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Rollup merge of #130758 - compiler-errors:ctype-recursion-limit, r=jieyouxu

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Revert "Add recursion limit to FFI safety lint"

It's not necessarily clear if warning when we hit the recursion limit is the right thing to do, first of all.

**More importantly**, this PR was implemented incorrectly in the first place; it was not decrementing the recursion limit when stepping out of a type, so it would trigger when a ctype has more than RECURSION_LIMIT fields *anywhere* in the type's set of recursively reachable fields.

Reverts #130598
Reopens #130310
Fixes #130757
This commit is contained in:
Michael Goulet 2024-09-23 23:49:13 -04:00 • committed by GitHub
commit fa1bd9b06a
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6 changed files with 50 additions and 50 deletions
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20
compiler/rustc_lint/src/types.rs
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@ -592,8 +592,6 @@ struct CTypesVisitorState<'tcx> {
/// The original type being checked, before we recursed
/// to any other types it contains.
base_ty: Ty<'tcx>,
/// Number of times we recursed while checking the type
recursion_depth: usize,
}
enum FfiResult<'tcx> {
@ -899,23 +897,12 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
// Protect against infinite recursion, for example
// `struct S(*mut S);`.
// FIXME: A recursion limit is necessary as well, for irregular
// recursive types.
if !acc.cache.insert(ty) {
return FfiSafe;
}
// Additional recursion check for more complex types like
// `struct A<T> { v: *const A<A<T>>, ... }` for which the
// cache check above won't be enough (fixes #130310)
if !tcx.recursion_limit().value_within_limit(acc.recursion_depth) {
return FfiUnsafe {
ty: acc.base_ty,
reason: fluent::lint_improper_ctypes_recursion_limit_reached,
help: None,
};
}
acc.recursion_depth += 1;
match *ty.kind() {
ty::Adt(def, args) => {
if let Some(boxed) = ty.boxed_ty()
@ -1261,8 +1248,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
return;
}
let mut acc =
CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty, recursion_depth: 0 };
let mut acc = CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty };
match self.check_type_for_ffi(&mut acc, ty) {
FfiResult::FfiSafe => {}
FfiResult::FfiPhantom(ty) => {