//! Determining which types for which we cannot emit `#[derive(Trait)]`.
use std::fmt;
use super::{generate_dependencies, ConstrainResult, MonotoneFramework};
use crate::ir::analysis::has_vtable::HasVtable;
use crate::ir::comp::CompKind;
use crate::ir::context::{BindgenContext, ItemId};
use crate::ir::derive::CanDerive;
use crate::ir::function::FunctionSig;
use crate::ir::item::{IsOpaque, Item};
use crate::ir::layout::Layout;
use crate::ir::template::TemplateParameters;
use crate::ir::traversal::{EdgeKind, Trace};
use crate::ir::ty::RUST_DERIVE_IN_ARRAY_LIMIT;
use crate::ir::ty::{Type, TypeKind};
use crate::{Entry, HashMap, HashSet};
/// Which trait to consider when doing the `CannotDerive` analysis.
#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
pub enum DeriveTrait {
/// The `Copy` trait.
Copy,
/// The `Debug` trait.
Debug,
/// The `Default` trait.
Default,
/// The `Hash` trait.
Hash,
/// The `PartialEq` and `PartialOrd` traits.
PartialEqOrPartialOrd,
}
/// An analysis that finds for each IR item whether a trait cannot be derived.
///
/// We use the monotone constraint function `cannot_derive`, defined as follows
/// for type T:
///
/// * If T is Opaque and the layout of the type is known, get this layout as an
/// opaquetype and check whether it can derive using trivial checks.
///
/// * If T is Array, a trait cannot be derived if the array is incomplete,
/// if the length of the array is larger than the limit (unless the trait
/// allows it), or the trait cannot be derived for the type of data the array
/// contains.
///
/// * If T is Vector, a trait cannot be derived if the trait cannot be derived
/// for the type of data the vector contains.
///
/// * If T is a type alias, a templated alias or an indirection to another type,
/// the trait cannot be derived if the trait cannot be derived for type T
/// refers to.
///
/// * If T is a compound type, the trait cannot be derived if the trait cannot
/// be derived for any of its base members or fields.
///
/// * If T is an instantiation of an abstract template definition, the trait
/// cannot be derived if any of the template arguments or template definition
/// cannot derive the trait.
///
/// * For all other (simple) types, compiler and standard library limitations
/// dictate whether the trait is implemented.
#[derive(Debug, Clone)]
pub(crate) struct CannotDerive<'ctx> {
ctx: &'ctx BindgenContext,
derive_trait: DeriveTrait,
// The incremental result of this analysis's computation.
// Contains information whether particular item can derive `derive_trait`
can_derive: HashMap<ItemId, CanDerive>,
// Dependencies saying that if a key ItemId has been inserted into the
// `cannot_derive_partialeq_or_partialord` set, then each of the ids
// in Vec<ItemId> need to be considered again.
//
// This is a subset of the natural IR graph with reversed edges, where we
// only include the edges from the IR graph that can affect whether a type
// can derive `derive_trait`.
