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Auto merge of #8001 - Jarcho:unprefixed_strlen, r=giraffate

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Improve `strlen_on_c_string`

fixes: #7436

changelog: lint `strlen_on_c_string` when used without a fully-qualified path
changelog: suggest removing the surrounding unsafe block for `strlen_on_c_string` when possible
This commit is contained in:
bors 2021-11-29 01:03:48 +00:00
commit 908815ce98
7 changed files with 200 additions and 50 deletions
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65
clippy_lints/src/strlen_on_c_strings.rs
View file

@ -1,13 +1,14 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::paths;
use clippy_utils::source::snippet_with_macro_callsite;
use clippy_utils::ty::{is_type_diagnostic_item, is_type_ref_to_diagnostic_item};
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};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::{Block, BlockCheckMode, Expr, ExprKind, Node, UnsafeSource};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::{sym, Symbol};
use rustc_span::symbol::sym;
declare_clippy_lint! {
/// ### What it does
@ -39,29 +40,35 @@ declare_clippy_lint! {
declare_lint_pass!(StrlenOnCStrings => [STRLEN_ON_C_STRINGS]);
impl LateLintPass<'tcx> for StrlenOnCStrings {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
if expr.span.from_expansion() {
return;
}
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
if let hir::ExprKind::Call(func, [recv]) = expr.kind;
if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = func.kind;
if (&paths::LIBC_STRLEN).iter().map(|x| Symbol::intern(x)).eq(
path.segments.iter().map(|seg| seg.ident.name));
if let hir::ExprKind::MethodCall(path, _, args, _) = recv.kind;
if args.len() == 1;
if !args.iter().any(|e| e.span.from_expansion());
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();
if path.ident.name == sym::as_ptr;
then {
let cstring = &args[0];
let ty = cx.typeck_results().expr_ty(cstring);
let val_name = snippet_with_macro_callsite(cx, cstring.span, "..");
let sugg = if is_type_diagnostic_item(cx, ty, sym::cstring_type){
format!("{}.as_bytes().len()", val_name)
} else if is_type_ref_to_diagnostic_item(cx, ty, sym::CStr){
format!("{}.to_bytes().len()", val_name)
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"
} else {
return;
};
@ -69,11 +76,11 @@ impl LateLintPass<'tcx> for StrlenOnCStrings {
span_lint_and_sugg(
cx,
STRLEN_ON_C_STRINGS,
expr.span,
span,
"using `libc::strlen` on a `CString` or `CStr` value",
"try this (you might also need to get rid of `unsafe` block in some cases):",
sugg,
Applicability::Unspecified // Sometimes unnecessary `unsafe` block
"try this",
format!("{}.{}().len()", val_name, method_name),
app,
);
}
}

8
clippy_utils/src/lib.rs
View file

@ -1597,6 +1597,14 @@ pub fn match_def_path<'tcx>(cx: &LateContext<'tcx>, did: DefId, syms: &[&str]) -
syms.iter().map(|x| Symbol::intern(x)).eq(path.iter().copied())
}
/// Checks if the given `DefId` matches the `libc` item.
pub fn match_libc_symbol(cx: &LateContext<'_>, did: DefId, name: &str) -> bool {
let path = cx.get_def_path(did);
// libc is meant to be used as a flat list of names, but they're all actually defined in different
// modules based on the target platform. Ignore everything but crate name and the item name.
path.first().map_or(false, |s| s.as_str() == "libc") && path.last().map_or(false, |s| s.as_str() == name)
}
pub fn match_panic_call(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
if let ExprKind::Call(func, [arg]) = expr.kind {
expr_path_res(cx, func)

1
clippy_utils/src/paths.rs
View file

@ -86,7 +86,6 @@ pub const ITERTOOLS_NEXT_TUPLE: [&str; 3] = ["itertools", "Itertools", "next_tup
pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
#[cfg(feature = "internal-lints")]
pub const LATE_CONTEXT: [&str; 2] = ["rustc_lint", "LateContext"];
pub const LIBC_STRLEN: [&str; 2] = ["libc", "strlen"];
#[cfg(any(feature = "internal-lints", feature = "metadata-collector-lint"))]
pub const LINT: [&str; 2] = ["rustc_lint_defs", "Lint"];
pub const MEM_DISCRIMINANT: [&str; 3] = ["core", "mem", "discriminant"];

