Re: Compiling and linking code from different places in the file system

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c
Subject	Re: Compiling and linking code from different places in the file system
Date	2018-03-09 09:59 +0100
Organization	A noiseless patient Spider
Message-ID	<p7tid4$fmm$1@dont-email.me> (permalink)
References	(12 earlier) <ba477256-00f2-4aaa-bb37-05c93ecc5422@googlegroups.com> <lnmuzjdzla.fsf@kst-u.example.com> <2c91fbad-d3aa-40b7-88a7-124845c1201f@googlegroups.com> <lnefkue814.fsf@kst-u.example.com> <748d0aaa-e82a-4437-b6bd-f70e69c82904@googlegroups.com>

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On 08/03/18 22:36, supercat@casperkitty.com wrote:
> On Thursday, March 8, 2018 at 12:28:50 PM UTC-6, Keith Thompson wrote:
>> supercat@casperkitty.com writes:
>> Are you seriously advocating writing code that assumes long is exactly
>> 32 bits?  Will you at least acknowledge that such code would break on
>> many modern systems?  How is the readability of code that doesn't work
>> relevant?
> 
> I will acknowledge that it has become fashionable for implementations
> where a 32-bit long would have been practical, to define long to be a
> different size.

You are joking, right?  64-bit "long" is 30 years old at least.  And
that is not including specialist systems like Crays, which have had
64-bit long since their first C compiler (and, I believe, 64-bit char,
short and int).

> 
> I would regard readability of code that works correctly *on the platforms
> it is intended to support* is more important than usability on platforms
> that it is not intended to support.

Now, that I agree on.

However, remember that a fair amount of code that is written with for
just one platform ends up migrating to other platforms.  This is often
completely at odds with any predictions the original writers might have
had about the code portability.

So by all means write code that is clear for the intended target - but
make it portable when that is just as clear.  And have compile-time
failures if your assumptions are broken.

That means using int32_t when you want a 32-bit integer but specifically
do not want anything bigger.  The type tells the reader exactly what you
mean - it is /clearer/ and more readable than using "long", as well as
being portable.  What is there to lose?

Long ago, it might well have seemed reasonable to use "long" to mean
"32-bit".  But we are no longer living "long ago".  Certainly this
practice is not remotely justifiable now, even if you are using an old
compiler with no C99 support.

> 
> It doesn't work on 64-bit Linux.  There are many other platforms, including
> nearly all embedded controllers as well as 64-bit Windows, where it works
> just fine.  There's a lot of code on this universe which will never need to
> run natively on a 64-bit Linux system, and where an inability to do so
> would not constitute a defect.

Virtually /all/ 64-bit systems use 64-bit long.  I know of nothing other
than 64-bit Windows where there is a 32-bit long.  And even there, not
every compiler uses 32-bit long - Windows is also the only system I know
of which does not have a well-defined and consistent ABI.

64-bit systems are a minority in the embedded, but they are an
increasing minority.  In the world of network equipment, 64-bit has been
the standard for a decade at least.  For embedded Linux systems, it is
increasingly common - and embedded Linux is becoming increasingly
common.  There are many other 64-bit OS's for the embedded world,
running on PPC, ARM, MIPS, and now RISC-V.  /All/ of them have 64-bit long.

The Windows C world is tiny, especially in the 64-bit realm.  For many
reasons, C is an almost negligible language on that platform - people
use C++, Java, C#, Python, and many other languages.  And equally, in
the world of C programming, Windows is a small target - people write C
for Linux, BSD, *nix, and embedded systems of all sorts.

(RISC-V also has a 128-bit version.  I haven't checked, but I expect it
has 64-bit long and 128-bit long long.)

> 
>>>    4. Cast 32-bit arguments to "long" and then use "%ld".  That would work,
>>>       and is a bit less ugly than the PRI* macros, but it's hardly elegant.
>>
>> I sometimes use "%jd" with a cast to intmax_t, or "%ju" with a cast to
>> uintmax_t, if I'm not sure which predefined type the argument has
>> (though I use "%zu" for size_t).  "%ld" can fail if the argument is
>> wider than long.  In the unlikely case that I have to worry about
>> pre-C99 implementations, I'll use "%ld with a cast to long.
> 
> If none of the values used to compute the argument are larger than 32 bits,
> how could the result be larger than a "long"?
> 
> BTW, freestanding implementations are not required to supply any "printf"-
> style functions, but many programs written for them define their own
> versions that behave analogously to the ones in some version of the
> Standard library.  It would not be uncommon for a program that is being
> compiled on a C11 implementation to include a "sprintf" version which does
> not support all the C99 features.

There is only /one/ situation where that applies - trying to write
modern C on Windows while linking to MS's old C library.  (I believe
newer MSVC comes with C libraries that support C99, but I have no
experience with it myself.)

Other implementations that support C99 in the compiler, support it in
the library.

Embedded toolchains for small systems might optionally have library
versions that are missing features so that the library code is smaller.
 This usually means printf functions without floating point support, but
they may also omit 64-bit integer support.

