3 /// Create the `main` function which will initialize the rust runtime and call
4 /// users main function.
5 pub(crate) fn maybe_create_entry_wrapper(
7 module: &mut Module<impl Backend + 'static>,
8 unwind_context: &mut UnwindContext<'_>,
10 use rustc_hir::lang_items::StartFnLangItem;
11 use rustc_session::config::EntryFnType;
13 let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
14 Some((def_id, entry_ty)) => (
17 EntryFnType::Main => true,
18 EntryFnType::Start => false,
24 let instance = Instance::mono(tcx, main_def_id);
25 if module.get_name(&*tcx.symbol_name(instance).name).is_none() {
29 create_entry_fn(tcx, module, unwind_context, main_def_id, use_start_lang_item);
33 m: &mut Module<impl Backend + 'static>,
34 unwind_context: &mut UnwindContext<'_>,
35 rust_main_def_id: DefId,
36 use_start_lang_item: bool,
38 let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
39 // Given that `main()` has no arguments,
40 // then its return type cannot have
41 // late-bound regions, since late-bound
42 // regions must appear in the argument
44 let main_ret_ty = tcx.erase_regions(&main_ret_ty.no_bound_vars().unwrap());
46 let cmain_sig = Signature {
48 AbiParam::new(m.target_config().pointer_type()),
49 AbiParam::new(m.target_config().pointer_type()),
51 returns: vec![AbiParam::new(
52 m.target_config().pointer_type(), /*isize*/
54 call_conv: CallConv::triple_default(m.isa().triple()),
58 .declare_function("main", Linkage::Export, &cmain_sig)
61 let instance = Instance::mono(tcx, rust_main_def_id);
63 let (main_name, main_sig) =
64 get_function_name_and_sig(tcx, m.isa().triple(), instance, false);
66 .declare_function(&main_name, Linkage::Import, &main_sig)
69 let mut ctx = Context::new();
70 ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig.clone());
72 let mut func_ctx = FunctionBuilderContext::new();
73 let mut bcx = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
75 let block = bcx.create_block();
76 bcx.switch_to_block(block);
77 let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
78 let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
80 crate::atomic_shim::init_global_lock(m, &mut bcx);
82 let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
84 let call_inst = if use_start_lang_item {
85 let start_def_id = tcx.require_lang_item(StartFnLangItem, None);
86 let start_instance = Instance::resolve(
88 ParamEnv::reveal_all(),
90 tcx.intern_substs(&[main_ret_ty.into()]),
94 let start_func_id = import_function(tcx, m, start_instance);
98 .func_addr(m.target_config().pointer_type(), main_func_ref);
100 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
101 bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
103 // using user-defined start fn
104 bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
107 let result = bcx.inst_results(call_inst)[0];
108 bcx.ins().return_(&[result]);
109 bcx.seal_all_blocks();
115 &mut cranelift_codegen::binemit::NullTrapSink {},
117 unwind_context.add_function(cmain_func_id, &ctx, m.isa());