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Add new lint: strlen_on_c_strings
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@ -2798,6 +2798,7 @@ Released 2018-09-13
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[`string_from_utf8_as_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_from_utf8_as_bytes
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[`string_lit_as_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_lit_as_bytes
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[`string_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#string_to_string
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[`strlen_on_c_strings`]: https://rust-lang.github.io/rust-clippy/master/index.html#strlen_on_c_strings
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[`struct_excessive_bools`]: https://rust-lang.github.io/rust-clippy/master/index.html#struct_excessive_bools
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[`suboptimal_flops`]: https://rust-lang.github.io/rust-clippy/master/index.html#suboptimal_flops
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[`suspicious_arithmetic_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_arithmetic_impl
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@ -338,6 +338,7 @@ mod size_of_in_element_count;
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mod slow_vector_initialization;
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mod stable_sort_primitive;
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mod strings;
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mod strlen_on_c_strings;
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mod suspicious_operation_groupings;
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mod suspicious_trait_impl;
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mod swap;
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@ -914,6 +915,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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strings::STRING_LIT_AS_BYTES,
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strings::STRING_TO_STRING,
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strings::STR_TO_STRING,
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strlen_on_c_strings::STRLEN_ON_C_STRINGS,
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suspicious_operation_groupings::SUSPICIOUS_OPERATION_GROUPINGS,
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suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL,
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suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
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@ -1410,6 +1412,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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LintId::of(slow_vector_initialization::SLOW_VECTOR_INITIALIZATION),
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LintId::of(stable_sort_primitive::STABLE_SORT_PRIMITIVE),
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LintId::of(strings::STRING_FROM_UTF8_AS_BYTES),
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LintId::of(strlen_on_c_strings::STRLEN_ON_C_STRINGS),
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LintId::of(suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL),
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LintId::of(suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL),
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LintId::of(swap::ALMOST_SWAPPED),
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@ -1639,6 +1642,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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LintId::of(reference::REF_IN_DEREF),
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LintId::of(repeat_once::REPEAT_ONCE),
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LintId::of(strings::STRING_FROM_UTF8_AS_BYTES),
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LintId::of(strlen_on_c_strings::STRLEN_ON_C_STRINGS),
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LintId::of(swap::MANUAL_SWAP),
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LintId::of(temporary_assignment::TEMPORARY_ASSIGNMENT),
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LintId::of(transmute::CROSSPOINTER_TRANSMUTE),
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@ -2096,6 +2100,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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store.register_late_pass(move || box missing_enforced_import_rename::ImportRename::new(import_renames.clone()));
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let scripts = conf.allowed_scripts.clone();
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store.register_early_pass(move || box disallowed_script_idents::DisallowedScriptIdents::new(&scripts));
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store.register_late_pass(|| box strlen_on_c_strings::StrlenOnCStrings);
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}
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#[rustfmt::skip]
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82
clippy_lints/src/strlen_on_c_strings.rs
Normal file
82
clippy_lints/src/strlen_on_c_strings.rs
Normal file
@ -0,0 +1,82 @@
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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:** 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?** 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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/// **Known problems:** None.
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///
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/// **Example:**
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///
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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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@ -82,6 +82,7 @@ pub const ITER_REPEAT: [&str; 5] = ["core", "iter", "sources", "repeat", "repeat
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pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
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#[cfg(feature = "internal-lints")]
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pub const LATE_CONTEXT: [&str; 2] = ["rustc_lint", "LateContext"];
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pub const LIBC_STRLEN: [&str; 2] = ["libc", "strlen"];
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pub const LINKED_LIST: [&str; 4] = ["alloc", "collections", "linked_list", "LinkedList"];
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#[cfg(any(feature = "internal-lints", feature = "metadata-collector-lint"))]
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pub const LINT: [&str; 2] = ["rustc_lint_defs", "Lint"];
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@ -231,6 +231,17 @@ pub fn is_recursively_primitive_type(ty: Ty<'_>) -> bool {
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}
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}
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/// Checks if the type is a reference equals to a diagnostic item
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pub fn is_type_ref_to_diagnostic_item(cx: &LateContext<'_>, ty: Ty<'_>, diag_item: Symbol) -> bool {
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match ty.kind() {
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ty::Ref(_, ref_ty, _) => match ref_ty.kind() {
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ty::Adt(adt, _) => cx.tcx.is_diagnostic_item(diag_item, adt.did),
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_ => false,
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},
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_ => false,
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}
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}
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/// Checks if the type is equal to a diagnostic item
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///
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/// If you change the signature, remember to update the internal lint `MatchTypeOnDiagItem`
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16
tests/ui/strlen_on_c_strings.rs
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16
tests/ui/strlen_on_c_strings.rs
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@ -0,0 +1,16 @@
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#![warn(clippy::strlen_on_c_strings)]
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#![allow(dead_code)]
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#![feature(rustc_private)]
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extern crate libc;
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use std::ffi::{CStr, CString};
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fn main() {
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// 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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// CStr
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let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
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let len = unsafe { libc::strlen(cstr.as_ptr()) };
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}
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25
tests/ui/strlen_on_c_strings.stderr
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25
tests/ui/strlen_on_c_strings.stderr
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@ -0,0 +1,25 @@
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error: using `libc::strlen` on a `CString` or `CStr` value
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--> $DIR/strlen_on_c_strings.rs:11:24
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LL | let len = unsafe { libc::strlen(cstring.as_ptr()) };
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: `-D clippy::strlen-on-c-strings` implied by `-D warnings`
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help: try this (you might also need to get rid of `unsafe` block in some cases):
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LL | let len = unsafe { cstring.as_bytes().len() };
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| ^^^^^^^^^^^^^^^^^^^^^^^^
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error: using `libc::strlen` on a `CString` or `CStr` value
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--> $DIR/strlen_on_c_strings.rs:15:24
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LL | let len = unsafe { libc::strlen(cstr.as_ptr()) };
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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help: try this (you might also need to get rid of `unsafe` block in some cases):
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LL | let len = unsafe { cstr.to_bytes().len() };
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| ^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 2 previous errors
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