Re: naked switches

From	Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups	comp.lang.c
Subject	Re: naked switches
Date	2021-07-11 00:57 -0700
Organization	A noiseless patient Spider
Message-ID	<861r858eqz.fsf@linuxsc.com> (permalink)
References	(2 earlier) <255c09e7-2365-4983-ad4d-3bfc83cf04e7n@googlegroups.com> <31342574-cb69-4ad6-8576-387dcf9caf70n@googlegroups.com> <sc76v8$8ah$1@dont-email.me> <7e094b82-01be-4d7f-9793-4eeda725ca0en@googlegroups.com> <20210708103653.702@kylheku.com>

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Kaz Kylheku <563-365-8930@kylheku.com> writes:

> On 2021-07-08, Robert Finch <robfi680@gmail.com> wrote:
>
>>> You wrote that you "have been working on a C/C++ like compiler" - do you
>>> mean you have been /using/ such a compiler, or you have been /writing/
>>> such a compiler?
>>
>> I have been using it for simple demos, actually running the compiled
>> code sometime.  It has been revamped for several different custom
>> processors, but is still a work in progress.
>>
>>> As I mentioned earlier, I think a "naked switch" like this is a terrible
>>> idea.  It is not something I have seen on other compilers, and I've used
>>> quite a large number over the years for far smaller and slower devices
>>> than you are describing here.
>>
>> It is a bad idea in terms of allowing program crashes.  But then
>> there are naked functions.
>>
>> CC64 supports a number of ?features?  not found in standard C. But I
>> call it a ?C?  like compiler because it can compile most C code
>> without changes.  I used it to compile the standard C library.
>> Stills lots of bugs in the compiler though.
>>
>> One feature I like is the ability to manipulate bit slices.
>>
>> int a, b;
>>
>> a = b[10:1];
>>
>> Sets a equal to bits 1 to 10 of b.  A bit slice can be distinguished
>> from an array index by the colon.  Compiles painlessly directly to
>> field manipulation instructions and gets rid of code like:  a = (b >>
>> 1) & 0x3ff;
>
> A macro can do this:
>
>  a = BIT(b,10,1);
>
> and works everywhere.  What you need is a typeof extension to make it
> work with different integer types while retaining efficiency, otherwise
> you're looking at making it assume 64 bit, or saddling it with a type
> name argument.  [... and later _Generic is mentioned.]

No typeof is needed, nor _Generic, nor type name argument, nor
forcing a width of 64 bits, to define a macro that produces an
"and" of the appropriate size with a compile-time constant (as
evidenced by both gcc and clang with -O0).  Just straight C90.

(I'll try to post a followup in a day or two, if necessary, to
show how.  But I expect someone here will get it before then.)

Thread

naked switches Robert Finch <robfi680@gmail.com> - 2021-07-07 16:39 -0700
  Re: naked switches Bart <bc@freeuk.com> - 2021-07-08 01:26 +0100
  Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-08 01:57 +0000
    Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-08 09:16 +0200
  Re: naked switches Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-08 01:00 -0700
    Re: naked switches Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2021-07-08 03:25 -0700
      Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-08 06:58 -0700
        Re: naked switches Bart <bc@freeuk.com> - 2021-07-08 15:52 +0100
        Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-08 17:52 +0200
          Re: naked switches Bart <bc@freeuk.com> - 2021-07-08 17:51 +0100
            Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 10:01 +0200
              Re: naked switches Bart <bc@freeuk.com> - 2021-07-09 11:09 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 13:14 +0200
                Re: naked switches Manfred <noname@add.invalid> - 2021-07-09 15:35 +0200
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 16:51 +0200
                Re: naked switches Manfred <noname@add.invalid> - 2021-07-09 18:23 +0200
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-09 16:07 +0100
                Re: naked switches Manfred <noname@add.invalid> - 2021-07-09 18:41 +0200
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-10 11:02 +0200
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 19:20 +0200
                Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-09 10:46 -0700
                Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-09 19:56 +0000
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-09 22:01 +0100
                Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-09 15:07 -0700
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-09 23:30 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-10 12:17 +0200
          Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-08 10:18 -0700
            Re: naked switches Bart <bc@freeuk.com> - 2021-07-08 18:43 +0100
              Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-08 15:32 -0700
            Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-08 17:47 +0000
              Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-08 15:45 -0700
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 10:27 +0200
                Re: naked switches Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-07-09 11:13 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 13:30 +0200
                Re: naked switches Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-11 00:39 -0700
                Re: naked switches scott@slp53.sl.home (Scott Lurndal) - 2021-07-11 14:06 +0000
                Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-07-11 08:01 -0700
                Re: naked switches Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-16 03:53 -0700
                Re: naked switches scott@slp53.sl.home (Scott Lurndal) - 2021-07-16 14:47 +0000
                Re: naked switches Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-09-30 06:09 -0700
                Re: naked switches Robert Finch <robfi680@gmail.com> - 2021-09-30 07:03 -0700
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-09 13:44 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-10 13:28 +0200
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-10 13:04 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-10 15:39 +0200
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-10 15:08 +0100
                Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-10 17:34 +0200
                Re: naked switches Bart <bc@freeuk.com> - 2021-07-10 17:47 +0100
              Re: naked switches Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-11 00:57 -0700
                Re: naked switches Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-16 03:51 -0700
        Re: naked switches Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-08 11:40 -0700
          Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 10:38 +0200
  Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-08 17:33 +0000
    Re: naked switches scott@slp53.sl.home (Scott Lurndal) - 2021-07-08 17:47 +0000
      Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-08 17:58 +0000
        Re: naked switches scott@slp53.sl.home (Scott Lurndal) - 2021-07-08 19:13 +0000
          Re: naked switches Kaz Kylheku <563-365-8930@kylheku.com> - 2021-07-09 02:30 +0000
        Re: naked switches David Brown <david.brown@hesbynett.no> - 2021-07-09 10:41 +0200
  Re: naked switches Bonita Montero <Bonita.Montero@gmail.com> - 2021-09-30 18:04 +0200

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