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Add a special case for CStr/CString in the improper_ctypes lint

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Instead of saying to "consider adding a `#[repr(C)]` or
`#[repr(transparent)]` attribute to this struct", we now tell users to
"Use `*const ffi::c_char` instead, and pass the value from
`CStr::as_ptr()`" when the type involved is a `CStr` or a `CString`.

Co-authored-by: Jieyou Xu <jieyouxu@outlook.com>
This commit is contained in:
Flying-Toast 2024-03-23 10:49:05 -04:00 • committed by 许杰友 Jieyou Xu (Joe)
parent 93ea767e29
commit b335ec9ec8
7 changed files with 172 additions and 21 deletions
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54
compiler/rustc_lint/src/types.rs
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@ -984,6 +984,14 @@ struct ImproperCTypesVisitor<'a, 'tcx> {
mode: CItemKind,
}
/// Accumulator for recursive ffi type checking
struct CTypesVisitorState<'tcx> {
cache: FxHashSet<Ty<'tcx>>,
/// The original type being checked, before we recursed
/// to any other types it contains.
base_ty: Ty<'tcx>,
}
enum FfiResult<'tcx> {
FfiSafe,
FfiPhantom(Ty<'tcx>),
@ -1212,7 +1220,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
/// Checks if the given field's type is "ffi-safe".
fn check_field_type_for_ffi(
&self,
cache: &mut FxHashSet<Ty<'tcx>>,
acc: &mut CTypesVisitorState<'tcx>,
field: &ty::FieldDef,
args: GenericArgsRef<'tcx>,
) -> FfiResult<'tcx> {
@ -1222,13 +1230,13 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
.tcx
.try_normalize_erasing_regions(self.cx.param_env, field_ty)
.unwrap_or(field_ty);
self.check_type_for_ffi(cache, field_ty)
self.check_type_for_ffi(acc, field_ty)
}
/// Checks if the given `VariantDef`'s field types are "ffi-safe".
fn check_variant_for_ffi(
&self,
cache: &mut FxHashSet<Ty<'tcx>>,
acc: &mut CTypesVisitorState<'tcx>,
ty: Ty<'tcx>,
def: ty::AdtDef<'tcx>,
variant: &ty::VariantDef,
@ -1238,7 +1246,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
let transparent_with_all_zst_fields = if def.repr().transparent() {
if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
// Transparent newtypes have at most one non-ZST field which needs to be checked..
match self.check_field_type_for_ffi(cache, field, args) {
match self.check_field_type_for_ffi(acc, field, args) {
FfiUnsafe { ty, .. } if ty.is_unit() => (),
r => return r,
}
@ -1256,7 +1264,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
// We can't completely trust `repr(C)` markings, so make sure the fields are actually safe.
let mut all_phantom = !variant.fields.is_empty();
for field in &variant.fields {
all_phantom &= match self.check_field_type_for_ffi(cache, field, args) {
all_phantom &= match self.check_field_type_for_ffi(acc, field, args) {
FfiSafe => false,
// `()` fields are FFI-safe!
FfiUnsafe { ty, .. } if ty.is_unit() => false,
@ -1276,7 +1284,11 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
/// Checks if the given type is "ffi-safe" (has a stable, well-defined
/// representation which can be exported to C code).
fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
fn check_type_for_ffi(
&self,
acc: &mut CTypesVisitorState<'tcx>,
ty: Ty<'tcx>,
) -> FfiResult<'tcx> {
use FfiResult::*;
let tcx = self.cx.tcx;
@ -1285,7 +1297,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
// `struct S(*mut S);`.
// FIXME: A recursion limit is necessary as well, for irregular
// recursive types.
if !cache.insert(ty) {
if !acc.cache.insert(ty) {
return FfiSafe;
}
@ -1307,6 +1319,17 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
}
match def.adt_kind() {
AdtKind::Struct | AdtKind::Union => {
if let Some(sym::cstring_type | sym::cstr_type) =
tcx.get_diagnostic_name(def.did())
&& !acc.base_ty.is_mutable_ptr()
{
return FfiUnsafe {
ty,
reason: fluent::lint_improper_ctypes_cstr_reason,
help: Some(fluent::lint_improper_ctypes_cstr_help),
};
}
if !def.repr().c() && !def.repr().transparent() {
return FfiUnsafe {
ty,
@ -1353,7 +1376,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
};
}
self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), args)
self.check_variant_for_ffi(acc, ty, def, def.non_enum_variant(), args)
}
AdtKind::Enum => {
if def.variants().is_empty() {
@ -1377,7 +1400,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
if let Some(ty) =
repr_nullable_ptr(self.cx.tcx, self.cx.param_env, ty, self.mode)
{
return self.check_type_for_ffi(cache, ty);
return self.check_type_for_ffi(acc, ty);
}
return FfiUnsafe {
@ -1398,7 +1421,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
};
}
match self.check_variant_for_ffi(cache, ty, def, variant, args) {
match self.check_variant_for_ffi(acc, ty, def, variant, args) {
FfiSafe => (),
r => return r,
}
@ -1468,9 +1491,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
FfiSafe
}
ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(cache, ty),
ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(acc, ty),
ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
ty::Array(inner_ty, _) => self.check_type_for_ffi(acc, inner_ty),
ty::FnPtr(sig) => {
if self.is_internal_abi(sig.abi()) {
@ -1483,7 +1506,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
let sig = tcx.instantiate_bound_regions_with_erased(sig);
for arg in sig.inputs() {
match self.check_type_for_ffi(cache, *arg) {
match self.check_type_for_ffi(acc, *arg) {
FfiSafe => {}
r => return r,
}
@ -1494,7 +1517,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
return FfiSafe;
}
self.check_type_for_ffi(cache, ret_ty)
self.check_type_for_ffi(acc, ret_ty)
}
ty::Foreign(..) => FfiSafe,
@ -1617,7 +1640,8 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
return;
}
match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
let mut acc = CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty };
match self.check_type_for_ffi(&mut acc, ty) {
FfiResult::FfiSafe => {}
FfiResult::FfiPhantom(ty) => {
self.emit_ffi_unsafe_type_lint(