Path: utzoo!attcan!uunet!cs.utexas.edu!ut-emx!nowhere!sking
From: sking@nowhere.uucp (Steven King)
Newsgroups: comp.lang.c++
Subject: Re: operator++()   and   testing 'this'
Message-ID: <1990Oct14.224706.1934@nowhere.uucp>
Date: 14 Oct 90 22:47:06 GMT
Organization: nowhere
Lines: 34


In article <1990Oct9.144542.19983@sco.COM> jfischer@sco.COM (Jonathan A. Fischer) writes:
>In article <706@msor0.UUCP> kt@msor.UUCP (Keith Tizzard) writes:
>>Two questions about C++
>>
>>2   Testing of and assigning to 'this'
>>
>>Is it still possible to assign to 'this' in V2.0?
>
>	Technically, you can't assign to this, since it's "X * const this".
>BUT, it's listed in Appendix B.3.3 as an "anachronism," something that is
>provided for compatibility with earlier releases of cfront.  I.e., you can do
>it, but technically you shouldn't.  Also, there is no requirement for a
>compiler vendor to implement these anachronisms, so you are tainting your
>portability by using them.
>
>>Can one rely on 'this' having the value zero on entry to the constructor
>>if the object is allocated on the free store?
>
>	Yep, according to the same anachronisms section.

	And only if the object isnt a member (or base) of another object.
Even tho' the translator knows this information (it does pass a flag to
destructors) there is NOT a reliable mechanism to determine this from within
a constructor.

	I wonder if there is enough of a need for this to consider adding it
to the language...

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