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//! This module implements the translation of main functions in C.
//! Translating main requires us to wrap the C implementation to
//! a helper that can be called from a generated main function in
//! Rust.
use super::*;
use c2rust_ast_builder::CaptureBy;
use failure::format_err;
use proc_macro2::{TokenStream, TokenTree};
impl<'c> Translation<'c> {
pub fn convert_main(&self, main_id: CDeclId) -> TranslationResult<Box<Item>> {
if let CDeclKind::Function {
ref parameters,
typ,
..
} = self.ast_context.index(main_id).kind
{
let ret: CTypeKind = match self.ast_context.resolve_type(typ).kind {
CTypeKind::Function(ret, _, _, _, _) => {
self.ast_context.resolve_type(ret.ctype).kind.clone()
}
ref k => {
return Err(format_err!(
"Type of main function {:?} was not a function type, got {:?}",
main_id,
k
)
.into())
}
};
let main_fn_name = self
.renamer
.borrow()
.get(&main_id)
.expect("Could not find main function in renamer");
let decl = mk().fn_decl("main", vec![], None, ReturnType::Default);
let main_fn = mk().path_expr(vec![main_fn_name]);
let exit_fn = mk().abs_path_expr(vec!["std", "process", "exit"]);
let args_fn = mk().abs_path_expr(vec!["std", "env", "args"]);
let vars_fn = mk().abs_path_expr(vec!["std", "env", "vars"]);
let no_args: Vec<Box<Expr>> = vec![];
let mut stmts: Vec<Stmt> = vec![];
let mut main_args: Vec<Box<Expr>> = vec![];
let n = parameters.len();
if n >= 2 {
// `argv` and `argc`
stmts.push(mk().local_stmt(Box::new({
// ty = Vec<Vec<u8>>
let ty = mk().path_ty(vec![mk().path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![mk().path_ty(vec![mk()
.path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![mk().ident_ty("u8")]),
)])]),
)]);
// map_arg = |arg| {
// (::std::ffi::CString::new(arg))
// .expect("Failed to convert argument into CString.")
// .into_bytes_with_nul()
// }
let cstring_call = mk().call_expr(
// TODO(kkysen) change `"std"` to `"alloc"` after `#![feature(alloc_c_string)]` is stabilized in `1.63.0`
mk().abs_path_expr(vec!["std", "ffi", "CString", "new"]),
vec![mk().path_expr(vec!["arg"])],
);
let expect_arg = mk().lit_expr("Failed to convert argument into CString.");
let map_arg = mk().closure_expr(
CaptureBy::Ref,
Movability::Movable,
vec![mk().ident_pat("arg")],
ReturnType::Default,
mk().method_chain_expr(
cstring_call,
vec![
(mk().path_segment("expect"), vec![expect_arg]),
(mk().path_segment("into_bytes_with_nul"), vec![]),
],
),
);
// init = args_fn
// .map(map_arg)
// .collect();
let init = mk().method_chain_expr(
mk().call_expr(args_fn, vec![]),
vec![
(mk().path_segment("map"), vec![map_arg]),
(mk().path_segment("collect"), vec![]),
],
);
mk().local(mk().mutbl().ident_pat("args_strings"), Some(ty), Some(init))
})));
stmts.push(mk().local_stmt(Box::new({
// ty = Vec<*mut ::core::ffi::c_char>
let ty = mk().path_ty(vec![mk().path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![mk()
.mutbl()
.ptr_ty(mk().abs_path_ty(vec!["core", "ffi", "c_char"]))]),
)]);
// map_arg = |arg| arg.as_mut_ptr() as *mut ::core::ffi::c_char
let map_arg = mk().closure_expr(
CaptureBy::Ref,
Movability::Movable,
vec![mk().ident_pat("arg")],
ReturnType::Default,
mk().cast_expr(
mk().method_call_expr(mk().ident_expr("arg"), "as_mut_ptr", vec![]),
mk().mutbl()
.ptr_ty(mk().abs_path_ty(vec!["core", "ffi", "c_char"])),
),
);
// chain_arg = ::core::iter::once(::core::ptr::null_mut())
let chain_arg = mk().call_expr(
mk().abs_path_expr(vec!["core", "iter", "once"]),
vec![mk().call_expr(
mk().abs_path_expr(vec!["core", "ptr", "null_mut"]),
vec![],
)],
);
// init = args_strings
// .iter_mut()
// .map(map_arg)
// .chain(chain_arg)
// .collect()
let init = mk().method_chain_expr(
mk().ident_expr("args_strings"),
vec![
(mk().path_segment("iter_mut"), vec![]),
(mk().path_segment("map"), vec![map_arg]),
(mk().path_segment("chain"), vec![chain_arg]),
(mk().path_segment("collect"), vec![]),
],
);
mk().local(mk().mutbl().ident_pat("args_ptrs"), Some(ty), Some(init))
