rust-clippy/clippy_lints/src/strlen_on_c_strings.rs

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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::visitors::is_expr_unsafe;
use clippy_utils::{get_parent_node, match_libc_symbol};
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use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Block, BlockCheckMode, Expr, ExprKind, Node, UnsafeSource};
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use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::sym;
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declare_clippy_lint! {
/// ### 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.
///
/// ### Why is this bad?
/// This avoids calling an unsafe `libc` function.
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/// Currently, it also avoids calculating the length.
///
/// ### Example
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/// ```rust, ignore
/// use std::ffi::CString;
/// let cstring = CString::new("foo").expect("CString::new failed");
/// let len = unsafe { libc::strlen(cstring.as_ptr()) };
/// ```
/// Use instead:
/// ```rust, no_run
/// use std::ffi::CString;
/// let cstring = CString::new("foo").expect("CString::new failed");
/// let len = cstring.as_bytes().len();
/// ```
Added `clippy::version` attribute to all normal lints So, some context for this, well, more a story. I'm not used to scripting, I've never really scripted anything, even if it's a valuable skill. I just never really needed it. Now, `@flip1995` correctly suggested using a script for this in `rust-clippy#7813`... And I decided to write a script using nushell because why not? This was a mistake... I spend way more time on this than I would like to admit. It has definitely been more than 4 hours. It shouldn't take that long, but me being new to scripting and nushell just wasn't a good mixture... Anyway, here is the script that creates another script which adds the versions. Fun... Just execute this on the `gh-pages` branch and the resulting `replacer.sh` in `clippy_lints` and it should all work. ```nu mv v0.0.212 rust-1.00.0; mv beta rust-1.57.0; mv master rust-1.58.0; let paths = (open ./rust-1.58.0/lints.json | select id id_span | flatten | select id path); let versions = ( ls | where name =~ "rust-" | select name | format {name}/lints.json | each { open $it | select id | insert version $it | str substring "5,11" version} | group-by id | rotate counter-clockwise id version | update version {get version | first 1} | flatten | select id version); $paths | each { |row| let version = ($versions | where id == ($row.id) | format {version}) let idu = ($row.id | str upcase) $"sed -i '0,/($idu),/{s/pub ($idu),/#[clippy::version = "($version)"]\n pub ($idu),/}' ($row.path)" } | str collect ";" | str find-replace --all '1.00.0' 'pre 1.29.0' | save "replacer.sh"; ``` And this still has some problems, but at this point I just want to be done -.-
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#[clippy::version = "1.55.0"]
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pub STRLEN_ON_C_STRINGS,
complexity,
"using `libc::strlen` on a `CString` or `CStr` value, while `as_bytes().len()` or `to_bytes().len()` respectively can be used instead"
}
declare_lint_pass!(StrlenOnCStrings => [STRLEN_ON_C_STRINGS]);
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impl<'tcx> LateLintPass<'tcx> for StrlenOnCStrings {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
if !expr.span.from_expansion();
if let ExprKind::Call(func, [recv]) = expr.kind;
if let ExprKind::Path(path) = &func.kind;
if let Some(did) = cx.qpath_res(path, func.hir_id).opt_def_id();
if match_libc_symbol(cx, did, "strlen");
if let ExprKind::MethodCall(path, _, [self_arg], _) = recv.kind;
if !recv.span.from_expansion();
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if path.ident.name == sym::as_ptr;
then {
let ctxt = expr.span.ctxt();
let span = match get_parent_node(cx.tcx, expr.hir_id) {
Some(Node::Block(&Block {
rules: BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided), span, ..
}))
if span.ctxt() == ctxt && !is_expr_unsafe(cx, self_arg) => {
span
}
_ => expr.span,
};
let ty = cx.typeck_results().expr_ty(self_arg).peel_refs();
let mut app = Applicability::MachineApplicable;
let val_name = snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0;
let method_name = if is_type_diagnostic_item(cx, ty, sym::cstring_type) {
"as_bytes"
} else if is_type_diagnostic_item(cx, ty, sym::CStr) {
"to_bytes"
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} else {
return;
};
span_lint_and_sugg(
cx,
STRLEN_ON_C_STRINGS,
span,
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"using `libc::strlen` on a `CString` or `CStr` value",
"try this",
format!("{}.{}().len()", val_name, method_name),
app,
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);
}
}
}
}