85 lines
3.3 KiB
Rust
85 lines
3.3 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::match_libc_symbol;
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use clippy_utils::source::snippet_with_context;
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use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
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use clippy_utils::visitors::is_expr_unsafe;
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use rustc_errors::Applicability;
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use rustc_hir::{Block, BlockCheckMode, Expr, ExprKind, LangItem, Node, UnsafeSource};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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use rustc_span::symbol::sym;
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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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#[clippy::version = "1.55.0"]
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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<'tcx> LateLintPass<'tcx> for StrlenOnCStrings {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if !expr.span.from_expansion()
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&& let ExprKind::Call(func, [recv]) = expr.kind
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&& let ExprKind::Path(path) = &func.kind
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&& let Some(did) = cx.qpath_res(path, func.hir_id).opt_def_id()
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&& match_libc_symbol(cx, did, "strlen")
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&& let ExprKind::MethodCall(path, self_arg, [], _) = recv.kind
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&& !recv.span.from_expansion()
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&& path.ident.name == sym::as_ptr
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{
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let ctxt = expr.span.ctxt();
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let span = match cx.tcx.parent_hir_node(expr.hir_id) {
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Node::Block(&Block {
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rules: BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided),
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span,
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..
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}) if span.ctxt() == ctxt && !is_expr_unsafe(cx, self_arg) => span,
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_ => expr.span,
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};
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let ty = cx.typeck_results().expr_ty(self_arg).peel_refs();
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let mut app = Applicability::MachineApplicable;
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let val_name = snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0;
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let method_name = if is_type_diagnostic_item(cx, ty, sym::cstring_type) {
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"as_bytes"
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} else if is_type_lang_item(cx, ty, LangItem::CStr) {
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"to_bytes"
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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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span,
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"using `libc::strlen` on a `CString` or `CStr` value",
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"try",
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format!("{val_name}.{method_name}().len()"),
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app,
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);
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}
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}
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}
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