remove extern c and no_mangle

build.rs

@@ -2,6 +2,8 @@ extern crate cc;
 
 use std::env;
 
+const VERSION: &'static str = env!("CARGO_PKG_VERSION");
+
 fn main() {
     let mut config = cc::Build::new();
     config.file("misc.h");
@@ -31,10 +33,23 @@ fn main() {
     }
 
     let crate_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
-
-    cbindgen::Builder::new()
+    let cfg = cbindgen::Config::from_root_or_default(std::path::Path::new(&crate_dir));
+    let c = cbindgen::Builder::new()
+        .with_config(cfg)
         .with_crate(crate_dir)
-        .generate()
-        .expect("Unable to generate bindings")
-        .write_to_file("deltachat.h");
+        .with_header(format!("/* deltachat Header Version {} */", VERSION))
+        // .with_language(cbindgen::Language::C)
+        .generate();
+
+    // This is needed to ensure we don't panic if there are errors in the crates code
+    // but rather just tell the rest of the system we can't proceed.
+    match c {
+        Ok(res) => {
+            res.write_to_file("deltachat.h");
+        }
+        Err(err) => {
+            eprintln!("unable to generate bindings: {:#?}", err);
+            std::process::exit(1);
+        }
+    }
 }