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Re: main return value is helpfull?

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On 4/16/2017 2:41 PM, Keith Thompson wrote:
>
> Returning 0 does indicate success, but the standard doesn't guarantee
> that exit(1) will indicate failure.  It does on many systems, but in
> particular Open VMS uses odd results for success and even results for
> failure (with 0 denoting success as a special case).  That's why we have
> the macros EXIT_SUCCESS and EXIT_FAILURE.
>
> EXIT_SUCCESS is almost always defined as 0, but there's no requirement
> that EXIT_SUCCESS==0, as long as both values denote success.
>

The "as long as both values denote success" remark appears to be 
unnecessary in this case. The specification of 'exit' states the following:

"[...] If the value of status is zero or EXIT_SUCCESS, an 
implementation-defined form of the status successful termination is 
returned. If the value of status is EXIT_FAILURE, an 
implementation-defined form of the status unsuccessful termination is 
returned. [...]"

This basically says that such status values as '0', 'EXIT_SUCCESS' and 
'EXIT_FAILURE' are given special treatment. They are not necessarily 
passed to the host environment _directly_. They are _translated_ into 
the proper host-specific status values indicating "success" and  "failure".

In other words, conceptually, the host environment never sees the actual 
value of 'EXIT_SUCCESS'. It does not matter what (if anything) the value 
of 'EXIT_SUCCESS' means in host environment. It is only the 
implementation that sees the actual values of 'EXIT_SUCCESS'. And it 
guarantees that 'exit(EXIT_SUCCESS)' will return to the host a [possibly 
different] status code indicating "success".

If some host environment uses values of '-1' and '255' to indicate 
"failure" and "success", it still perfectly possible to have 
'EXIT_FAILURE' defined as '1' and 'EXIT_SUCCESS' defined as '0', as long 
as 'exit' remembers to translate '1' to '-1' and '0' to '255'.

-- 
Best regards,
Andrey Tarasevich

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main return value is helpfull? esmaeel ensanimehr <eensanimehr@gmail.com> - 2017-04-16 12:51 -0700
  Re: main return value is helpfull? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-16 21:11 +0100
  Re: main return value is helpfull? supercat@casperkitty.com - 2017-04-16 13:19 -0700
    Re: main return value is helpfull? Keith Thompson <kst-u@mib.org> - 2017-04-16 14:41 -0700
      Re: main return value is helpfull? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2017-04-16 18:58 -0700
    Re: main return value is helpfull? Manfred <noname@invalid.add> - 2017-04-17 19:34 +0200
    Re: main return value is helpfull? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2017-04-17 13:57 -0400
      Re: main return value is helpfull? Keith Thompson <kst-u@mib.org> - 2017-04-17 12:19 -0700
        Re: main return value is helpfull? Manfred <noname@invalid.add> - 2017-04-18 13:03 +0200
          Re: main return value is helpfull? Keith Thompson <kst-u@mib.org> - 2017-04-18 09:29 -0700
  Re: main return value is helpfull? gordonb.xo0e7@burditt.org (Gordon Burditt) - 2017-04-17 04:40 -0500
  Re: main return value is helpfull? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2017-04-18 21:39 -0600

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