi::c_void if supported

1 files changed, 35 insertions, 0 deletions

diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000000..aa56ea0545
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,35 @@
+use std::env;
+use std::process::Command;
+use std::str;
+
+fn main() {
+    /*
+     * If `core::ffi::c_void` exists, libc can just re-export it. Otherwise, it
+     * must define an incompatible type to retain backwards-compatibility.
+     */
+    if rustc_minor_version().expect("Failed to get rustc version") >= 31 {
+        println!("cargo:rustc-cfg=core_cvoid");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    macro_rules! otry {
+        ($e:expr) => {
+            match $e {
+                Some(e) => e,
+                None => return None,
+            }
+        };
+    }
+
+    let rustc = otry!(env::var_os("RUSTC"));
+    let output = otry!(Command::new(rustc).arg("--version").output().ok());
+    let version = otry!(str::from_utf8(&output.stdout).ok());
+    let mut pieces = version.split('.');
+
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+
+    otry!(pieces.next()).parse().ok()
+}