Re: Is enum a suitable way to implement a "local define?"

From	glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: Is enum a suitable way to implement a "local define?"
Date	2014-04-15 05:26 +0000
Organization	Aioe.org NNTP Server
Message-ID	<liiftu$rok$1@speranza.aioe.org> (permalink)
References	(9 earlier) <li093i$svh$1@dont-email.me> <TJ_0v.147431$Bj3.3238@fx09.am4> <li24jo$22j$1@dont-email.me> <lnha63avgt.fsf@nuthaus.mib.org> <kfnha5vcip4.fsf@x-alumni2.alumni.caltech.edu>

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Tim Rentsch <txr@alumni.caltech.edu> wrote:
> Keith Thompson <kst-u@mib.org> writes:

>> "const" in C simply means "read-only".  "Constant" refers to
>> something that can (and must) be evaluated at compile time, as
>> in "integer constant" (what some languages call an "integer
>> literal") or a "constant expression" (an expression that can be
>> used as if it were a literal).

> Not exactly right.  An address constant is a form of constant
> expression, but it can't be evaluated at compile time.  It is
> evaluated before program execution begins but AFAIK it is not
> required to be fixed even after linking is done.  

I haven't heard the term "address constant" used so much outside
of S/360 (and successor) assembler programming. 

> That is, different runs of the same executable might 
> produce different values for an "address constant".  
>I'm pretty sure the Standard means for an address constant 
> to have any particular value only within a single execution 
> of a compiled and linked program, not necessarily for 
> all executions (of the same program image).

For S/360 address constants, which may or may not generalize to
other systems, they can be either absolute or relocatable. 
Absolute address constants don't change on relocation, and
relocatable ones do (maybe that is too obvious). 

Pointer constant sounds more C-like to me.

The assembler stores the offset into the CSECT, the linker
updates that as it relocates it within the load module, and
program fetch updates again as it is being loaded into memory.

To get back to C, some things are required to be known at compile
time, and so compile time constants. 

Among others, C doesn't require subtraction between pointers to
different objects to have a defined value. Subtracting two constant
pointers to different objects, then, should not be a compile time 
constant, even though the compilers for some systems could 
probably compute one. I presume C can compute a constant absolute
expression with pointers to the same object.

Another interesting feature of the OS/360 assembler that I haven't
known in others is that the relocation factor, in addition to the
usual 0 or 1, can also be -1 or 2. In C terms, you can compute 
the value of -pointer, 2*pointer, or pointer1+pointer2 as an
address constant. C doesn't allow for that.