})));
let argc_ty: Box<Type> = match self.ast_context.index(parameters[0]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'argc' argument in main function",
)),
}?;
let argv_ty: Box<Type> = match self.ast_context.index(parameters[1]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'argv' argument in main function",
)),
}?;
let args = mk().ident_expr("args_ptrs");
let argc = mk().binary_expr(
BinOp::Sub(Default::default()),
mk().method_call_expr(args.clone(), "len", no_args.clone()),
mk().lit_expr(mk().int_lit(1, "")),
);
let argv = mk().method_call_expr(args, "as_mut_ptr", no_args.clone());
main_args.push(mk().cast_expr(argc, argc_ty));
main_args.push(mk().cast_expr(argv, argv_ty));
}
if n >= 3 {
// non-standard `envp`
stmts.push(mk().local_stmt(Box::new(mk().local(
mk().mutbl().ident_pat("vars"),
Some(mk().path_ty(vec![mk().path_segment_with_args(
"Vec",
mk().angle_bracketed_args(vec![
mk().mutbl().ptr_ty(mk().abs_path_ty(vec!["core", "ffi", "c_char"])),
]),
)])),
Some(mk().call_expr(mk().path_expr(vec!["Vec", "new"]), vec![])),
))));
let var_name_ident = mk().ident("var_name");
let var_value_ident = mk().ident("var_value");
stmts.push(mk().semi_stmt(mk().for_expr(
mk().tuple_pat(vec![
mk().ident_pat("var_name"),
mk().ident_pat("var_value"),
]),
mk().call_expr(vars_fn, vec![]),
mk().block(vec![
mk().local_stmt(Box::new(
mk().local(
mk().ident_pat("var"),
Some(mk().path_ty(vec!["String"])),
Some(
mk().mac_expr(
mk().mac(
mk().path(vec!["format"]),
vec![
TokenTree::Literal(
proc_macro2::Literal::string("{}={}"),
),
TokenTree::Punct(Punct::new(
',',
proc_macro2::Spacing::Alone,
)),
TokenTree::Ident(var_name_ident),
TokenTree::Punct(Punct::new(
',',
proc_macro2::Spacing::Alone,
)),
TokenTree::Ident(var_value_ident),
]
.into_iter()
.collect::<TokenStream>(),
MacroDelimiter::Paren(Default::default()),
),
),
),
),
)),
mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["vars"]),
"push",
vec![mk().method_call_expr(
mk().method_call_expr(
mk().call_expr(
mk().abs_path_expr(vec![
// TODO(kkysen) change `"std"` to `"alloc"` after `#![feature(alloc_c_string)]` is stabilized in `1.63.0`
"std", "ffi", "CString", "new",
]),
vec![mk().path_expr(vec!["var"])],
),
"expect",
vec![mk().lit_expr(
"Failed to convert environment variable into CString."
)],
),
"into_raw",
vec![],
)],
)),
]),
None as Option<Ident>,
)));
stmts.push(mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["vars"]),
"push",
vec![
mk().call_expr(mk().abs_path_expr(vec!["core", "ptr", "null_mut"]), vec![]),
],
)));
let envp_ty: Box<Type> = match self.ast_context.index(parameters[2]).kind {
CDeclKind::Variable { ref typ, .. } => self.convert_type(typ.ctype),
_ => Err(TranslationError::generic(
"Cannot find type of 'envp' argument in main function",
)),
}?;
let envp = mk().method_call_expr(mk().ident_expr("vars"), "as_mut_ptr", no_args);
main_args.push(mk().cast_expr(envp, envp_ty));
}
// Check `main` has the right form
if n != 0 && n != 2 && n != 3 {
return Err(format_err!(
"Main function should have 0, 2, or 3 parameters, not {}.",
n
)
.into());
};
if let CTypeKind::Void = ret {
let call_main = mk().call_expr(main_fn, main_args);
let unsafe_block = mk().unsafe_block(vec![mk().expr_stmt(call_main)]);
stmts.push(mk().expr_stmt(mk().unsafe_block_expr(unsafe_block)));
let exit_arg = mk().lit_expr(mk().int_lit(0, "i32"));
let call_exit = mk().call_expr(exit_fn, vec![exit_arg]);
stmts.push(mk().semi_stmt(call_exit));
} else {
let call_main = mk().cast_expr(
mk().call_expr(main_fn, main_args),
mk().path_ty(vec!["i32"]),
);
let call_exit = mk().call_expr(exit_fn, vec![call_main]);
let unsafe_block = mk().unsafe_block(vec![mk().expr_stmt(call_exit)]);
stmts.push(mk().expr_stmt(mk().unsafe_block_expr(unsafe_block)));
};
let block = mk().block(stmts);
let main_attributes = self.mk_cross_check(mk(), vec!["none"]);
Ok(main_attributes.pub_().fn_item(decl, block))
} else {
Err(TranslationError::generic(
"Cannot translate non-function main entry point",
))
}
}
}