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Remove surrounding unsafe block in strlen_on_c_strings when possible

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This commit is contained in:
Jason Newcomb 2021-11-19 20:51:20 -05:00
parent c443f8fb95
commit 0d1f1cec44
4 changed files with 131 additions and 34 deletions
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34
clippy_lints/src/strlen_on_c_strings.rs
View File

@ -1,10 +1,11 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::match_libc_symbol;
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;
@ -39,20 +40,31 @@
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<'_>) {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
if !expr.span.from_expansion();
if let hir::ExprKind::Call(func, [recv]) = expr.kind;
if let hir::ExprKind::Path(path) = &func.kind;
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 hir::ExprKind::MethodCall(path, _, [self_arg], _) = recv.kind;
if let ExprKind::MethodCall(path, _, [self_arg], _) = recv.kind;
if !recv.span.from_expansion();
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::Unspecified;
let val_name = snippet_with_context(cx, self_arg.span, expr.span.ctxt(), "..", &mut app).0;
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) {
@ -64,11 +76,11 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
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):",
"try this",
format!("{}.{}().len()", val_name, method_name),
Applicability::Unspecified // Sometimes unnecessary `unsafe` block
app,
);
}
}

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 @@ fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
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
}

12
tests/ui/strlen_on_c_strings.rs
View File

@ -16,4 +16,16 @@ fn main() {
let len = unsafe { libc::strlen(cstr.as_ptr()) };
let len = unsafe { strlen(cstr.as_ptr()) };
let pcstr: *const &CStr = &cstr;
let len = unsafe { strlen((*pcstr).as_ptr()) };
unsafe fn unsafe_identity<T>(x: T) -> T {
x
}
let len = unsafe { strlen(unsafe_identity(cstr).as_ptr()) };
let len = unsafe { strlen(unsafe { unsafe_identity(cstr) }.as_ptr()) };
let f: unsafe fn(_) -> _ = unsafe_identity;
let len = unsafe { strlen(f(cstr).as_ptr()) };
}

52
tests/ui/strlen_on_c_strings.stderr
View File

@ -1,36 +1,46 @@
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:12:24
--> $DIR/strlen_on_c_strings.rs:12:15
|
LL | let len = 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:16:24
--> $DIR/strlen_on_c_strings.rs:16:15
|
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() };
| ~~~~~~~~~~~~~~~~~~~~~
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:18:24
--> $DIR/strlen_on_c_strings.rs:18:15
|
LL | let len = unsafe { 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() };
| ~~~~~~~~~~~~~~~~~~~~~
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `cstr.to_bytes().len()`
error: aborting due to 3 previous errors
error: using `libc::strlen` on a `CString` or `CStr` value
--> $DIR/strlen_on_c_strings.rs:21:24
|
LL | let len = 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:26:24
|
LL | let len = 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:27:15
|
LL | let len = 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:30:24
|
LL | let len = unsafe { strlen(f(cstr).as_ptr()) };
| ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `f(cstr).to_bytes().len()`
error: aborting due to 7 previous errors