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Groups > comp.lang.c > #140151

Re: Compiler tests

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Compiler tests
Date 2019-01-24 11:41 +0100
Organization A noiseless patient Spider
Message-ID <q2c4p0$6i3$1@dont-email.me> (permalink)
References (17 earlier) <9h02E.76962$XD2.32484@fx10.am4> <q2a438$aj2$1@dont-email.me> <87o987xgxl.fsf@bsb.me.uk> <q2alb9$sg7$1@dont-email.me> <87imyfxcnu.fsf@bsb.me.uk>

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On 23/01/2019 22:54, Ben Bacarisse wrote:
> David Brown <david.brown@hesbynett.no> writes:
> 
>> On 23/01/2019 21:22, Ben Bacarisse wrote:
>>> David Brown <david.brown@hesbynett.no> writes:
>>>
>>>> On 23/01/2019 17:05, Bart wrote:
>>> <snip>
>>>>> There is a problem with finding a general way of translating named
>>>>> constants in one language to the equivalent in C, where it is necessary
>>>>> to choose between #define, or enums or just showing the literal directly.
>>>>
>>>> There is only a problem because you make it a problem - and you only do
>>>> that so that you can claim that C has a problem with constants.
>>>
>>> Bart has a point here.  C /does/ have a problem with "named
>>> constants" -- what would be thought of in other languages as names
>>> denoting values.  In C, most names denotes objects.  enum members can
>>> name integer values, but that's about it.
>>
>> C certainly could be improved regarding constants (C++ has done
>> so). That is different from saying it has a problem.
> 
> I don't want to get into an argument about words like "problem".  C has
> almost no way to name a value, and that appears to be fine for most
> people so maybe there is no "problem".
> 

Fair enough.

>> There are few
>> uses of named constants that you can't make work in C reasonably
>> easily (as long as you are not allergic to #define).
> 
> #define just won't cut it.  It names a code construct not a value and
> that can lead to all sorts of problems.  As C programmers, I think we
> just forget about the problems.  When
> 
>   #define USABLE_BYTES 1024
> 
> has to turn into
> 
>   #define USABLE_BYTES (calc_bytes_avalable(fp))
> 
> we either accept the multiple calls or switch to a "const variable".
> It's just the cost of doing business in C, just like the other
> work-arounds you hint at in your reply.
> 
>> C++ style const
>> and constexpr give you more.
> 
> I am not sure what your point is here.  Lots of languages give you
> more.  Some even have a uniform way to name values!  C++ is hardly to be
> held up as one that's fixed all this.
> 

C++ has its history as an extension to C, and retains C as an almost
complete subset.  Thus it shows some ideas of what could be done to make
constants better in C.  It is also an option if you want to program
basically in C, but with better constants.  Other languages may have
better ways of handling named constants, but they are further from C.

>>> But Bart has also made a problem for himself because he's translating
>>> into C, not compiling to C.  I think he's often trying to find matching
>>> constructs rather than simply generating code that has the required
>>> semantics.
>>
>> Agreed.  That is a good summary.
>>
>>>
>>>> Floating constants will only be used as floating point numbers.  You can
>>>> translate them to "static const double pie = 1.234;" without trouble.
>>>
>>> Not when the value is the result of what C views as a non-constant
>>> expression.  OK, so in that case you can just drop the static, but it's
>>> not as simple as you suggest in general.
>>
>> But he is generating the C code.  Surely such expressions should be
>> calculated by his translator, using the source language's semantics
>> (which could involve different precisions, rounding, etc.) and then
>> write the literal value directly to the C code.  Maybe that is the
>> translator/compiler issue you mentioned.
> 
> In Algol 68 (one of the first languages to get this right)
> 
>   INT x = f(y);
> 
> calls f at run-time (optimisations aside) and names the resulting value
> x.  You can't take the address of x because it's has no storage (again
> "as if rules" aside), and you can't alter x because it is not a
> variable.
> 

I don't see how that differs from C++ :

	const int x = f(y);

You /can/ take the address of x, but that doesn't matter.  If the
calculations for f(y) and the use of x are such that storage is not
needed, storage will not be used.  If storage is needed, it /will/ be
used.  And in Algol, I assume the same applies.

C won't let you do this outside a function, which is a limitation.

> But the key point is that you can't translate that into C by running f
> at compile time.
> 
>> Perhaps he would be better translating to C++.  I think more of his
>> concepts would work there.
> 
> If he compiled into C it would not matter.  You would turn the above
> into
> 
>   int_type v435 = f(v356);
> 
> with no need for const (to stop assignments) or register (to prevent
> address taking) because the source language compiler would be doing
> those checks.  He would not have to match the construct in any way.
> 

Agreed.

