[openbeos-midi] Re: BMidiEndPoint

  • From: "Marcus Overhagen" <ml@xxxxxxxxxxxx>
  • To: openbeos-midi@xxxxxxxxxxxxx
  • Date: Thu, 10 Oct 2002 17:44:06 CEST (+0200)

Michael Pfeiffer wrote:

> For an implementation with atomic=5Fadd see "class Object" in
> BeUtils.h in directory current/src/servers/print:
> http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/open-beos/current/src/servers/print/BeUtils.h=3Frev=3D1.2&content-type=3Dtext/vnd.viewcvs-markup

That implementation is NOT correct. You do a non-atomic read of the fRefCount 
variable.

        bool Release() { 
                atomic=5Fadd(&fRefCount, -1); 
                if (fRefCount =3D=3D 0) { 
                        delete this; return true; 
                } else { 
                        return false; 
                } 
        }

But atomic=5Fadd returnes the value the variable had before the addition.
You can test for that value instead
The correct way would be:

        bool Release() { 
                if (1 =3D=3D atomic=5Fadd(&fRefCount, -1)) {
                        delete this; return true; 
                } else { 
                        return false; 
                } 
        }

Marcus


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