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From: Dmitry A. Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Modes (was unbounded_string)
Date: Mon, 13 Oct 2003 11:28:48 +0200
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Date: 2003-10-13T11:28:48+02:00
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On 11 Oct 2003 08:16:39 +0100, Simon Wright <simon@pushface.org>
wrote:

>Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> writes:
>
>> declare  -- I need the value of QUERY_STRING here
>>    Temp : String renames Getenv ("QUERY_STRING").all;
>>       -- Temp is an alias to the env-string. You cannot modify it.
>>       -- Yet it is not a pointer. An analogue would be C++ reference
>> begin
>>    ... -- Doing with Temp everything I can to do to
>>        -- a constant String
>> end; -- I don't need it anymore
>
>Actually you *can* modify it:
>
>   with Ada.Text_IO; use Ada.Text_IO;
>   with GNAT.OS_Lib; use GNAT.OS_Lib;
>
>   procedure Env is
>      Temp : String renames Getenv ("COLDFRAME").all;
>   begin
>      Temp (1) := 'x';
>      Put_Line (Temp);
>   end Env;
>
>then
>
>   smaug.pushface.org[5]$ COLDFRAME=foo ./env
>   xoo
>
>(GNAT 3.16a1)
>
>Should GNAT.OS_Lib.Getenv have been defined as returning a constant
>string access?
>
>   type Constant_String_Access is access constant String;

No, if Jeffrey Carter (see his post) is right and the result is
presently allocated on the heap, then it is a very bad design.

Clearly Getenv should either return an Unbounded_String or a plain
String.

---
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de