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Auto merge of #11919 - y21:manual_c_str_literals, r=xFrednet
new lint: `manual_c_str_literals` With rust-lang/rust#117472 merged and `c""` syntax stabilized, I think it'd be nice to have a lint for using `CStr::from_ptr` (and similar constructors) with a string literal as an argument. We can probably also lint `"foo\0".as_ptr()` and suggest `c"foo".as_ptr()`. I might add that to this PR tomorrow if I find the time. The byte string literal to c string literal rewriting is ugly but oh well. changelog: new lint: `manual_c_str_literals` [#11919](#11919)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,197 @@ | ||
| use clippy_config::msrvs::{self, Msrv}; | ||
| use clippy_utils::diagnostics::span_lint_and_sugg; | ||
| use clippy_utils::get_parent_expr; | ||
| use clippy_utils::source::snippet; | ||
| use rustc_ast::{LitKind, StrStyle}; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{Expr, ExprKind, Node, QPath, TyKind}; | ||
| use rustc_lint::LateContext; | ||
| use rustc_span::{sym, Span, Symbol}; | ||
|
|
||
| use super::MANUAL_C_STR_LITERALS; | ||
|
|
||
| /// Checks: | ||
| /// - `b"...".as_ptr()` | ||
| /// - `b"...".as_ptr().cast()` | ||
| /// - `"...".as_ptr()` | ||
| /// - `"...".as_ptr().cast()` | ||
| /// | ||
| /// Iff the parent call of `.cast()` isn't `CStr::from_ptr`, to avoid linting twice. | ||
| pub(super) fn check_as_ptr<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| expr: &'tcx Expr<'tcx>, | ||
| receiver: &'tcx Expr<'tcx>, | ||
| msrv: &Msrv, | ||
| ) { | ||
| if let ExprKind::Lit(lit) = receiver.kind | ||
| && let LitKind::ByteStr(_, StrStyle::Cooked) | LitKind::Str(_, StrStyle::Cooked) = lit.node | ||
| && let casts_removed = peel_ptr_cast_ancestors(cx, expr) | ||
| && !get_parent_expr(cx, casts_removed).is_some_and( | ||
| |parent| matches!(parent.kind, ExprKind::Call(func, _) if is_c_str_function(cx, func).is_some()), | ||
| ) | ||
| && let Some(sugg) = rewrite_as_cstr(cx, lit.span) | ||
| && msrv.meets(msrvs::C_STR_LITERALS) | ||
| { | ||
| span_lint_and_sugg( | ||
| cx, | ||
| MANUAL_C_STR_LITERALS, | ||
| receiver.span, | ||
| "manually constructing a nul-terminated string", | ||
| r#"use a `c""` literal"#, | ||
| sugg, | ||
| // an additional cast may be needed, since the type of `CStr::as_ptr` and | ||
| // `"".as_ptr()` can differ and is platform dependent | ||
| Applicability::HasPlaceholders, | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| /// Checks if the callee is a "relevant" `CStr` function considered by this lint. | ||
| /// Returns the function name. | ||
| fn is_c_str_function(cx: &LateContext<'_>, func: &Expr<'_>) -> Option<Symbol> { | ||
| if let ExprKind::Path(QPath::TypeRelative(cstr, fn_name)) = &func.kind | ||
| && let TyKind::Path(QPath::Resolved(_, ty_path)) = &cstr.kind | ||
| && cx.tcx.lang_items().c_str() == ty_path.res.opt_def_id() | ||
| { | ||
| Some(fn_name.ident.name) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| /// Checks calls to the `CStr` constructor functions: | ||
| /// - `CStr::from_bytes_with_nul(..)` | ||
| /// - `CStr::from_bytes_with_nul_unchecked(..)` | ||
| /// - `CStr::from_ptr(..)` | ||
| pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, func: &Expr<'_>, args: &[Expr<'_>], msrv: &Msrv) { | ||
| if let Some(fn_name) = is_c_str_function(cx, func) | ||
| && let [arg] = args | ||
| && msrv.meets(msrvs::C_STR_LITERALS) | ||
| { | ||
| match fn_name.as_str() { | ||
| name @ ("from_bytes_with_nul" | "from_bytes_with_nul_unchecked") | ||
| if !arg.span.from_expansion() | ||
| && let ExprKind::Lit(lit) = arg.kind | ||
| && let LitKind::ByteStr(_, StrStyle::Cooked) | LitKind::Str(_, StrStyle::Cooked) = lit.node => | ||
| { | ||
| check_from_bytes(cx, expr, arg, name); | ||
| }, | ||
| "from_ptr" => check_from_ptr(cx, expr, arg), | ||
| _ => {}, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Checks `CStr::from_ptr(b"foo\0".as_ptr().cast())` | ||
| fn check_from_ptr(cx: &LateContext<'_>, expr: &Expr<'_>, arg: &Expr<'_>) { | ||
| if let ExprKind::MethodCall(method, lit, ..) = peel_ptr_cast(arg).kind | ||
| && method.ident.name == sym::as_ptr | ||
| && !lit.span.from_expansion() | ||
| && let ExprKind::Lit(lit) = lit.kind | ||
| && let LitKind::ByteStr(_, StrStyle::Cooked) = lit.node | ||
| && let Some(sugg) = rewrite_as_cstr(cx, lit.span) | ||
| { | ||
| span_lint_and_sugg( | ||
| cx, | ||
| MANUAL_C_STR_LITERALS, | ||
| expr.span, | ||
| "calling `CStr::from_ptr` with a byte string literal", | ||
| r#"use a `c""` literal"#, | ||
| sugg, | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| } | ||
| /// Checks `CStr::from_bytes_with_nul(b"foo\0")` | ||
| fn check_from_bytes(cx: &LateContext<'_>, expr: &Expr<'_>, arg: &Expr<'_>, method: &str) { | ||
| let (span, applicability) = if let Some(parent) = get_parent_expr(cx, expr) | ||
| && let ExprKind::MethodCall(method, ..) = parent.kind | ||
| && [sym::unwrap, sym::expect].contains(&method.ident.name) | ||
| { | ||
| (parent.span, Applicability::MachineApplicable) | ||
| } else if method == "from_bytes_with_nul_unchecked" { | ||
| // `*_unchecked` returns `&CStr` directly, nothing needs to be changed | ||
| (expr.span, Applicability::MachineApplicable) | ||
| } else { | ||
| // User needs to remove error handling, can't be machine applicable | ||
| (expr.span, Applicability::HasPlaceholders) | ||
| }; | ||
|
|
||
| let Some(sugg) = rewrite_as_cstr(cx, arg.span) else { | ||
| return; | ||
| }; | ||
|
|
||
| span_lint_and_sugg( | ||
| cx, | ||
| MANUAL_C_STR_LITERALS, | ||
| span, | ||
| "calling `CStr::new` with a byte string literal", | ||
| r#"use a `c""` literal"#, | ||
| sugg, | ||
| applicability, | ||
| ); | ||
| } | ||
|
|
||
| /// Rewrites a byte string literal to a c-str literal. | ||
| /// `b"foo\0"` -> `c"foo"` | ||
| /// | ||
| /// Returns `None` if it doesn't end in a NUL byte. | ||
| fn rewrite_as_cstr(cx: &LateContext<'_>, span: Span) -> Option<String> { | ||
| let mut sugg = String::from("c") + snippet(cx, span.source_callsite(), "..").trim_start_matches('b'); | ||
|
|
||
| // NUL byte should always be right before the closing quote. | ||
| if let Some(quote_pos) = sugg.rfind('"') { | ||
| // Possible values right before the quote: | ||
| // - literal NUL value | ||
| if sugg.as_bytes()[quote_pos - 1] == b'\0' { | ||
| sugg.remove(quote_pos - 1); | ||
| } | ||
| // - \x00 | ||
| else if sugg[..quote_pos].ends_with("\\x00") { | ||