-- glen

Thread

Is enum a suitable way to implement a "local define?" partremmaps@gmail.com - 2014-04-05 13:07 -0700
  Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-05 13:55 -0700
  Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-05 14:14 -0700
    Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-06 22:18 +0200
      Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-06 13:28 -0700
      Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-06 16:35 -0400
      Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 08:55 +1200
        Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-06 23:30 +0200
          Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 10:12 +1200
          Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-06 18:22 -0400
  Re: Is enum a suitable way to implement a "local define?" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-05 14:30 -0700
  Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-05 22:39 +0100
    Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-06 22:27 +0200
      Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 08:52 +1200
      Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-06 23:20 +0100
        Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 02:17 +0200
          Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-06 19:00 -0700
            Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-07 04:44 +0000
              Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 10:15 +0100
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-07 18:32 +0000
                Re: Is enum a suitable way to implement a "local define?" Kaz Kylheku <kaz@kylheku.com> - 2014-04-07 18:47 +0000
              Re: Is enum a suitable way to implement a "local define?" Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-04-07 11:39 +0200
            Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 08:58 +0200
              Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 19:34 +1200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 09:41 +0100
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 21:45 +1200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 11:03 +0100
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 12:54 +0200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 13:48 +0100
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 15:27 +0200
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-07 23:00 +1200
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 11:31 +0200
                Re: Is enum a suitable way to implement a "local define?" Les Cargill <lcargill99@comcast.com> - 2014-04-07 07:24 -0500
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 15:02 +0200
          Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 10:19 +0100
            Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 12:43 +0200
              Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 13:27 +0100
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 15:16 +0200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 14:43 +0100
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 16:44 +0200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 16:52 +0100
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-07 12:53 -0400
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-07 12:59 -0400
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 18:12 +0100
                Re: Is enum a suitable way to implement a "local define?" Richard <rgrdev_@gmail.com> - 2014-04-07 18:27 +0100
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-08 23:22 +0100
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-08 18:44 -0400
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-09 00:22 +0100
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-08 09:39 +0200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-08 23:27 +0100
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-09 10:52 +1200
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-09 00:24 +0100
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-09 11:32 +1200
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-09 08:58 +0200
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-08 19:54 -0400
                Re: Is enum a suitable way to implement a "local define?" Kaz Kylheku <kaz@kylheku.com> - 2014-04-09 00:41 +0000
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-08 23:05 +0000
                Re: Is enum a suitable way to implement a "local define?" Stephen Sprunk <stephen@sprunk.org> - 2014-04-08 18:24 -0500
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-08 19:39 -0400
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-08 22:41 -0700
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-09 09:16 +0200
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-09 07:27 -0400
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-09 15:32 +0200
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-09 08:32 -0700
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-10 11:03 +0200
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 07:27 -0400
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-10 14:02 +0200
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-10 08:34 -0700
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-10 16:36 +0000
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 12:58 -0400
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-09 11:36 -0400
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-09 18:36 +0000
                Re: Is enum a suitable way to implement a "local define?" Stephen Sprunk <stephen@sprunk.org> - 2014-04-09 14:11 -0500
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-10 13:55 +0200
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-09 02:35 +0200
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-08 23:05 -0700
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-09 09:45 +0200
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-09 08:19 -0700
                Re: Is enum a suitable way to implement a "local define?" Richard <rgrdev_@gmail.com> - 2014-04-10 09:08 +0100
                Re: Is enum a suitable way to implement a "local define?" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-10 02:57 -0700
                Re: Is enum a suitable way to implement a "local define?" Richard <rgrdev_@gmail.com> - 2014-04-10 11:50 +0100
