1 use cranelift_codegen::binemit::{NullStackMapSink, NullTrapSink};
2 use rustc_hir::LangItem;
3 use rustc_session::config::EntryFnType;
7 /// Create the `main` function which will initialize the rust runtime and call
8 /// users main function.
9 pub(crate) fn maybe_create_entry_wrapper(
11 module: &mut impl Module,
12 unwind_context: &mut UnwindContext<'_>,
14 let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
15 Some((def_id, entry_ty)) => (
18 EntryFnType::Main => true,
19 EntryFnType::Start => false,
25 let instance = Instance::mono(tcx, main_def_id).polymorphize(tcx);
26 if module.get_name(&*tcx.symbol_name(instance).name).is_none() {
30 create_entry_fn(tcx, module, unwind_context, main_def_id, use_start_lang_item);
35 unwind_context: &mut UnwindContext<'_>,
36 rust_main_def_id: DefId,
37 use_start_lang_item: bool,
39 let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
40 // Given that `main()` has no arguments,
41 // then its return type cannot have
42 // late-bound regions, since late-bound
43 // regions must appear in the argument
45 let main_ret_ty = tcx.erase_regions(main_ret_ty.no_bound_vars().unwrap());
47 let cmain_sig = Signature {
49 AbiParam::new(m.target_config().pointer_type()),
50 AbiParam::new(m.target_config().pointer_type()),
52 returns: vec![AbiParam::new(m.target_config().pointer_type() /*isize*/)],
53 call_conv: CallConv::triple_default(m.isa().triple()),
56 let cmain_func_id = m.declare_function("main", Linkage::Export, &cmain_sig).unwrap();
58 let instance = Instance::mono(tcx, rust_main_def_id).polymorphize(tcx);
60 let main_name = tcx.symbol_name(instance).name.to_string();
61 let main_sig = get_function_sig(tcx, m.isa().triple(), instance);
62 let main_func_id = m.declare_function(&main_name, Linkage::Import, &main_sig).unwrap();
64 let mut ctx = Context::new();
65 ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig);
67 let mut func_ctx = FunctionBuilderContext::new();
68 let mut bcx = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
70 let block = bcx.create_block();
71 bcx.switch_to_block(block);
72 let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
73 let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
75 let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
77 let call_inst = if use_start_lang_item {
78 let start_def_id = tcx.require_lang_item(LangItem::Start, None);
79 let start_instance = Instance::resolve(
81 ParamEnv::reveal_all(),
83 tcx.intern_substs(&[main_ret_ty.into()]),
88 let start_func_id = import_function(tcx, m, start_instance);
90 let main_val = bcx.ins().func_addr(m.target_config().pointer_type(), main_func_ref);
92 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
93 bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
95 // using user-defined start fn
96 bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
99 let result = bcx.inst_results(call_inst)[0];
100 bcx.ins().return_(&[result]);
101 bcx.seal_all_blocks();
104 m.define_function(cmain_func_id, &mut ctx, &mut NullTrapSink {}, &mut NullStackMapSink {})
106 unwind_context.add_function(cmain_func_id, &ctx, m.isa());