82 lines
3.2 KiB
Rust
82 lines
3.2 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::in_macro;
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use clippy_utils::paths;
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use clippy_utils::source::snippet_with_macro_callsite;
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use clippy_utils::ty::{is_type_diagnostic_item, is_type_ref_to_diagnostic_item};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir as hir;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::{sym, Symbol};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `libc::strlen` on a `CString` or `CStr` value,
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/// and suggest calling `as_bytes().len()` or `to_bytes().len()` respectively instead.
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///
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/// ### Why is this bad?
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/// This avoids calling an unsafe `libc` function.
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/// Currently, it also avoids calculating the length.
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///
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/// ### Example
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/// ```rust, ignore
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/// use std::ffi::CString;
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/// let cstring = CString::new("foo").expect("CString::new failed");
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/// let len = unsafe { libc::strlen(cstring.as_ptr()) };
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/// ```
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/// Use instead:
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/// ```rust, no_run
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/// use std::ffi::CString;
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/// let cstring = CString::new("foo").expect("CString::new failed");
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/// let len = cstring.as_bytes().len();
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/// ```
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pub STRLEN_ON_C_STRINGS,
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complexity,
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"using `libc::strlen` on a `CString` or `CStr` value, while `as_bytes().len()` or `to_bytes().len()` respectively can be used instead"
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}
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declare_lint_pass!(StrlenOnCStrings => [STRLEN_ON_C_STRINGS]);
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impl LateLintPass<'tcx> for StrlenOnCStrings {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
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if in_macro(expr.span) {
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return;
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}
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if_chain! {
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if let hir::ExprKind::Call(func, [recv]) = expr.kind;
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if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = func.kind;
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if (&paths::LIBC_STRLEN).iter().map(|x| Symbol::intern(x)).eq(
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path.segments.iter().map(|seg| seg.ident.name));
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if let hir::ExprKind::MethodCall(path, _, args, _) = recv.kind;
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if args.len() == 1;
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if !args.iter().any(|e| e.span.from_expansion());
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if path.ident.name == sym::as_ptr;
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then {
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let cstring = &args[0];
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let ty = cx.typeck_results().expr_ty(cstring);
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let val_name = snippet_with_macro_callsite(cx, cstring.span, "..");
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let sugg = if is_type_diagnostic_item(cx, ty, sym::cstring_type){
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format!("{}.as_bytes().len()", val_name)
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} else if is_type_ref_to_diagnostic_item(cx, ty, sym::CStr){
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format!("{}.to_bytes().len()", val_name)
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} else {
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return;
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};
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span_lint_and_sugg(
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cx,
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STRLEN_ON_C_STRINGS,
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expr.span,
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"using `libc::strlen` on a `CString` or `CStr` value",
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"try this (you might also need to get rid of `unsafe` block in some cases):",
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sugg,
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Applicability::Unspecified // Sometimes unnecessary `unsafe` block
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);
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}
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}
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}
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}
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