                Re: Is enum a suitable way to implement a "local define?" Seungbeom Kim <musiphil@bawi.org> - 2014-04-10 11:37 -0700
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 14:52 -0400
                Re: Is enum a suitable way to implement a "local define?" Kaz Kylheku <kaz@kylheku.com> - 2014-04-10 18:53 +0000
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-10 19:36 +0000
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 15:59 -0400
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-10 20:12 +0000
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 16:18 -0400
                Re: Is enum a suitable way to implement a "local define?" Martin Shobe <martin.shobe@yahoo.com> - 2014-04-11 10:24 -0500
                Re: Is enum a suitable way to implement a "local define?" Martin Shobe <martin.shobe@yahoo.com> - 2014-04-11 14:36 -0500
                Re: Is enum a suitable way to implement a "local define?" David Thompson <dave.thompson2@verizon.net> - 2014-05-25 16:44 -0400
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-10 12:47 -0700
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 16:05 -0400
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-10 13:34 -0700
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-10 16:59 -0400
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-10 16:01 -0700
                Re: Is enum a suitable way to implement a "local define?" Tim Rentsch <txr@alumni.caltech.edu> - 2014-04-14 21:24 -0700
                Re: Is enum a suitable way to implement a "local define?" Tim Rentsch <txr@alumni.caltech.edu> - 2014-04-14 21:36 -0700
                Re: Is enum a suitable way to implement a "local define?" glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-15 05:26 +0000
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-15 07:18 -0400
                Re: Is enum a suitable way to implement a "local define?" Tim Rentsch <txr@alumni.caltech.edu> - 2014-04-18 09:01 -0700
                Please ignore trolls Noob <root@127.0.0.1> - 2014-04-09 15:26 +0200
                Re: Please ignore trolls David Brown <david.brown@hesbynett.no> - 2014-04-09 15:38 +0200
                Re: Please ignore trolls James Kuyper <jameskuyper@verizon.net> - 2014-04-09 12:02 -0400
                Re: Please ignore trolls Kaz Kylheku <kaz@kylheku.com> - 2014-04-09 19:18 +0000
                Re: Please ignore trolls "BartC" <bc@freeuk.com> - 2014-04-10 20:18 +0100
                Re: Please ignore trolls James Kuyper <jameskuyper@verizon.net> - 2014-04-10 15:49 -0400
                Re: Please ignore trolls gazelle@shell.xmission.com (Kenny McCormack) - 2014-04-10 20:14 +0000
                Re: Please ignore trolls "BartC" <bc@freeuk.com> - 2014-04-11 14:35 +0100
                Re: Please ignore trolls Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-11 07:35 -0700
                Re: Please ignore trolls "BartC" <bc@freeuk.com> - 2014-04-11 15:51 +0100
                Re: Please ignore trolls Jorgen Grahn <grahn+nntp@snipabacken.se> - 2014-04-12 15:48 +0000
                Re: Please ignore trolls Kaz Kylheku <kaz@kylheku.com> - 2014-04-10 21:16 +0000
                Re: Please ignore trolls "BartC" <bc@freeuk.com> - 2014-04-12 15:35 +0100
                Re: Please ignore trolls Keith Thompson <kst-u@mib.org> - 2014-04-09 08:03 -0700
                Re: Please ignore trolls gazelle@shell.xmission.com (Kenny McCormack) - 2014-04-09 15:25 +0000
                Re: Is enum a suitable way to implement a "local define?" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-04-09 21:28 +0100
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-10 08:39 +1200
                Re: Is enum a suitable way to implement a "local define?" Kaz Kylheku <kaz@kylheku.com> - 2014-04-09 23:38 +0000
                Re: Is enum a suitable way to implement a "local define?" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-04-10 02:07 +0100
                Re: Is enum a suitable way to implement a "local define?" Ike Naar <ike@iceland.freeshell.org> - 2014-04-09 05:18 +0000
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-09 08:05 -0700
            Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-07 08:33 -0700
              Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-07 17:16 +0100
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-07 11:07 -0700
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-08 09:49 +0200
                Re: Is enum a suitable way to implement a "local define?" Ian Collins <ian-news@hotmail.com> - 2014-04-08 20:33 +1200
                Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-08 12:31 +0200
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-08 21:59 -0400
                Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-08 07:37 -0700
              Re: Is enum a suitable way to implement a "local define?" Stephen Sprunk <stephen@sprunk.org> - 2014-04-08 08:35 -0500
                Re: Is enum a suitable way to implement a "local define?" Seungbeom Kim <musiphil@bawi.org> - 2014-04-08 11:30 -0700
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-08 23:46 +0100
                Re: Is enum a suitable way to implement a "local define?" Stephen Sprunk <stephen@sprunk.org> - 2014-04-08 18:28 -0500
                Re: Is enum a suitable way to implement a "local define?" Seungbeom Kim <musiphil@bawi.org> - 2014-04-08 17:21 -0700
                Re: Is enum a suitable way to implement a "local define?" "BartC" <bc@freeuk.com> - 2014-04-09 09:07 +0100
                Re: Is enum a suitable way to implement a "local define?" James Kuyper <jameskuyper@verizon.net> - 2014-04-09 07:22 -0400
      Re: Is enum a suitable way to implement a "local define?" Keith Thompson <kst-u@mib.org> - 2014-04-06 16:25 -0700
        Re: Is enum a suitable way to implement a "local define?" David Brown <david.brown@hesbynett.no> - 2014-04-07 02:22 +0200
  Re: Is enum a suitable way to implement a "local define?" Ike Naar <ike@iceland.freeshell.org> - 2014-04-06 06:08 +0000
  Re: Is enum a suitable way to implement a "local define?" jacob navia <jacob@spamsink.net> - 2014-04-06 08:54 +0200
  Re: Is enum a suitable way to implement a "local define?" partremmaps@gmail.com - 2014-04-07 23:48 -0700

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