dependencies: HashMap<ItemId, Vec<ItemId>>,
}
type EdgePredicate = fn(EdgeKind) -> bool;
fn consider_edge_default(kind: EdgeKind) -> bool {
match kind {
// These are the only edges that can affect whether a type can derive
EdgeKind::BaseMember |
EdgeKind::Field |
EdgeKind::TypeReference |
EdgeKind::VarType |
EdgeKind::TemplateArgument |
EdgeKind::TemplateDeclaration |
EdgeKind::TemplateParameterDefinition => true,
EdgeKind::Constructor |
EdgeKind::Destructor |
EdgeKind::FunctionReturn |
EdgeKind::FunctionParameter |
EdgeKind::InnerType |
EdgeKind::InnerVar |
EdgeKind::Method |
EdgeKind::Generic => false,
}
}
impl<'ctx> CannotDerive<'ctx> {
fn insert<Id: Into<ItemId>>(
&mut self,
id: Id,
can_derive: CanDerive,
) -> ConstrainResult {
let id = id.into();
trace!(
"inserting {:?} can_derive<{}>={:?}",
id,
self.derive_trait,
can_derive
);
if let CanDerive::Yes = can_derive {
return ConstrainResult::Same;
}
match self.can_derive.entry(id) {
Entry::Occupied(mut entry) => {
if *entry.get() < can_derive {
entry.insert(can_derive);
ConstrainResult::Changed
} else {
ConstrainResult::Same
}
}
Entry::Vacant(entry) => {
entry.insert(can_derive);
ConstrainResult::Changed
}
}
}
fn constrain_type(&mut self, item: &Item, ty: &Type) -> CanDerive {
if !self.ctx.allowlisted_items().contains(&item.id()) {
let can_derive = self
.ctx
.blocklisted_type_implements_trait(item, self.derive_trait);
match can_derive {
CanDerive::Yes => trace!(
" blocklisted type explicitly implements {}",
self.derive_trait
),
CanDerive::Manually => trace!(
" blocklisted type requires manual implementation of {}",
self.derive_trait
),
CanDerive::No => trace!(
" cannot derive {} for blocklisted type",
self.derive_trait
),
}
return can_derive;
}
if self.derive_trait.not_by_name(self.ctx, item) {
trace!(
" cannot derive {} for explicitly excluded type",
self.derive_trait
);
return CanDerive::No;
}
trace!("ty: {:?}", ty);
if item.is_opaque(self.ctx, &()) {
if !self.derive_trait.can_derive_union() &&
ty.is_union() &&
self.ctx.options().untagged_union
{
trace!(
" cannot derive {} for Rust unions",
self.derive_trait
);
return CanDerive::No;
}
let layout_can_derive =
ty.layout(self.ctx).map_or(CanDerive::Yes, |l| {
l.opaque().array_size_within_derive_limit(self.ctx)
});
match layout_can_derive {
CanDerive::Yes => {
trace!(
" we can trivially derive {} for the layout",
self.derive_trait
);
}
_ => {
trace!(
" we cannot derive {} for the layout",
self.derive_trait
);
}
};
return layout_can_derive;
}
match *ty.kind() {
// Handle the simple cases. These can derive traits without further
// information.
TypeKind::Void |
TypeKind::NullPtr |
TypeKind::Int(..) |
TypeKind::Complex(..) |
TypeKind::Float(..) |
TypeKind::Enum(..) |
TypeKind::TypeParam |
TypeKind::UnresolvedTypeRef(..) |
TypeKind::Reference(..) |
TypeKind::ObjCInterface(..) |
TypeKind::ObjCId |
TypeKind::ObjCSel => {
return self.derive_trait.can_derive_simple(ty.kind());
}
TypeKind::Pointer(inner) => {
let inner_type =
self.ctx.resolve_type(inner).canonical_type(self.ctx);
if let TypeKind::Function(ref sig) = *inner_type.kind() {
self.derive_trait.can_derive_fnptr(sig)
} else {
self.derive_trait.can_derive_pointer()
}
}
TypeKind::Function(ref sig) => {
self.derive_trait.can_derive_fnptr(sig)
}
// Complex cases need more information
TypeKind::Array(t, len) => {
let inner_type =
self.can_derive.get(&t.into()).cloned().unwrap_or_default();
if inner_type != CanDerive::Yes {
trace!(
" arrays of T for which we cannot derive {} \
also cannot derive {}",
self.derive_trait,
self.derive_trait
);
return CanDerive::No;
}
if len == 0 && !self.derive_trait.can_derive_incomplete_array()
{
trace!(
" cannot derive {} for incomplete arrays",
self.derive_trait
);
return CanDerive::No;
}
if self.derive_trait.can_derive_large_array(self.ctx) {
trace!(" array can derive {}", self.derive_trait);
return CanDerive::Yes;
}
if len > RUST_DERIVE_IN_ARRAY_LIMIT {
trace!(
" array is too large to derive {}, but it may be implemented", self.derive_trait
);
return CanDerive::Manually;
}
trace!(
" array is small enough to derive {}",
self.derive_trait
);
CanDerive::Yes
}
TypeKind::Vector(t, len) => {
let inner_type =
self.can_derive.get(&t.into()).cloned().unwrap_or_default();
if inner_type != CanDerive::Yes {
trace!(
" vectors of T for which we cannot derive {} \
also cannot derive {}",
self.derive_trait,
self.derive_trait
);
return CanDerive::No;
}
assert_ne!(len, 0, "vectors cannot have zero length");
self.derive_trait.can_derive_vector()
}
TypeKind::Comp(ref info) => {
assert!(
!info.has_non_type_template_params(),
"The early ty.is_opaque check should have handled this case"
);
if !self.derive_trait.can_derive_compound_forward_decl() &&
info.is_forward_declaration()
{
trace!(
" cannot derive {} for forward decls",
self.derive_trait
);
return CanDerive::No;
}
// NOTE: Take into account that while unions in C and C++ are copied by
// default, the may have an explicit destructor in C++, so we can't
// defer this check just for the union case.
