3 /// Create the `main` function which will initialize the rust runtime and call
4 /// users main function.
5 pub fn maybe_create_entry_wrapper<'a, 'tcx: 'a>(
6 tcx: TyCtxt<'a, 'tcx, 'tcx>,
7 module: &mut Module<impl Backend + 'static>,
9 use rustc::middle::lang_items::StartFnLangItem;
10 use rustc::session::config::EntryFnType;
12 let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
13 Some((def_id, entry_ty)) => (
16 EntryFnType::Main => true,
17 EntryFnType::Start => false,
23 create_entry_fn(tcx, module, main_def_id, use_start_lang_item);;
25 fn create_entry_fn<'a, 'tcx: 'a>(
26 tcx: TyCtxt<'a, 'tcx, 'tcx>,
27 m: &mut Module<impl Backend + 'static>,
28 rust_main_def_id: DefId,
29 use_start_lang_item: bool,
31 let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
32 // Given that `main()` has no arguments,
33 // then its return type cannot have
34 // late-bound regions, since late-bound
35 // regions must appear in the argument
37 let main_ret_ty = tcx.erase_regions(&main_ret_ty.no_bound_vars().unwrap());
39 let cmain_sig = Signature {
41 AbiParam::new(m.target_config().pointer_type()),
42 AbiParam::new(m.target_config().pointer_type()),
44 returns: vec![AbiParam::new(
45 m.target_config().pointer_type(), /*isize*/
47 call_conv: CallConv::SystemV,
51 .declare_function("main", Linkage::Export, &cmain_sig)
54 let instance = Instance::mono(tcx, rust_main_def_id);
56 let (main_name, main_sig) = get_function_name_and_sig(tcx, instance);
59 .declare_function(&main_name, Linkage::Import, &main_sig)
62 let mut ctx = Context::new();
63 ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig.clone());
65 let mut func_ctx = FunctionBuilderContext::new();
66 let mut bcx: FunctionBuilder = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
68 let ebb = bcx.create_ebb();
69 bcx.switch_to_block(ebb);
70 let arg_argc = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
71 let arg_argv = bcx.append_ebb_param(ebb, m.target_config().pointer_type());
73 let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
75 let call_inst = if use_start_lang_item {
76 let start_def_id = tcx.require_lang_item(StartFnLangItem);
77 let start_instance = Instance::resolve(
79 ParamEnv::reveal_all(),
81 tcx.intern_substs(&[main_ret_ty.into()]),
84 let start_func_id = import_function(tcx, m, start_instance);
88 .func_addr(m.target_config().pointer_type(), main_func_ref);
90 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
91 bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
93 // using user-defined start fn
94 bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
97 let result = bcx.inst_results(call_inst)[0];
98 bcx.ins().return_(&[result]);
99 bcx.seal_all_blocks();
102 m.define_function(cmain_func_id, &mut ctx).unwrap();