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| 1 | +use clippy_utils::diagnostics::span_lint_and_sugg; |
| 2 | +use clippy_utils::in_macro; |
| 3 | +use clippy_utils::paths; |
| 4 | +use clippy_utils::source::snippet_with_macro_callsite; |
| 5 | +use clippy_utils::ty::{is_type_diagnostic_item, is_type_ref_to_diagnostic_item}; |
| 6 | +use if_chain::if_chain; |
| 7 | +use rustc_errors::Applicability; |
| 8 | +use rustc_hir as hir; |
| 9 | +use rustc_lint::{LateContext, LateLintPass}; |
| 10 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 11 | +use rustc_span::symbol::{sym, Symbol}; |
| 12 | + |
| 13 | +declare_clippy_lint! { |
| 14 | + /// **What it does:** Checks for usage of `libc::strlen` on a `CString` or `CStr` value, |
| 15 | + /// and suggest calling `as_bytes().len()` or `to_bytes().len()` respectively instead. |
| 16 | + /// |
| 17 | + /// **Why is this bad?** This avoids calling an unsafe `libc` function. |
| 18 | + /// Currently, it also avoids calculating the length. |
| 19 | + /// |
| 20 | + /// **Known problems:** None. |
| 21 | + /// |
| 22 | + /// **Example:** |
| 23 | + /// |
| 24 | + /// ```rust, ignore |
| 25 | + /// use std::ffi::CString; |
| 26 | + /// let cstring = CString::new("foo").expect("CString::new failed"); |
| 27 | + /// let len = unsafe { libc::strlen(cstring.as_ptr()) }; |
| 28 | + /// ``` |
| 29 | + /// Use instead: |
| 30 | + /// ```rust, no_run |
| 31 | + /// use std::ffi::CString; |
| 32 | + /// let cstring = CString::new("foo").expect("CString::new failed"); |
| 33 | + /// let len = cstring.as_bytes().len(); |
| 34 | + /// ``` |
| 35 | + pub STRLEN_ON_C_STRINGS, |
| 36 | + complexity, |
| 37 | + "using `libc::strlen` on a `CString` or `CStr` value, while `as_bytes().len()` or `to_bytes().len()` respectively can be used instead" |
| 38 | +} |
| 39 | + |
| 40 | +declare_lint_pass!(StrlenOnCStrings => [STRLEN_ON_C_STRINGS]); |
| 41 | + |
| 42 | +impl LateLintPass<'tcx> for StrlenOnCStrings { |
| 43 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) { |
| 44 | + if in_macro(expr.span) { |
| 45 | + return; |
| 46 | + } |
| 47 | + |
| 48 | + if_chain! { |
| 49 | + if let hir::ExprKind::Call(func, [recv]) = expr.kind; |
| 50 | + if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = func.kind; |
| 51 | + |
| 52 | + if (&paths::LIBC_STRLEN).iter().map(|x| Symbol::intern(x)).eq( |
| 53 | + path.segments.iter().map(|seg| seg.ident.name)); |
| 54 | + if let hir::ExprKind::MethodCall(path, _, args, _) = recv.kind; |
| 55 | + if args.len() == 1; |
| 56 | + if !args.iter().any(|e| e.span.from_expansion()); |
| 57 | + if path.ident.name == sym::as_ptr; |
| 58 | + then { |
| 59 | + let cstring = &args[0]; |
| 60 | + let ty = cx.typeck_results().expr_ty(cstring); |
| 61 | + let val_name = snippet_with_macro_callsite(cx, cstring.span, ".."); |
| 62 | + let sugg = if is_type_diagnostic_item(cx, ty, sym::cstring_type){ |
| 63 | + format!("{}.as_bytes().len()", val_name) |
| 64 | + } else if is_type_ref_to_diagnostic_item(cx, ty, sym::CStr){ |
| 65 | + format!("{}.to_bytes().len()", val_name) |
| 66 | + } else { |
| 67 | + return; |
| 68 | + }; |
| 69 | + |
| 70 | + span_lint_and_sugg( |
| 71 | + cx, |
| 72 | + STRLEN_ON_C_STRINGS, |
| 73 | + expr.span, |
| 74 | + "using `libc::strlen` on a `CString` or `CStr` value", |
| 75 | + "try this (you might also need to get rid of `unsafe` block in some cases):", |
| 76 | + sugg, |
| 77 | + Applicability::Unspecified // Sometimes unnecessary `unsafe` block |
| 78 | + ); |
| 79 | + } |
| 80 | + } |
| 81 | + } |
| 82 | +} |
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