if !self.derive_trait.can_derive_compound_with_destructor() &&
self.ctx.lookup_has_destructor(
item.id().expect_type_id(self.ctx),
)
{
trace!(
" comp has destructor which cannot derive {}",
self.derive_trait
);
return CanDerive::No;
}
if info.kind() == CompKind::Union {
if self.derive_trait.can_derive_union() {
if self.ctx.options().untagged_union &&
//
https://github.com/rust-lang/rust/issues/36640
(!info.self_template_params(self.ctx).is_empty() ||
!item.all_template_params(self.ctx).is_empty())
{
trace!(
" cannot derive {} for Rust union because issue 36640", self.derive_trait
);
return CanDerive::No;
}
// fall through to be same as non-union handling
} else {
if self.ctx.options().untagged_union {
trace!(
" cannot derive {} for Rust unions",
self.derive_trait
);
return CanDerive::No;
}
let layout_can_derive =
ty.layout(self.ctx).map_or(CanDerive::Yes, |l| {
l.opaque()
.array_size_within_derive_limit(self.ctx)
});
match layout_can_derive {
CanDerive::Yes => {
trace!(
" union layout can trivially derive {}",
self.derive_trait
);
}
_ => {
trace!(
" union layout cannot derive {}",
self.derive_trait
);
}
};
return layout_can_derive;
}
}
if !self.derive_trait.can_derive_compound_with_vtable() &&
item.has_vtable(self.ctx)
{
trace!(
" cannot derive {} for comp with vtable",
self.derive_trait
);
return CanDerive::No;
}
// Bitfield units are always represented as arrays of u8, but
// they're not traced as arrays, so we need to check here
// instead.
if !self.derive_trait.can_derive_large_array(self.ctx) &&
info.has_too_large_bitfield_unit() &&
!item.is_opaque(self.ctx, &())
{
trace!(
" cannot derive {} for comp with too large bitfield unit",
self.derive_trait
);
return CanDerive::No;
}
let pred = self.derive_trait.consider_edge_comp();
self.constrain_join(item, pred)
}
TypeKind::ResolvedTypeRef(..) |
TypeKind::TemplateAlias(..) |
TypeKind::Alias(..) |
TypeKind::BlockPointer(..) => {
let pred = self.derive_trait.consider_edge_typeref();
self.constrain_join(item, pred)
}
TypeKind::TemplateInstantiation(..) => {
let pred = self.derive_trait.consider_edge_tmpl_inst();
self.constrain_join(item, pred)
}
TypeKind::Opaque => unreachable!(
"The early ty.is_opaque check should have handled this case"
),
}
}
fn constrain_join(
&mut self,
item: &Item,
consider_edge: EdgePredicate,
) -> CanDerive {
let mut candidate = None;
item.trace(
self.ctx,
&mut |sub_id, edge_kind| {
// Ignore ourselves, since union with ourself is a
// no-op. Ignore edges that aren't relevant to the
// analysis.