67
clippy_utils/src/visitors.rs
View file

@ -1,8 +1,10 @@
use crate::path_to_local_id;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::intravisit::{self, walk_expr, NestedVisitorMap, Visitor};
use rustc_hir::{Arm, Block, Body, BodyId, Expr, ExprKind, HirId, Stmt, UnOp};
use rustc_hir::intravisit::{self, walk_block, walk_expr, NestedVisitorMap, Visitor};
use rustc_hir::{
Arm, Block, BlockCheckMode, Body, BodyId, Expr, ExprKind, HirId, ItemId, ItemKind, Stmt, UnOp, Unsafety,
};
use rustc_lint::LateContext;
use rustc_middle::hir::map::Map;
use rustc_middle::ty;
@ -317,3 +319,64 @@ pub fn is_const_evaluatable(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
v.visit_expr(e);
v.is_const
}
/// Checks if the given expression performs an unsafe operation outside of an unsafe block.
pub fn is_expr_unsafe(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
struct V<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
is_unsafe: bool,
}
impl<'tcx> Visitor<'tcx> for V<'_, 'tcx> {
type Map = Map<'tcx>;
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
}
fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
if self.is_unsafe {
return;
}
match e.kind {
ExprKind::Unary(UnOp::Deref, e) if self.cx.typeck_results().expr_ty(e).is_unsafe_ptr() => {
self.is_unsafe = true;
},
ExprKind::MethodCall(..)
if self
.cx
.typeck_results()
.type_dependent_def_id(e.hir_id)
.map_or(false, |id| self.cx.tcx.fn_sig(id).unsafety() == Unsafety::Unsafe) =>
{
self.is_unsafe = true;
},
ExprKind::Call(func, _) => match *self.cx.typeck_results().expr_ty(func).peel_refs().kind() {
ty::FnDef(id, _) if self.cx.tcx.fn_sig(id).unsafety() == Unsafety::Unsafe => self.is_unsafe = true,
ty::FnPtr(sig) if sig.unsafety() == Unsafety::Unsafe => self.is_unsafe = true,
_ => walk_expr(self, e),
},
ExprKind::Path(ref p)
if self
.cx
.qpath_res(p, e.hir_id)
.opt_def_id()
.map_or(false, |id| self.cx.tcx.is_mutable_static(id)) =>
{
self.is_unsafe = true;
},
_ => walk_expr(self, e),
}
}
fn visit_block(&mut self, b: &'tcx Block<'_>) {
if !matches!(b.rules, BlockCheckMode::UnsafeBlock(_)) {
walk_block(self, b);
}
}
fn visit_nested_item(&mut self, id: ItemId) {
if let ItemKind::Impl(i) = &self.cx.tcx.hir().item(id).kind {
self.is_unsafe = i.unsafety == Unsafety::Unsafe;
}
}
}
let mut v = V { cx, is_unsafe: false };
v.visit_expr(e);
v.is_unsafe
}

34
tests/ui/strlen_on_c_strings.fixed Normal file
View file

@ -0,0 +1,34 @@
// run-rustfix
#![warn(clippy::strlen_on_c_strings)]
#![allow(dead_code)]
#![feature(rustc_private)]
extern crate libc;
#[allow(unused)]
use libc::strlen;
use std::ffi::{CStr, CString};
fn main() {
// CString
let cstring = CString::new("foo").expect("CString::new failed");
let _ = cstring.as_bytes().len();
// CStr
let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
let _ = cstr.to_bytes().len();
let _ = cstr.to_bytes().len();
let pcstr: *const &CStr = &cstr;
let _ = unsafe { (*pcstr).to_bytes().len() };
unsafe fn unsafe_identity<T>(x: T) -> T {
x
}
let _ = unsafe { unsafe_identity(cstr).to_bytes().len() };
let _ = unsafe { unsafe_identity(cstr) }.to_bytes().len();
let f: unsafe fn(_) -> _ = unsafe_identity;
let _ = unsafe { f(cstr).to_bytes().len() };
}

22
tests/ui/strlen_on_c_strings.rs
View file

@ -1,16 +1,34 @@
// run-rustfix
#![warn(clippy::strlen_on_c_strings)]
#![allow(dead_code)]
#![feature(rustc_private)]
extern crate libc;
#[allow(unused)]
use libc::strlen;
use std::ffi::{CStr, CString};
fn main() {
// CString
let cstring = CString::new("foo").expect("CString::new failed");
let len = unsafe { libc::strlen(cstring.as_ptr()) };
let _ = unsafe { libc::strlen(cstring.as_ptr()) };
// CStr
let cstr = CStr::from_bytes_with_nul(b"foo\0").expect("CStr::from_bytes_with_nul failed");
let len = unsafe { libc::strlen(cstr.as_ptr()) };
let _ = unsafe { libc::strlen(cstr.as_ptr()) };
let _ = unsafe { strlen(cstr.as_ptr()) };
let pcstr: *const &CStr = &cstr;
let _ = unsafe { strlen((*pcstr).as_ptr()) };
unsafe fn unsafe_identity<T>(x: T) -> T {
x
}
let _ = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
let _ = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
let f: unsafe fn(_) -> _ = unsafe_identity;
let _ = unsafe { strlen(f(cstr).as_ptr()) };
}

53
tests/ui/strlen_on_c_strings.stderr
View file

@ -1,25 +1,46 @@
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:11:24
--> $DIR/strlen_on_c_strings.rs:15:13
|
LL | let len = unsafe { libc::strlen(cstring.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
LL | let _ = unsafe { libc::strlen(cstring.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstring.as_bytes().len()`
|
= note: `-D clippy::strlen-on-c-strings` implied by `-D warnings`
help: try this (you might also need to get rid of `unsafe` block in some cases):
|
LL | let len = unsafe { cstring.as_bytes().len() };
| ~~~~~~~~~~~~~~~~~~~~~~~~
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:15:24
--> $DIR/strlen_on_c_strings.rs:19:13
|
LL | let len = unsafe { libc::strlen(cstr.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: try this (you might also need to get rid of `unsafe` block in some cases):
|
LL | let len = unsafe { cstr.to_bytes().len() };
| ~~~~~~~~~~~~~~~~~~~~~
LL | let _ = unsafe { libc::strlen(cstr.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
error: aborting due to 2 previous errors
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:21:13
|
LL | let _ = unsafe { strlen(cstr.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:24:22
|
LL | let _ = unsafe { strlen((*pcstr).as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `(*pcstr).to_bytes().len()`
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:29:22
|
LL | let _ = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe_identity(cstr).to_bytes().len()`
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:30:13
|
LL | let _ = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unsafe { unsafe_identity(cstr) }.to_bytes().len()`
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:33:22
|
LL | let _ = unsafe { strlen(f(cstr).as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `f(cstr).to_bytes().len()`
error: aborting due to 7 previous errors