| sugg.replace_range(quote_pos - 4..quote_pos, ""); | ||
| } | ||
| // - \0 | ||
| else if sugg[..quote_pos].ends_with("\\0") { | ||
| sugg.replace_range(quote_pos - 2..quote_pos, ""); | ||
| } | ||
| // No known suffix, so assume it's not a C-string. | ||
| else { | ||
| return None; | ||
| } | ||
| } | ||
|
|
||
| Some(sugg) | ||
| } | ||
|
|
||
| fn get_cast_target<'tcx>(e: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> { | ||
| match &e.kind { | ||
| ExprKind::MethodCall(method, receiver, [], _) if method.ident.as_str() == "cast" => Some(receiver), | ||
| ExprKind::Cast(expr, _) => Some(expr), | ||
| _ => None, | ||
| } | ||
| } | ||
|
|
||
| /// `x.cast()` -> `x` | ||
| /// `x as *const _` -> `x` | ||
| /// `x` -> `x` (returns the same expression for non-cast exprs) | ||
| fn peel_ptr_cast<'tcx>(e: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> { | ||
| get_cast_target(e).map_or(e, peel_ptr_cast) | ||
| } | ||
|
|
||
| /// Same as `peel_ptr_cast`, but the other way around, by walking up the ancestor cast expressions: | ||
| /// | ||
| /// `foo(x.cast() as *const _)` | ||
| /// ^ given this `x` expression, returns the `foo(...)` expression | ||
| fn peel_ptr_cast_ancestors<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> { | ||
| let mut prev = e; | ||
| for (_, node) in cx.tcx.hir().parent_iter(e.hir_id) { | ||
| if let Node::Expr(e) = node | ||
| && get_cast_target(e).is_some() | ||
| { | ||
| prev = e; | ||
| } else { | ||
| break; | ||
| } | ||
| } | ||
| prev | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,60 @@ | ||
| #![warn(clippy::manual_c_str_literals)] | ||
| #![allow(clippy::no_effect)] | ||
|
|
||
| use std::ffi::CStr; | ||
|
|
||
| macro_rules! cstr { | ||
| ($s:literal) => { | ||
| CStr::from_bytes_with_nul(concat!($s, "\0").as_bytes()).unwrap() | ||
| }; | ||
| } | ||
|
|
||
| macro_rules! macro_returns_c_str { | ||
| () => { | ||
| CStr::from_bytes_with_nul(b"foo\0").unwrap(); | ||
| }; | ||
| } | ||
|
|
||
| macro_rules! macro_returns_byte_string { | ||
| () => { | ||
| b"foo\0" | ||
| }; | ||
| } | ||
|
|
||
| #[clippy::msrv = "1.76.0"] | ||
| fn pre_stabilization() { | ||
| CStr::from_bytes_with_nul(b"foo\0"); | ||
| } | ||
|
|
||
| #[clippy::msrv = "1.77.0"] | ||
| fn post_stabilization() { | ||
| c"foo"; | ||
| } | ||
|
|
||
| fn main() { | ||
| c"foo"; | ||
| c"foo"; | ||
| c"foo"; | ||
| c"foo\\0sdsd"; | ||
| CStr::from_bytes_with_nul(br"foo\\0sdsd\0").unwrap(); | ||
| CStr::from_bytes_with_nul(br"foo\x00").unwrap(); | ||
| CStr::from_bytes_with_nul(br##"foo#a\0"##).unwrap(); | ||
|
|
||
| unsafe { c"foo" }; | ||
| unsafe { c"foo" }; | ||
| let _: *const _ = c"foo".as_ptr(); | ||
| let _: *const _ = c"foo".as_ptr(); | ||
| let _: *const _ = "foo".as_ptr(); // not a C-string | ||
| let _: *const _ = "".as_ptr(); | ||
| let _: *const _ = c"foo".as_ptr().cast::<i8>(); | ||
| let _ = "电脑".as_ptr(); | ||
| let _ = "电脑\\".as_ptr(); | ||
| let _ = c"电脑\\".as_ptr(); | ||
| let _ = c"电脑".as_ptr(); | ||
| let _ = c"电脑".as_ptr(); | ||
|
|
||
| // Macro cases, don't lint: | ||
| cstr!("foo"); | ||
| macro_returns_c_str!(); | ||
| CStr::from_bytes_with_nul(macro_returns_byte_string!()).unwrap(); | ||
| } |
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