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Bug 1716247 - Add js::RootedUntypedBase type. r=sfink

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Add a common base type with the template parameter erased. This lets us remove
the RootListEntry type and the undefined reinterpret_casts it is using.

Depends on D117604

Differential Revision: https://phabricator.services.mozilla.com/D117605
This commit is contained in:
Ted Campbell 2021-06-15 17:34:33 +00:00
parent 7140f4571a
commit c987af278f
2 changed files with 15 additions and 31 deletions
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38
js/public/RootingAPI.h
View File

@ -124,8 +124,11 @@ template <typename Element, typename Wrapper>
class MutableWrappedPtrOperations
: public WrappedPtrOperations<Element, Wrapper> {};
class RootedUntypedBase {};
template <typename T, typename Wrapper>
class RootedBase : public MutableWrappedPtrOperations<T, Wrapper> {};
class RootedBase : public RootedUntypedBase,
public MutableWrappedPtrOperations<T, Wrapper> {};
template <typename T, typename Wrapper>
class HandleBase : public WrappedPtrOperations<T, Wrapper> {};
@ -926,22 +929,8 @@ enum class AutoGCRooterKind : uint8_t {
Limit
};
namespace detail {
// Dummy type to store root list entry pointers as. This code does not just use
// the actual type, because then eg JSObject* and JSFunction* would be assumed
// to never alias but they do (they are stored in the same list). Also, do not
// use `void*` so that `Rooted<void*>` is a compile error.
struct RootListEntry;
} // namespace detail
template <>
struct MapTypeToRootKind<detail::RootListEntry*> {
static const RootKind kind = RootKind::Traceable;
};
using RootedListHeads =
mozilla::EnumeratedArray<RootKind, RootKind::Limit,
Rooted<detail::RootListEntry*>*>;
mozilla::EnumeratedArray<RootKind, RootKind::Limit, js::RootedUntypedBase*>;
using AutoRooterListHeads =
mozilla::EnumeratedArray<AutoGCRooterKind, AutoGCRooterKind::Limit,
@ -1109,7 +1098,7 @@ class MOZ_RAII Rooted : public js::RootedBase<T, Rooted<T>> {
inline void registerWithRootLists(RootedListHeads& roots) {
this->stack = &roots[JS::MapTypeToRootKind<T>::kind];
this->prev = *stack;
*stack = reinterpret_cast<Rooted<detail::RootListEntry*>*>(this);
*stack = this;
}
inline RootedListHeads& rootLists(RootingContext* cx) {
@ -1159,8 +1148,7 @@ class MOZ_RAII Rooted : public js::RootedBase<T, Rooted<T>> {
}
~Rooted() {
MOZ_ASSERT(*stack ==
reinterpret_cast<Rooted<detail::RootListEntry*>*>(this));
MOZ_ASSERT(*stack == this);
*stack = prev;
}
@ -1191,13 +1179,8 @@ class MOZ_RAII Rooted : public js::RootedBase<T, Rooted<T>> {
void trace(JSTracer* trc, const char* name);
private:
/*
* These need to be templated on RootListEntry* to avoid aliasing issues
* between, for example, Rooted<JSObject*> and Rooted<JSFunction*>, which use
* the same stack head pointer for different classes.
*/
Rooted<detail::RootListEntry*>** stack;
Rooted<detail::RootListEntry*>* prev;
js::RootedUntypedBase** stack;
js::RootedUntypedBase* prev;
Ptr ptr;
@ -1260,7 +1243,8 @@ inline ProfilingStack* GetContextProfilingStackIfEnabled(JSContext* cx) {
*/
template <typename Container>
class RootedBase<JSObject*, Container>
: public MutableWrappedPtrOperations<JSObject*, Container> {
: public RootedUntypedBase,
public MutableWrappedPtrOperations<JSObject*, Container> {
public:
template <class U>
JS::Handle<U*> as() const;

8
js/src/gc/RootMarking.cpp
View File

@ -75,10 +75,10 @@ inline void JS::PersistentRooted<T>::trace(JSTracer* trc, const char* name) {
}
template <typename T>
static inline void TraceExactStackRootList(
JSTracer* trc, JS::Rooted<JS::detail::RootListEntry*>* listHead,
const char* name) {
auto* typedList = reinterpret_cast<JS::Rooted<T>*>(listHead);
static inline void TraceExactStackRootList(JSTracer* trc,
RootedUntypedBase* listHead,
const char* name) {
auto* typedList = static_cast<JS::Rooted<T>*>(listHead);
for (JS::Rooted<T>* root = typedList; root; root = root->previous()) {
root->trace(trc, name);
}