1 use clippy_utils::diagnostics::span_lint_and_then;
2 use rustc_ast::ast::{Expr, ExprKind};
3 use rustc_ast::token::{Lit, LitKind};
4 use rustc_errors::Applicability;
5 use rustc_lint::{EarlyContext, EarlyLintPass};
6 use rustc_middle::lint::in_external_macro;
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 declare_clippy_lint! {
13 /// Checks for `\0` escapes in string and byte literals that look like octal
14 /// character escapes in C.
16 /// ### Why is this bad?
18 /// C and other languages support octal character escapes in strings, where
19 /// a backslash is followed by up to three octal digits. For example, `\033`
20 /// stands for the ASCII character 27 (ESC). Rust does not support this
21 /// notation, but has the escape code `\0` which stands for a null
22 /// byte/character, and any following digits do not form part of the escape
23 /// sequence. Therefore, `\033` is not a compiler error but the result may
26 /// ### Known problems
27 /// The actual meaning can be the intended one. `\x00` can be used in these
28 /// cases to be unambigious.
30 /// The lint does not trigger for format strings in `print!()`, `write!()`
31 /// and friends since the string is already preprocessed when Clippy lints
37 /// let one = "\033[1m Bold? \033[0m"; // \033 intended as escape
38 /// let two = "\033\0"; // \033 intended as null-3-3
41 /// let one = "\x1b[1mWill this be bold?\x1b[0m";
42 /// let two = "\x0033\x00";
44 #[clippy::version = "1.58.0"]
47 "string escape sequences looking like octal characters"
50 declare_lint_pass!(OctalEscapes => [OCTAL_ESCAPES]);
52 impl EarlyLintPass for OctalEscapes {
53 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
54 if in_external_macro(cx.sess, expr.span) {
58 if let ExprKind::Lit(lit) = &expr.kind {
59 if matches!(lit.token.kind, LitKind::Str) {
60 check_lit(cx, &lit.token, lit.span, true);
61 } else if matches!(lit.token.kind, LitKind::ByteStr) {
62 check_lit(cx, &lit.token, lit.span, false);
68 fn check_lit(cx: &EarlyContext<'_>, lit: &Lit, span: Span, is_string: bool) {
69 let contents = lit.symbol.as_str();
70 let mut iter = contents.char_indices().peekable();
71 let mut found = vec![];
73 // go through the string, looking for \0[0-7][0-7]?
74 while let Some((from, ch)) = iter.next() {
76 if let Some((_, '0')) = iter.next() {
77 // collect up to two further octal digits
78 if let Some((mut to, '0'..='7')) = iter.next() {
79 if let Some((_, '0'..='7')) = iter.peek() {
82 found.push((from, to + 1));
92 // construct two suggestion strings, one with \x escapes with octal meaning
93 // as in C, and one with \x00 for null bytes.
94 let mut suggest_1 = if is_string { "\"" } else { "b\"" }.to_string();
95 let mut suggest_2 = suggest_1.clone();
97 for (from, to) in found {
98 suggest_1.push_str(&contents[index..from]);
99 suggest_2.push_str(&contents[index..from]);
101 // construct a replacement escape
102 // the maximum value is \077, or \x3f, so u8 is sufficient here
103 if let Ok(n) = u8::from_str_radix(&contents[from + 1..to], 8) {
104 write!(&mut suggest_1, "\\x{:02x}", n).unwrap();
107 // append the null byte as \x00 and the following digits literally
108 suggest_2.push_str("\\x00");
109 suggest_2.push_str(&contents[from + 2..to]);
113 suggest_1.push_str(&contents[index..]);
115 suggest_2.push_str(&contents[index..]);
123 "octal-looking escape in {} literal",
124 if is_string { "string" } else { "byte string" }
128 "octal escapes are not supported, `\\0` is always a null {}",
129 if is_string { "character" } else { "byte" }
131 // suggestion 1: equivalent hex escape
132 diag.span_suggestion(
134 "if an octal escape was intended, use the hexadecimal representation instead",
136 Applicability::MaybeIncorrect,
138 // suggestion 2: unambiguous null byte
139 diag.span_suggestion(
142 "if the null {} is intended, disambiguate using",
143 if is_string { "character" } else { "byte" }
146 Applicability::MaybeIncorrect,