From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Finding out parameters which are not written
Date: 1997/08/12
Date: 1997-08-12T00:00:00+00:00 [thread overview]
Message-ID: <EEtC87.9CC@world.std.com> (raw)
In-Reply-To: 33F07EA1.51D1@aut.alcatel.at
In article <33F07EA1.51D1@aut.alcatel.at>,
Gerhard Radatz <gerhard.radatz@aut.alcatel.at> wrote:
>Gerhard Radatz wrote:
>>
>> Does anyone know about a tool which can detect such situations as the
>> following:
>>
>> procedure xxx (result: out INTEGER) is
>> begin
>> if <<condition>> then
>> result := 0;
>> end if;
>> end;
>>
>> Obviously, this proc is erroneous and result will not be written if
>> <<condition>> is FALSE.
>I admit that it is very difficult to find such potential problems at
>compile time. ...
It doesn't seem so hard to me. The compiler can just check whether
every path through the function assigns to every 'out' parameter of a
scalar type. If not, warn -- it's almost certainly a bug. (For
composite types, it's not formally erroneous, and not necessarily a
bug.) There's no practical reason to worry about the fact that
<<condition>> might be always True (which of course the compiler can't
know, in general).
GNAT does exactly this sort of analysis for function returns -- it makes
sure that every path through the function ends with a return statement,
or the raise of an exception (and it has some mechanism for marking
procedures that always raise an exception). I don't know if GNAT does
something similar for scalar 'out' parameters, but it could.
Of course, none of this solves the more general problem of uninitialized
objects -- that really requires run-time checks.
- Bob
next prev parent reply other threads:[~1997-08-12 0:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-08-12 0:00 Finding out parameters which are not written Gerhard Radatz
1997-08-12 0:00 ` Gerhard Radatz
1997-08-12 0:00 ` Robert A Duff [this message]
1997-08-12 0:00 ` Matthew Heaney
1997-08-12 0:00 ` Larry Kilgallen
1997-08-17 0:00 ` Fergus Henderson
[not found] ` <5u180q$l69@mulga.cs.mu.OZ.AU>
1997-08-28 0:00 ` Stuart Palin
-- strict thread matches above, loose matches on Subject: below --
1997-08-27 0:00 Robert Dewar
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