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use crate::LateContext;
use crate::LateLintPass;
use crate::LintContext;
use rustc_errors::fluent;
use rustc_hir::{Expr, ExprKind, PathSegment};
use rustc_middle::ty;
use rustc_span::{symbol::sym, ExpnKind, Span};
declare_lint! {
/// The `temporary_cstring_as_ptr` lint detects getting the inner pointer of
/// a temporary `CString`.
///
/// ### Example
///
/// ```rust
/// # #![allow(unused)]
/// # use std::ffi::CString;
/// let c_str = CString::new("foo").unwrap().as_ptr();
/// ```
///
/// {{produces}}
///
/// ### Explanation
///
/// The inner pointer of a `CString` lives only as long as the `CString` it
/// points to. Getting the inner pointer of a *temporary* `CString` allows the `CString`
/// to be dropped at the end of the statement, as it is not being referenced as far as the typesystem
/// is concerned. This means outside of the statement the pointer will point to freed memory, which
/// causes undefined behavior if the pointer is later dereferenced.
pub TEMPORARY_CSTRING_AS_PTR,
Warn,
"detects getting the inner pointer of a temporary `CString`"
}
declare_lint_pass!(TemporaryCStringAsPtr => [TEMPORARY_CSTRING_AS_PTR]);
fn in_macro(span: Span) -> bool {
if span.from_expansion() {
!matches!(span.ctxt().outer_expn_data().kind, ExpnKind::Desugaring(..))
} else {
false
}
}
fn first_method_call<'tcx>(
expr: &'tcx Expr<'tcx>,
) -> Option<(&'tcx PathSegment<'tcx>, &'tcx [Expr<'tcx>])> {
if let ExprKind::MethodCall(path, args, _) = &expr.kind {
if args.iter().any(|e| e.span.from_expansion()) { None } else { Some((path, *args)) }
} else {
None
}
}
impl<'tcx> LateLintPass<'tcx> for TemporaryCStringAsPtr {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if in_macro(expr.span) {
return;
}
match first_method_call(expr) {
Some((path, args)) if path.ident.name == sym::as_ptr => {
let unwrap_arg = &args[0];
let as_ptr_span = path.ident.span;
match first_method_call(unwrap_arg) {
Some((path, args))
if path.ident.name == sym::unwrap || path.ident.name == sym::expect =>
{
let source_arg = &args[0];
lint_cstring_as_ptr(cx, as_ptr_span, source_arg, unwrap_arg);
}
_ => return,
}
}
_ => return,
}
}
}
fn lint_cstring_as_ptr(
cx: &LateContext<'_>,
as_ptr_span: Span,
source: &rustc_hir::Expr<'_>,
unwrap: &rustc_hir::Expr<'_>,
) {
let source_type = cx.typeck_results().expr_ty(source);
if let ty::Adt(def, substs) = source_type.kind() {
if cx.tcx.is_diagnostic_item(sym::Result, def.did()) {
if let ty::Adt(adt, _) = substs.type_at(0).kind() {
if cx.tcx.is_diagnostic_item(sym::cstring_type, adt.did()) {
cx.struct_span_lint(TEMPORARY_CSTRING_AS_PTR, as_ptr_span, |diag| {
diag.build(fluent::lint::cstring_ptr)
.span_label(as_ptr_span, fluent::lint::as_ptr_label)
.span_label(unwrap.span, fluent::lint::unwrap_label)
.note(fluent::lint::note)
.help(fluent::lint::help)
.emit();
});
}
}
}
}
}
|
