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Merged
kkysen merged 4 commits into from
Dec 7, 2025
Merged

transpile: Do not leak main argument strings #1447

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3d69d36
ast-builder: Fix/improve handling of closure expressions
Rua Nov 7, 2025
2a91da8
ast-builder: Add `method_chain_expr` convenience function
Rua Nov 8, 2025
e686f1e
transpile: Add snapshot test for main function
Rua Nov 12, 2025
2d546aa
transpile: Do not leak `main` argument strings
Rua Dec 7, 2025
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23 changes: 14 additions & 9 deletions c2rust-ast-builder/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -664,6 +664,17 @@ impl Builder {
)))
}

/// A convenience function for calling multiple methods in a chain.
pub fn method_chain_expr(
self,
expr: Box<Expr>,
calls: Vec<(PathSegment, Vec<Box<Expr>>)>,
) -> Box<Expr> {
calls.into_iter().fold(expr, |expr, (seg, args)| {
mk().method_call_expr(expr, seg, args)
})
}

pub fn tuple_expr(self, exprs: Vec<Box<Expr>>) -> Box<Expr> {
Box::new(Expr::Tuple(ExprTuple {
attrs: self.attrs,
Expand Down Expand Up @@ -2088,17 +2099,11 @@ impl Builder {
self,
capture: CaptureBy,
mov: Movability,
decl: FnDecl,
inputs: Vec<Pat>,
output: ReturnType,
body: Box<Expr>,
) -> Box<Expr> {
let (_name, inputs, _variadic, output) = decl;
let inputs = inputs
.into_iter()
.map(|e| match e {
FnArg::Receiver(_s) => panic!("found 'self' in closure arguments"),
FnArg::Typed(PatType { pat, .. }) => *pat,
})
.collect();
let inputs = inputs.into_iter().collect();
let capture = match capture {
CaptureBy::Ref => None,
CaptureBy::Value => Some(Default::default()),
Expand Down
2 changes: 1 addition & 1 deletion c2rust-ast-builder/src/lib.rs
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Original file line number Diff line number Diff line change
@@ -1,2 +1,2 @@
mod builder;
pub use crate::builder::{mk, properties, Builder, Make};
pub use crate::builder::{mk, properties, Builder, CaptureBy, Make};
128 changes: 90 additions & 38 deletions c2rust-transpile/src/translator/main_function.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
//! Rust.

use super::*;
use c2rust_ast_builder::CaptureBy;
use failure::format_err;
use proc_macro2::{TokenStream, TokenTree};

Expand Down Expand Up @@ -53,45 +54,97 @@ impl<'c> Translation<'c> {
if n >= 2 {
// `argv` and `argc`

stmts.push(mk().local_stmt(Box::new(mk().local(
mk().mutbl().ident_pat("args"),
Some(mk().path_ty(vec![mk().path_segment_with_args(
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().mutbl().ptr_ty(mk().abs_path_ty(vec!["core", "ffi", "c_char"])),
]),
)])),
Some(mk().call_expr(mk().path_expr(vec!["Vec", "new"]), vec![])),
))));
stmts.push(mk().semi_stmt(mk().for_expr(
mk().ident_pat("arg"),
mk().call_expr(args_fn, vec![]),
mk().block(vec![mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["args"]),
"push",
vec![mk().method_call_expr(
mk().method_call_expr(
mk().call_expr(
// TODO(kkysen) change `"std"` to `"alloc"` after `#![feature(alloc_c_string)]` is stabilized in `1.63.0`
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@kkysen kkysen Dec 7, 2025

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Can you keep this comment?

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@kkysen kkysen Dec 7, 2025

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Actually, I think we can switch to it now. rust-lang/rust#99277 was merged on 2022-07-16, before 2022-08-08.

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@Rua Rua Dec 7, 2025 •
edited
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Changing std to alloc doesn't seem to work:

failed to resolve: use of unresolved module or unlinked crate alloc

I guess that it's not as simple as just swapping out one for the other.

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@kkysen kkysen Dec 7, 2025

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Ah, I think we also need to add extern crate alloc;. We can do that separately then, and just leave the comment here for now.

mk().abs_path_expr(vec!["std", "ffi", "CString", "new"]),
vec![mk().path_expr(vec!["arg"])],
),
"expect",
vec![mk().lit_expr("Failed to convert argument into CString.")],
),
"into_raw",
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![],
)],
))]),
None::<Ident>,
)));
stmts.push(mk().semi_stmt(mk().method_call_expr(
mk().path_expr(vec!["args"]),
"push",
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),
Expand All @@ -105,8 +158,7 @@ impl<'c> Translation<'c> {
"Cannot find type of 'argv' argument in main function",
)),
}?;

let args = mk().ident_expr("args");
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()),
Expand Down
3 changes: 3 additions & 0 deletions c2rust-transpile/tests/snapshots/main.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
int main(int argc, char **argv, char **envp) {
return 0;
}
51 changes: 51 additions & 0 deletions c2rust-transpile/tests/snapshots/[email protected]
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Original file line number Diff line number Diff line change
@@ -0,0 +1,51 @@
---
source: c2rust-transpile/tests/snapshots.rs
expression: cat tests/snapshots/main.rs
input_file: c2rust-transpile/tests/snapshots/main.c
---
#![allow(
dead_code,
non_camel_case_types,
non_snake_case,
non_upper_case_globals,
unused_assignments,
unused_mut
)]
unsafe fn main_0(
mut argc: ::core::ffi::c_int,
mut argv: *mut *mut ::core::ffi::c_char,
mut envp: *mut *mut ::core::ffi::c_char,
) -> ::core::ffi::c_int {
return 0 as ::core::ffi::c_int;
}
pub fn main() {
let mut args_strings: Vec<Vec<u8>> = ::std::env::args()
.map(|arg| {
::std::ffi::CString::new(arg)
.expect("Failed to convert argument into CString.")
.into_bytes_with_nul()
})
.collect();
let mut args_ptrs: Vec<*mut ::core::ffi::c_char> = args_strings
.iter_mut()
.map(|arg| arg.as_mut_ptr() as *mut ::core::ffi::c_char)
.chain(::core::iter::once(::core::ptr::null_mut()))
.collect();
let mut vars: Vec<*mut ::core::ffi::c_char> = Vec::new();
for (var_name, var_value) in ::std::env::vars() {
let var: String = format!("{}={}", var_name, var_value);
vars.push(
::std::ffi::CString::new(var)
.expect("Failed to convert environment variable into CString.")
.into_raw(),
);
}
vars.push(::core::ptr::null_mut());
unsafe {
::std::process::exit(main_0(
(args_ptrs.len() - 1) as ::core::ffi::c_int,
args_ptrs.as_mut_ptr() as *mut *mut ::core::ffi::c_char,
vars.as_mut_ptr() as *mut *mut ::core::ffi::c_char,
) as i32)
}
}