Where is the implementation of InternalEquals(object objA, object objB)

Question

While disassembling the .Net Source Code using Reflector, I came upon the Equals implementation in the Object Class and it refers to

bool InternalEquals(obj         


        

Answer 1

First, find in sscli20\clr\src\vm\ecall.cpp function mapping ("InternalEquals" -> ObjectNative::Equals):

FCFuncStart(gObjectFuncs)
    FCIntrinsic("GetType", ObjectNative::GetClass, CORINFO_INTRINSIC_Object_GetType)
    FCFuncElement("InternalGetHashCode", ObjectNative::GetHashCode)
    FCFuncElement("InternalEquals", ObjectNative::Equals)
    FCFuncElement("MemberwiseClone", ObjectNative::Clone)
FCFuncEnd()

Next, find an implementation ObjectNative::Equals (published by Mehrdad Afshari)

Answer 2

It's declared as [MethodImpl(MethodImplOptions.InternalCall)]. It means that it's implemented in the CLR itself, as a native procedure, not a .NET assembly.

You can view a similar CLR source code by looking at Microsoft SSCLI (aka Rotor).

In SSCLI 2.0 it's implemented as (in sscli20/clr/src/vm/comobject.cpp):

FCIMPL2(FC_BOOL_RET, ObjectNative::Equals, Object *pThisRef, Object *pCompareRef)
{
    CONTRACTL
    {
        THROWS;
        DISABLED(GC_NOTRIGGER);
        INJECT_FAULT(FCThrow(kOutOfMemoryException););
        MODE_COOPERATIVE;
        SO_TOLERANT;          
    }
    CONTRACTL_END;

    if (pThisRef == pCompareRef)    
        FC_RETURN_BOOL(TRUE);

    // Since we are in FCALL, we must handle NULL specially.
    if (pThisRef == NULL || pCompareRef == NULL)
         FC_RETURN_BOOL(FALSE);

    MethodTable *pThisMT = pThisRef->GetMethodTable();

    // If it's not a value class, don't compare by value
    if (!pThisMT->IsValueClass())
         FC_RETURN_BOOL(FALSE);

    // Make sure they are the same type.
    if (pThisMT != pCompareRef->GetMethodTable())
        FC_RETURN_BOOL(FALSE);

    // Compare the contents (size - vtable - sink block index).
    BOOL ret = memcmp(
        (void *) (pThisRef+1), 
        (void *) (pCompareRef+1), 
        pThisRef->GetMethodTable()->GetBaseSize() - sizeof(Object) - sizeof(int)) == 0;

    FC_GC_POLL_RET();

    FC_RETURN_BOOL(ret);
}
FCIMPLEND