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Groups > comp.lang.c > #104370

Re: modifying local const variable run time

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: modifying local const variable run time
Date 2017-02-22 16:31 +0100
Organization A noiseless patient Spider
Message-ID <o8kaog$9cc$2@dont-email.me> (permalink)
References <c5e88b2a-20a5-4083-a40a-a17d57aa42f7@googlegroups.com> <20170222160611.91c1f3085d6c9e3571a68156@gmail.com> <3cba5f3c-735a-45b7-87f2-d03dd8a18720@googlegroups.com>

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On 22/02/17 16:26, rahul.dev.agg@gmail.com wrote:
> On Wednesday, February 22, 2017 at 8:38:13 PM UTC+5:30, GOTHIER Nathan wrote:
>> On Wed, 22 Feb 2017 06:39:51 -0800 (PST)
>> rahul.dev.agg@gmail.com wrote:
>>
>>> int func(void)
>>> {
>>>    const int i = getc();
>>>
>>> }
>>>
>>> Is this correct ? Can we modify const local variable run time ?
>>
>> It should be correct if you don't try to assign a value to your constant
>> integer. Constant objects should only be initialized.
> 
> But, how this would be implemented ?
> I read that const variable can be stored in read only memory.
> In that case, it's value should be known at compile time.
> Or is there I am missing something ?
> 

A compiler /may/ put a const object in read-only memory, if it knows the
initialisation value when the program is compiled.  It can't do that for
const objects that are initialised at run time.  Think of your code here
as a saying "I want an "int" called "i", initialised to the result of a
call to getc(), and it will not be changed after initialisation".

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Thread

modifying local const variable run time rahul.dev.agg@gmail.com - 2017-02-22 06:39 -0800
  Re: modifying local const variable run time GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-02-22 16:06 +0100
    Re: modifying local const variable run time rahul.dev.agg@gmail.com - 2017-02-22 07:26 -0800
      Re: modifying local const variable run time David Brown <david.brown@hesbynett.no> - 2017-02-22 16:31 +0100
        Re: modifying local const variable run time rahul.dev.agg@gmail.com - 2017-02-22 07:43 -0800
          Re: modifying local const variable run time Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-22 16:06 +0000
      Re: modifying local const variable run time James Kuyper <jameskuyper@verizon.net> - 2017-02-22 11:13 -0500
      Re: modifying local const variable run time supercat@casperkitty.com - 2017-02-22 08:34 -0800
        Re: modifying local const variable run time David Brown <david.brown@hesbynett.no> - 2017-02-22 23:03 +0100
      Re: modifying local const variable run time GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-02-22 17:34 +0100
        Re: modifying local const variable run time Robert Wessel <robertwessel2@yahoo.com> - 2017-02-22 10:52 -0600
          Re: modifying local const variable run time GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-02-22 17:52 +0100
            Re: modifying local const variable run time Keith Thompson <kst-u@mib.org> - 2017-02-22 09:33 -0800
            Re: modifying local const variable run time James Kuyper <jameskuyper@verizon.net> - 2017-02-22 15:50 -0500
              Re: modifying local const variable run time supercat@casperkitty.com - 2017-02-22 13:13 -0800
                Re: modifying local const variable run time Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-22 21:55 +0000
                Re: modifying local const variable run time supercat@casperkitty.com - 2017-02-22 14:43 -0800
        Re: modifying local const variable run time Keith Thompson <kst-u@mib.org> - 2017-02-22 09:23 -0800
          Re: modifying local const variable run time GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-02-22 18:32 +0100
            Re: modifying local const variable run time Keith Thompson <kst-u@mib.org> - 2017-02-22 09:50 -0800
              Re: modifying local const variable run time David Brown <david.brown@hesbynett.no> - 2017-02-22 23:07 +0100
                Re: modifying local const variable run time Keith Thompson <kst-u@mib.org> - 2017-02-22 15:20 -0800
                Re: modifying local const variable run time David Brown <david.brown@hesbynett.no> - 2017-02-23 09:50 +0100
  Re: modifying local const variable run time James Kuyper <jameskuyper@verizon.net> - 2017-02-22 10:16 -0500
  Re: modifying local const variable run time Keith Thompson <kst-u@mib.org> - 2017-02-22 09:17 -0800

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