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Commit c0df68bb authored by Hans Boehm's avatar Hans Boehm
Browse files

Work around C11 const atomic restrictions. 

Cast away the const qualifier in BBinder::findObject.  C11, unlike C++11,
does not allow loads from const atomics.  This is widely regarded as
a bug (see WG14 DR 459).  This is a hack to work around it until it's
officially fixed in the spec.

load_const_atomic was adapted from commit
1e8587a479fd8b1ce9b594298a93f517816e8f15

I don't think we want to dignify this by putting it into a header file.

Bug:17067219
Change-Id: Icbfcbda2722e6f80d2bb065a0bb3ec7634bcacb2
parent 7d587c31

libs/binder/Binder.cpp

+9 −1
Original line number Diff line number Diff line
@@ -160,10 +160,18 @@ void BBinder::attachObject( 
    e->mObjects.attach(objectID, object, cleanupCookie, func);

}



// The C11 standard doesn't allow atomic loads from const fields,

// though C++11 does.  Fudge it until standards get straightened out.

static inline uintptr_t load_const_atomic(const atomic_uintptr_t* p,

                                          memory_order mo) {

    atomic_uintptr_t* non_const_p = const_cast<atomic_uintptr_t*>(p);

    return atomic_load_explicit(non_const_p, mo);

}



void* BBinder::findObject(const void* objectID) const

{

    Extras* e = reinterpret_cast<Extras*>(

                    atomic_load_explicit(&mExtras, memory_order_acquire));

                    load_const_atomic(&mExtras, memory_order_acquire));

    if (!e) return NULL;



    AutoMutex _l(e->mLock);