macros and improvements

main_proc_macro/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "main_proc_macro"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+quote = "1.0.41"
+syn = "2.0.108"

main_proc_macro/src/lib.rs

@@ -0,0 +1,21 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{ItemFn, parse_macro_input};
+
+#[proc_macro_attribute]
+pub fn main(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(item as ItemFn);
+    let name = &input.sig.ident;
+
+    // ensure we emit _start in the same module as the fn
+    let expanded = quote! {
+        #input
+
+        #[unsafe(no_mangle)]
+        pub extern "Rust" fn _start() {
+            #name();
+        }
+    };
+
+    expanded.into()
+}