Commit 0bb532d2 authored by Xi Ruoyao's avatar Xi Ruoyao
Browse files

Bug 1841040 - Remove over-alignment from GCMarker and Nursery,... 

Bug 1841040 - Remove over-alignment from GCMarker and Nursery, r=spidermonkey-reviewers,jonco a=RyanVM

js_new<T> cannot guarantee the alignment if T is over-aligned, and this
issue is not trivial to fix (blocked by Bug 1842582).

Add a static assert to detect the attempt using js_new<T> for
over-aligned T, and remove the problematic alignas() attributes as a
short-term fix.

Differential Revision: https://phabricator.services.mozilla.com/D182546
parent 5805d10d

js/public/Utility.h

+6 −0
Original line number Diff line number Diff line
@@ -478,6 +478,9 @@ static inline void js_free(void* p) { 
#define JS_DECLARE_NEW_METHODS(NEWNAME, ALLOCATOR, QUALIFIERS)              \

  template <class T, typename... Args>                                      \

  QUALIFIERS T* MOZ_HEAP_ALLOCATOR NEWNAME(Args&&... args) {                \

    static_assert(                                                          \

        alignof(T) <= alignof(max_align_t),                                 \

        "over-aligned type is not supported by JS_DECLARE_NEW_METHODS");    \

    void* memory = ALLOCATOR(sizeof(T));                                    \

    return MOZ_LIKELY(memory) ? new (memory) T(std::forward<Args>(args)...) \

                              : nullptr;                                    \
@@ -494,6 +497,9 @@ static inline void js_free(void* p) { 
#define JS_DECLARE_NEW_ARENA_METHODS(NEWNAME, ALLOCATOR, QUALIFIERS)           \

  template <class T, typename... Args>                                         \

  QUALIFIERS T* MOZ_HEAP_ALLOCATOR NEWNAME(arena_id_t arena, Args&&... args) { \

    static_assert(                                                             \

        alignof(T) <= alignof(max_align_t),                                    \

        "over-aligned type is not supported by JS_DECLARE_NEW_ARENA_METHODS"); \

    void* memory = ALLOCATOR(arena, sizeof(T));                                \

    return MOZ_LIKELY(memory) ? new (memory) T(std::forward<Args>(args)...)    \

                              : nullptr;                                       \

js/src/gc/GCMarker.h

+1 −1
Original line number Diff line number Diff line
@@ -274,7 +274,7 @@ enum ShouldReportMarkTime : bool { 


} /* namespace gc */



class alignas(TypicalCacheLineSize) GCMarker {

class GCMarker {

  enum MarkingState : uint8_t {

    // Have not yet started marking.

    NotActive,

js/src/gc/Nursery.h

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ class GCSchedulingTunables; 
class TenuringTracer;

}  // namespace gc



class alignas(TypicalCacheLineSize) Nursery {

class Nursery {

 public:

  explicit Nursery(gc::GCRuntime* gc);

  ~Nursery();