if sub_id == item.id() || !consider_edge(edge_kind) {
return;
}
let can_derive = self.can_derive
.get(&sub_id)
.cloned()
.unwrap_or_default();
match can_derive {
CanDerive::Yes => trace!(" member {:?} can derive {}", sub_id, self.derive_trait),
CanDerive::Manually => trace!(" member {:?} cannot derive {}, but it may be implemented", sub_
id, self.derive_trait),
CanDerive::No => trace!(" member {:?} cannot derive {}", sub_id, self.derive_trait),
}
*candidate.get_or_insert(CanDerive::Yes) |= can_derive;
},
&(),
);
if candidate.is_none() {
trace!(
" can derive {} because there are no members",
self.derive_trait
);
}
candidate.unwrap_or_default()
}
}
impl DeriveTrait {
fn not_by_name(&self, ctx: &BindgenContext, item: &Item) -> bool {
match self {
DeriveTrait::Copy => ctx.no_copy_by_name(item),
DeriveTrait::Debug => ctx.no_debug_by_name(item),
DeriveTrait::Default => ctx.no_default_by_name(item),
DeriveTrait::Hash => ctx.no_hash_by_name(item),
DeriveTrait::PartialEqOrPartialOrd => {
ctx.no_partialeq_by_name(item)
}
}
}
fn consider_edge_comp(&self) -> EdgePredicate {
match self {
DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
_ => |kind| matches!(kind, EdgeKind::BaseMember | EdgeKind::Field),
}
}
fn consider_edge_typeref(&self) -> EdgePredicate {
match self {
DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
_ => |kind| kind == EdgeKind::TypeReference,
}
}
fn consider_edge_tmpl_inst(&self) -> EdgePredicate {
match self {
DeriveTrait::PartialEqOrPartialOrd => consider_edge_default,
_ => |kind| {
matches!(
kind,
EdgeKind::TemplateArgument | EdgeKind::TemplateDeclaration
)
},
}
}
fn can_derive_large_array(&self, ctx: &BindgenContext) -> bool {
if ctx.options().rust_features().larger_arrays {
!matches!(self, DeriveTrait::Default)
} else {
matches!(self, DeriveTrait::Copy)
}
}
fn can_derive_union(&self) -> bool {
matches!(self, DeriveTrait::Copy)
}
fn can_derive_compound_with_destructor(&self) -> bool {
!matches!(self, DeriveTrait::Copy)
}
fn can_derive_compound_with_vtable(&self) -> bool {
!matches!(self, DeriveTrait::Default)
}
fn can_derive_compound_forward_decl(&self) -> bool {
matches!(self, DeriveTrait::Copy | DeriveTrait::Debug)
}
fn can_derive_incomplete_array(&self) -> bool {
!matches!(
self,
DeriveTrait::Copy |
DeriveTrait::Hash |
DeriveTrait::PartialEqOrPartialOrd
)
}
fn can_derive_fnptr(&self, f: &FunctionSig) -> CanDerive {
match (self, f.function_pointers_can_derive()) {
(DeriveTrait::Copy, _) | (DeriveTrait::Default, _) | (_, true) => {
trace!(" function pointer can derive {}", self);
CanDerive::Yes
}
(DeriveTrait::Debug, false) => {
trace!(" function pointer cannot derive {}, but it may be implemented", self);
CanDerive::Manually
}
(_, false) => {
trace!(" function pointer cannot derive {}", self);
CanDerive::No
}
}
}
fn can_derive_vector(&self) -> CanDerive {
match self {
DeriveTrait::PartialEqOrPartialOrd => {
// FIXME: vectors always can derive PartialEq, but they should
// not derive PartialOrd:
// https://github.com/rust-lang-nursery/packed_simd/issues/48
trace!(" vectors cannot derive PartialOrd");
CanDerive::No
}
_ => {
trace!(" vector can derive {}", self);
CanDerive::Yes
}
}
}
fn can_derive_pointer(&self) -> CanDerive {
match self {
DeriveTrait::Default => {
trace!(" pointer cannot derive Default");
CanDerive::No
}
_ => {
trace!(" pointer can derive {}", self);
CanDerive::Yes
}
}
}
fn can_derive_simple(&self, kind: &TypeKind) -> CanDerive {
match (self, kind) {
// === Default ===
(DeriveTrait::Default, TypeKind::Void) |
(DeriveTrait::Default, TypeKind::NullPtr) |
(DeriveTrait::Default, TypeKind::Enum(..)) |
(DeriveTrait::Default, TypeKind::Reference(..)) |