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Compiler tests Bart <bc@freeuk.com> - 2019-01-20 00:03 +0000
  Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-20 16:52 +1300
    Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-20 10:27 +0100
      Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 12:37 +0100
        Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 13:08 +0000
          Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 15:02 +0000
            Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 17:31 +0100
              Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 17:08 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 21:40 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 22:41 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 00:39 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 00:36 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-21 16:33 +1300
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 11:58 +0000
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 04:15 -0800
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-22 07:53 +1300
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 01:15 -0600
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 12:00 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-24 08:13 +1300
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 13:30 -0600
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 08:22 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 12:23 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 14:42 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 14:17 +0000
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 12:46 -0800
                You guys really, really need to get a room (Was: Compiler tests) gazelle@shell.xmission.com (Kenny McCormack) - 2019-01-24 14:05 +0000
          Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-20 17:27 +0100
            Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 17:19 +0000
              Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 09:44 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 12:49 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 15:31 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-21 14:38 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-21 15:15 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-21 16:05 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 16:39 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-21 12:51 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 00:16 +0000
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-22 08:43 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:31 +0000
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-22 17:49 +0100
                Re: Compiler tests jacobnavia <jacob@jacob.remcomp.fr> - 2019-01-23 11:04 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 11:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-21 15:35 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-21 15:49 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-21 17:42 +0100
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 03:18 -0600
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 11:11 +0100
                Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-23 12:18 -0600
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 13:56 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 10:55 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:07 +0000
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 04:29 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 12:52 +0000
                Re: Compiler tests mark.bluemel@gmail.com - 2019-01-22 05:04 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:18 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:45 -0800
                Re: Compiler tests fir <profesor.fir@gmail.com> - 2019-01-22 05:35 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 15:10 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 17:30 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-22 23:02 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-22 23:14 +0000
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 15:45 -0800
                Re: Compiler tests Robert Wessel <robertwessel2@yahoo.com> - 2019-01-22 17:57 -0600
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 16:36 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 01:37 +0000
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-22 18:53 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 09:42 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 09:22 +0100
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 08:52 -0500
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 15:13 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 14:33 +0000
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 07:30 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:05 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 17:17 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:29 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 22:04 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 21:50 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 10:45 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 11:55 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 13:58 +0100
                Re: Compiler tests mark.bluemel@gmail.com - 2019-01-24 05:07 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 14:10 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 14:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 15:51 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 15:44 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 17:32 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-24 19:07 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 20:14 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 22:24 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-24 22:46 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-25 12:34 +1300
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 01:01 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-25 14:15 +1300
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 10:05 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:51 +0000
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 09:48 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 10:56 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 12:08 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 13:28 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 13:33 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:38 +0100
                Re: Compiler tests Mateusz Viste <mateusz@wont.tell> - 2019-01-25 15:08 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 13:53 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 12:25 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 10:03 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 10:08 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 11:14 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 12:02 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 13:37 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 13:58 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:26 +0100
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 15:01 +0100
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:42 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 10:25 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:37 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 16:33 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:44 -0800
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 17:53 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 10:33 -0800
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 20:43 +0100
                Re: Compiler tests Keith Thompson <kst-u@mib.org> - 2019-01-25 12:17 -0800
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 18:31 +0000
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 20:41 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 21:19 +0000
                Re: Compiler tests Ian Collins <ian-news@hotmail.com> - 2019-01-26 10:24 +1300
                Re: Compiler tests "Pascal J. Bourguignon" <pjb@informatimago.com> - 2019-01-25 22:27 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 22:39 +0000
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 18:46 +0000
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 12:43 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:37 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 14:19 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 15:47 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-25 07:17 -0800
                Re: Compiler tests Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-02-03 07:28 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-02-03 12:35 +0100
                Re: Compiler tests Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-02-03 21:47 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-02-03 22:57 +0100
                Re: Compiler tests Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-01-24 06:47 -0800
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-23 20:22 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 22:12 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-23 21:54 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-24 11:41 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-24 23:17 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 11:11 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 12:04 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 14:05 +0100
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 18:40 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-25 22:36 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-25 22:15 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-25 14:48 +0000
                Re: Compiler tests scott@slp53.sl.home (Scott Lurndal) - 2019-01-25 14:46 +0000
                Re: Compiler tests Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-01-25 17:48 +0000
                Re: Compiler tests James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-23 08:23 -0800
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 16:41 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 16:18 +0000
                Re: Compiler tests David Brown <david.brown@hesbynett.no> - 2019-01-23 17:28 +0100
                Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-23 20:23 +0000
                Re: Compiler tests Robert Wessel <robertwessel2@yahoo.com> - 2019-01-22 17:52 -0600
          Re: Compiler tests Bart <bc@freeuk.com> - 2019-01-20 20:17 +0000
    Re: Compiler tests BGB <cr88192@hotmail.com> - 2019-01-21 00:13 -0600

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