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From: Florian Weimer <fw@deneb.enyo.de>
Newsgroups: comp.lang.ada
Subject: Re: A suggestion for resource management
Date: Sat, 21 Aug 2010 21:47:05 +0200
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Date: 2010-08-21T21:47:05+02:00
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* Dmitry A. Kazakov:

> On Sat, 21 Aug 2010 18:20:29 +0200, Florian Weimer wrote:
>
>>           procedure Test_External_Formats is
>>              ...
>>              COBOL_File : File_Type;
>>              ...
>> 
>>           begin
>>              Open (COBOL_File, Name => "Some_File");
>>              pragma Scoped (Close (COBOL_File));
>> 
>>              loop
>>                ...
>>           exception
>>              when End_Error => ...
>>           end Test_External_Formats;
>
> What is wrong with having a destructor for File_Type? If the language is to
> be extended why not to fix that first?

You can't always change libraries in that way.  Adding destructors has
both syntactic and run-time overhead.  The run-time overhead can be
minimized by a sufficiently advanced compiler (perhaps relying on
whole-program optimization to detect the lack of task aborts).  I'm
more concerned with the syntactic overhead.

There are some cases where the destructor solution doesn't really
apply.  For instance, the cleanup operation might need two parameters,
one denoting the object, and a second one decribing where to put it.