(DeriveTrait::Default, TypeKind::TypeParam) |
(DeriveTrait::Default, TypeKind::ObjCInterface(..)) |
(DeriveTrait::Default, TypeKind::ObjCId) |
(DeriveTrait::Default, TypeKind::ObjCSel) => {
trace!(" types that always cannot derive Default");
CanDerive::No
}
(DeriveTrait::Default, TypeKind::UnresolvedTypeRef(..)) => {
unreachable!(
"Type with unresolved type ref can't reach derive default"
)
}
// === Hash ===
(DeriveTrait::Hash, TypeKind::Float(..)) |
(DeriveTrait::Hash, TypeKind::Complex(..)) => {
trace!(" float cannot derive Hash");
CanDerive::No
}
// === others ===
_ => {
trace!(" simple type that can always derive {}", self);
CanDerive::Yes
}
}
}
}
impl fmt::Display for DeriveTrait {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let s = match self {
DeriveTrait::Copy => "Copy",
DeriveTrait::Debug => "Debug",
DeriveTrait::Default => "Default",
DeriveTrait::Hash => "Hash",
DeriveTrait::PartialEqOrPartialOrd => "PartialEq/PartialOrd",
};
s.fmt(f)
}
}
impl<'ctx> MonotoneFramework for CannotDerive<'ctx> {
type Node = ItemId;
type Extra = (&'ctx BindgenContext, DeriveTrait);
type Output = HashMap<ItemId, CanDerive>;
fn new(
(ctx, derive_trait): (&'ctx BindgenContext, DeriveTrait),
) -> CannotDerive<'ctx> {
let can_derive = HashMap::default();
let dependencies = generate_dependencies(ctx, consider_edge_default);
CannotDerive {
ctx,
derive_trait,
can_derive,
dependencies,
}
}
fn initial_worklist(&self) -> Vec<ItemId> {
// The transitive closure of all allowlisted items, including explicitly
// blocklisted items.
self.ctx
.allowlisted_items()
.iter()
.cloned()
.flat_map(|i| {
let mut reachable = vec![i];
i.trace(
self.ctx,
&mut |s, _| {
reachable.push(s);
},
&(),
);
reachable
})
.collect()
}
fn constrain(&mut self, id: ItemId) -> ConstrainResult {
trace!("constrain: {:?}", id);
if let Some(CanDerive::No) = self.can_derive.get(&id).cloned() {
trace!(" already know it cannot derive {}", self.derive_trait);
return ConstrainResult::Same;
}
let item = self.ctx.resolve_item(id);
let can_derive = match item.as_type() {
Some(ty) => {
let mut can_derive = self.constrain_type(item, ty);
if let CanDerive::Yes = can_derive {
let is_reached_limit =
|l: Layout| l.align > RUST_DERIVE_IN_ARRAY_LIMIT;
if !self.derive_trait.can_derive_large_array(self.ctx) &&
ty.layout(self.ctx).map_or(false, is_reached_limit)
{
// We have to be conservative: the struct *could* have enough
// padding that we emit an array that is longer than
// `RUST_DERIVE_IN_ARRAY_LIMIT`. If we moved padding calculations
// into the IR and computed them before this analysis, then we could
// be precise rather than conservative here.
can_derive = CanDerive::Manually;
}
}
can_derive
}
None => self.constrain_join(item, consider_edge_default),
};
self.insert(id, can_derive)
}
fn each_depending_on<F>(&self, id: ItemId, mut f: F)
where
F: FnMut(ItemId),
{
if let Some(edges) = self.dependencies.get(&id) {
for item in edges {
trace!("enqueue {:?} into worklist", item);
f(*item);
}
}
}
}
impl<'ctx> From<CannotDerive<'ctx>> for HashMap<ItemId, CanDerive> {
fn from(analysis: CannotDerive<'ctx>) -> Self {
extra_assert!(analysis
.can_derive
.values()
.all(|v| *v != CanDerive::Yes));
analysis.can_derive
}
}
/// Convert a `HashMap<ItemId, CanDerive>` into a `HashSet<ItemId>`.
///
/// Elements that are not `CanDerive::Yes` are kept in the set, so that it
/// represents all items that cannot derive.
pub(crate) fn as_cannot_derive_set(
can_derive: HashMap<ItemId, CanDerive>,
) -> HashSet<ItemId> {
can_derive
.into_iter()
.filter_map(|(k, v)| if v != CanDerive::Yes { Some(k) } else { None })
.collect()
}
