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From: ttwang@polyslo.CalPoly.EDU (Thomas Wang)
Newsgroups: comp.arch
Subject: Re: Parity hardware for uninitialized variable checking?
Message-ID: <14206@polyslo.CalPoly.EDU>
Date: 4 Sep 89 07:07:38 GMT
References: <14166@polyslo.CalPoly.EDU> <28784@news.Think.COM>
Reply-To: ttwang@polyslo.CalPoly.EDU (Thomas Wang)
Distribution: usa
Organization: Cal Poly State University -- San Luis Obispo
Lines: 41

barmar@think.COM (Barry Margolin) writes:
>Runtime error detection slows down programs when done only in
>software.  That's why language designers would like hardware
>facilities to support it.

One should not need to do software check on uninitialized variables.  The
language can be designed so uninitialized variables are impossible
to create.

>Just because a variable is initialized doesn't mean it has a *useful*
>value.  C automatically initializes all statics to 0, but that might
>not be a valid value as far as the application is concerned.

You should be able to specify a default initialization value, or even to
explicitly forbid the creation of variables with default value.

>In article <14166@polyslo.CalPoly.EDU> ttwang@polyslo.CalPoly.EDU (Thomas Wang) writes:
>>Yes.  Insist you initialize a variable when you create it.

>What if you don't know what value it should have yet?

You can create the variable with a default value, or delay the creation of
the variable until you know what value it should have.

main()
{
  type_car my_car; /* create a car with default 4 doors */
}

main()
{
  int door_number = get_number_of_doors(stdin);
  some_stuff();
  type_car my_car(door_number); /* create a car with # doors specified */
}

>Barry Margolin

 -Thomas Wang (Ah so desu ka!)

                                                     ttwang@polyslo.calpoly.edu