3 /// Create the `main` function which will initialize the rust runtime and call
4 /// users main function.
5 pub fn maybe_create_entry_wrapper(tcx: TyCtxt<'_>, module: &mut Module<impl Backend + 'static>) {
6 use rustc::middle::lang_items::StartFnLangItem;
7 use rustc::session::config::EntryFnType;
9 let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
10 Some((def_id, entry_ty)) => (
13 EntryFnType::Main => true,
14 EntryFnType::Start => false,
20 create_entry_fn(tcx, module, main_def_id, use_start_lang_item);
24 m: &mut Module<impl Backend + 'static>,
25 rust_main_def_id: DefId,
26 use_start_lang_item: bool,
28 let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
29 // Given that `main()` has no arguments,
30 // then its return type cannot have
31 // late-bound regions, since late-bound
32 // regions must appear in the argument
34 let main_ret_ty = tcx.erase_regions(&main_ret_ty.no_bound_vars().unwrap());
36 let cmain_sig = Signature {
38 AbiParam::new(m.target_config().pointer_type()),
39 AbiParam::new(m.target_config().pointer_type()),
41 returns: vec![AbiParam::new(
42 m.target_config().pointer_type(), /*isize*/
44 call_conv: crate::default_call_conv(tcx.sess),
48 .declare_function("main", Linkage::Export, &cmain_sig)
51 let instance = Instance::mono(tcx, rust_main_def_id);
53 let (main_name, main_sig) = get_function_name_and_sig(tcx, instance, false);
55 .declare_function(&main_name, Linkage::Import, &main_sig)
58 let mut ctx = Context::new();
59 ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig.clone());
61 let mut func_ctx = FunctionBuilderContext::new();
62 let mut bcx: FunctionBuilder = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
64 let ebb = bcx.create_ebb();
65 bcx.switch_to_block(ebb);
66 let arg_argc = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
67 let arg_argv = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
69 let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
71 let call_inst = if use_start_lang_item {
72 let start_def_id = tcx.require_lang_item(StartFnLangItem, None);
73 let start_instance = Instance::resolve(
75 ParamEnv::reveal_all(),
77 tcx.intern_substs(&[main_ret_ty.into()]),
80 let start_func_id = import_function(tcx, m, start_instance);
84 .func_addr(m.target_config().pointer_type(), main_func_ref);
86 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
87 bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
89 // using user-defined start fn
90 bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
93 let result = bcx.inst_results(call_inst)[0];
94 bcx.ins().return_(&[result]);
95 bcx.seal_all_blocks();
98 m.define_function(cmain_func_id, &mut ctx).unwrap();