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Re: pure c on smartphones (and other devices)

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supercat@casperkitty.com wrote:
> On Sunday, October 4, 2015 at 7:54:12 AM UTC-5, fir wrote:
>> imo it was realy big mistake to expose only java code for user coders
 
> If a Java virtual machine is properly implemented, it will be possible for
> the system to accept and run untrusted Java code in a sandbox [in practice,
> many JVM implementations have security bugs].  Unless a C implementation
> produces some for of intermediate code for a VM, it will be very difficult
> for it to offer any significant security beyond what the OS can enforce,
> and I don't think Linux was designed with the intention of providing robust
> sandboxing.
 
> That having been said, I don't think it would be possible to write a C to
> bytecode compiler which would efficiently support the semantics that
> people expect from C code; it would need to either use four byte values to
> store each 32-bit value, or process byte loads and stores by continually
> packing and unpacking things stored in 32-bit values.  The best performance
> might come from having every group of four pointer-accessible bytes be
> represented by five members of a "byte[]" and one member of an "int[]",
> and using one byte to indicate whether:

I would be interested to see one where:

float *f;
f=malloc(100*sizeof(*f));
f[3]=3;

use JVM float and float array operations, and

int *p;
p=malloc(100*sizeof(*p));
p[3]=3;

used JVM int operations.

It gets more interesting if you:

memcpy(p, f, 100*sizeof(*f));

but it isn't hard for memcpy() to figure out the type
of its arguments and copy appropriately.

int *p;
p=malloc(100*sizeof(*f));
f=(float *) p;
f[3]=3;

is the case that really gets hard. 

but most C programs don't do that.
 
> 1. The corresponding int[] item and byte[] items held identical data.
> 2. The int[] value was written last.
> 3. The byte[] values were written last.
 
> Not terribly performant, but probably workable.  If C code could tolerate
> having "char" be 32 bits, that would simplify things a lot, but would of
> course break compatibility with a lot of code.

Java char is 16 bits, so you are halfway there.

-- glen

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pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-03 08:32 -0700
  pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 09:19 -0700
    Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-03 09:58 -0700
      Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 10:20 -0700
        Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-03 10:34 -0700
          Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 10:40 -0700
            Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-03 11:30 -0700
              Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-03 11:43 -0700
      Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 10:24 -0700
        Re: pure c on smartphones (and other devices) Johann Klammer <klammerj@NOSPAM.a1.net> - 2015-10-03 20:18 +0200
          Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-03 11:23 -0700
  Re: pure c on smartphones (and other devices) Aleksandar Kuktin <akuktin@gmail.com> - 2015-10-04 12:31 +0000
    Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-04 05:45 -0700
      Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-04 05:53 -0700
        Re: pure c on smartphones (and other devices) supercat@casperkitty.com - 2015-10-05 10:52 -0700
          Re: pure c on smartphones (and other devices) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-05 22:18 +0000
            Re: pure c on smartphones (and other devices) supercat@casperkitty.com - 2015-10-05 16:16 -0700
              Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-06 00:27 +0100
                Re: pure c on smartphones (and other devices) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-06 10:50 +0100
                Re: pure c on smartphones (and other devices) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 10:47 +0000
                Re: pure c on smartphones (and other devices) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-06 12:31 +0100
                Re: pure c on smartphones (and other devices) supercat@casperkitty.com - 2015-10-06 09:18 -0700
                Re: pure c on smartphones (and other devices) Rosario19 <Ros@invalid.invalid> - 2015-10-06 18:30 +0200
                Re: pure c on smartphones (and other devices) supercat@casperkitty.com - 2015-10-06 10:14 -0700
                Re: pure c on smartphones (and other devices) Waldek Hebisch <antispam@math.uni.wroc.pl> - 2015-10-09 18:32 +0000
                Re: pure c on smartphones (and other devices) supercat@casperkitty.com - 2015-10-09 13:02 -0700
              Re: pure c on smartphones (and other devices) glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-06 03:25 +0000
      Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-04 06:27 -0700
        Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-04 06:58 -0700
    Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-04 06:01 -0700
      Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-04 15:33 +0100
        Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-04 07:58 -0700
          Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-04 08:13 -0700
        Re: pure c on smartphones (and other devices) Keith Thompson <kst-u@mib.org> - 2015-10-04 15:42 -0700
          Re: pure c on smartphones (and other devices) David Brown <david.brown@hesbynett.no> - 2015-10-05 09:03 +0200
            Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-05 11:24 +0100
              Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-05 11:27 +0100
            Re: pure c on smartphones (and other devices) Keith Thompson <kst-u@mib.org> - 2015-10-05 09:29 -0700
            Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-06 03:31 -0700
              Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-06 12:29 +0100
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-06 07:18 -0700
                Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-06 18:33 +0100
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-06 11:07 -0700
                Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-07 12:53 +0100
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-07 06:33 -0700
                Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-07 18:21 +0100
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-07 19:10 -0700
  Re: pure c on smartphones (and other devices) Ayan <selfjam@gmail.com> - 2015-10-07 13:41 -0400
    Re: pure c on smartphones (and other devices) fir <profesor.fir@gmail.com> - 2015-10-07 14:01 -0700
      Re: pure c on smartphones (and other devices) Ayan <selfjam@gmail.com> - 2015-10-07 23:09 -0400
        Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 02:26 -0700
        Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-08 11:01 +0100
          Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 03:29 -0700
            Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-08 12:19 +0100
              Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 05:42 -0700
                Re: pure c on smartphones (and other devices) Bartc <bc@freeuk.com> - 2015-10-08 14:41 +0100
                Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 06:55 -0700
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-08 08:53 -0700
                Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 09:21 -0700
                Re: pure c on smartphones (and other devices) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-08 09:46 -0700
                Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 10:07 -0700
                Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-11 23:58 -0700
                Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-09 04:41 -0700
              Re: pure c on smartphones (and other devices) "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-08 05:59 -0700

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