Thread

Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-01 14:40 +0000
  Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-01 14:55 +0000
    Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-02 21:05 +0000
      Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-03 01:18 +0000
        Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-09 01:03 +0000
      Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-02 22:37 -0800
      Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-09 01:23 +0000
  Re: Compiling and linking code from different places in the file system "James R. Kuyper" <jameskuyper@verizon.net> - 2018-03-01 11:11 -0500
    Re: Compiling and linking code from different places in the file system "James R. Kuyper" <jameskuyper@verizon.net> - 2018-03-01 13:51 -0500
      Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 11:02 -0800
    Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-03 09:48 +0000
      Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 04:06 -0800
        Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 05:24 -0800
          Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 06:43 -0800
    Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-06 13:51 -0800
  Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-01 22:46 +0000
    Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-01 15:27 -0800
    Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-03 12:25 +0000
      Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 04:53 -0800
      Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-03 15:32 +0000
        Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-03 08:02 -0800
        Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-04 07:52 +0000
        Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-04 08:43 +0000
          Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-05 07:58 +0000
            Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-06 21:37 +0000
              Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-07 21:02 +0000
          Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-05 15:29 +0000
            Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-07 04:54 +0000
              Re: Compiling and linking code from different places in the file system Robert Wessel <robertwessel2@yahoo.com> - 2018-03-07 00:33 -0600
                Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-07 09:55 +0000
      Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-04 07:39 +0000
        Re: Compiling and linking code from different places in the file system Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-03-07 05:00 -0800
          Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-07 14:09 +0000
            Re: Compiling and linking code from different places in the file system Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-07 14:26 +0000
              Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-07 16:35 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-07 09:32 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-07 10:11 -0800
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-07 11:12 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-07 12:01 -0800
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-07 15:43 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-07 19:18 -0800
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-08 09:59 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 10:28 -0800
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-08 13:36 -0800
                Re: Compiling and linking code from different places in the file system bartc <bc@freeuk.com> - 2018-03-08 21:47 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-08 15:03 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-09 09:59 +0100
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-09 10:33 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-09 12:27 -0800
                Re: Compiling and linking code from different places in the file system scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 20:48 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-09 13:31 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-10 18:31 +0100
                Re: Compiling and linking code from different places in the file system Robert Wessel <robertwessel2@yahoo.com> - 2018-03-10 13:22 -0600
                Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-10 19:15 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-09 13:28 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-09 14:13 -0800
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-09 14:45 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-10 17:39 +0100
                Re: Compiling and linking code from different places in the file system Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-10 19:00 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 08:26 -0700
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-12 17:06 +0100
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 10:23 -0700
                Re: Compiling and linking code from different places in the file system scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 18:42 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 12:20 -0700
                Re: Compiling and linking code from different places in the file system scott@slp53.sl.home (Scott Lurndal) - 2018-03-12 20:27 +0000
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 14:12 -0700
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-13 11:12 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-12 09:23 -0700
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 10:38 -0700
                Re: Compiling and linking code from different places in the file system David Kleinecke <dkleinecke@gmail.com> - 2018-03-12 11:41 -0700
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 12:10 -0700
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-09 12:09 -0800
                Re: Compiling and linking code from different places in the file system scott@slp53.sl.home (Scott Lurndal) - 2018-03-09 20:46 +0000
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-10 18:35 +0100
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 08:54 -0700
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-13 08:39 +0100
                Re: Compiling and linking code from different places in the file system Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 11:03 -0700
                Re: Compiling and linking code from different places in the file system James Harris <james.harris.1@gmail.com> - 2018-03-11 07:37 +0000
                Re: Compiling and linking code from different places in the file system David Kleinecke <dkleinecke@gmail.com> - 2018-03-11 14:22 -0700
                Re: Compiling and linking code from different places in the file system Spiros Bousbouras <spibou@gmail.com> - 2018-03-11 21:48 +0000
                Re: Compiling and linking code from different places in the file system David Kleinecke <dkleinecke@gmail.com> - 2018-03-11 17:50 -0700
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-11 15:54 -0700
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-12 09:38 -0700
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-08 10:48 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 09:58 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-08 22:03 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 13:55 -0800
                Re: Compiling and linking code from different places in the file system Spiros Bousbouras <spibou@gmail.com> - 2018-03-08 22:38 +0000
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 15:03 -0800
                Re: Compiling and linking code from different places in the file system Spiros Bousbouras <spibou@gmail.com> - 2018-03-08 23:15 +0000
                Re: Compiling and linking code from different places in the file system Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 10:44 -0700
                Re: Compiling and linking code from different places in the file system Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-18 03:47 -0700
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-09 10:10 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-09 10:10 -0800
                Re: Compiling and linking code from different places in the file system jameskuyper@verizon.net - 2018-03-08 14:21 -0800
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 15:10 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-09 10:13 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-09 10:10 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-08 10:28 +0100
                Re: Compiling and linking code from different places in the file system supercat@casperkitty.com - 2018-03-08 10:28 -0800
                Re: Compiling and linking code from different places in the file system David Brown <david.brown@hesbynett.no> - 2018-03-08 22:17 +0100
                Re: Compiling and linking code from different places in the file system Keith Thompson <kst-u@mib.org> - 2018-03-08 13:26 -0800
  Re: Compiling and linking code from different places in the file system "Pascal J. Bourguignon" <pjb@informatimago.com> - 2018-03-14 13:39 +0100

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