[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Noel Chiappa]

    > From: Warner Losh

    > In C I use it all the time to do goto err for common error recovery
    > because C doesn't have anything better.

That's because C doesn't have 'conditions'. (Apparently, from the following
posts, most people here are unfamiliar with them. Too bad, they are a great
idea. OK summary here:

  http://gunkies.org/wiki/Condition_handler

for those who are unfamiliar with the idea.)

I was at one point writing a compiler using a recursive descent parser, and
decided the code would be a lot simpler/cleaner if I had them. (If, for
example, one discovers discovers an un-expected 'end of file', there can be
an extremely large number of procedure invocations in between where that is
discovered, and where it is desirable to handle it. So every possible
intervening procedure would have to have an 'unexpected EOF' return value,
one would have to write code in every possible intervening procedure to
_handle_ an 'unexpected EOF' return value, etc.)'

(Yes, I could have used setjmp/longjmp; those are effectively a limited
version of condition handlers.)

Since C has a stack, it was relatively easy to implement, without any compiler
support: on() became a macro for 'if _on("condition_name")'; _on() was a
partially-assembler procedure which i) stacked the handler (I forget where I
put it; I may have created a special 'condition stack', to avoid too many
changes to the main C stack), and ii) patched the calling procedure's return
point to jump to some code that unstacked the handler, and iii) returned
'false'. If the condition occurred, a return from _on() was simulated,
returning 'true', etc.

So the code had things like:

	on ("unexpected EOF") {
		code to deal with it
		}

With no compiler support, it added a tiny bit of overhead
(stacking/unstacking conditions), but not too bad.

John Wroclawski and someone implemented a very similar thing
entirely in C; IIRC it was built on top of setjmp/longjmp. I don't
recall how it dealt with un-stacking handlers on exit (which mine
did silently).

    Noel

[TUHS] Conditions, AKA exceptions. (Was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Ralph Corderoy]

Hi Noel,

> > In C I use it all the time to do goto err for common error recovery
> > because C doesn't have anything better.
>
> That's because C doesn't have 'conditions'. (Apparently, from the following
> posts, most people here are unfamiliar with them. Too bad, they are a great
> idea. OK summary here:
>
>   http://gunkies.org/wiki/Condition_handler

I wasn't familiar with the term ‘condition handler’.  That page starts

   ‘A condition handler (sometimes exception handler) refers to a
    mechanism in some programming languages which allows the programmer
    to provide code to handle the occurrence of a exception or condition
    (terminology varies, but the substance does not).’

Oh, exceptions.  I know what they are and if you say above that most
people are unfamiliar with them due to their use of goto then that's
probably wrong.

There are good reasons languages like Go chose not to include them.
https://go.dev/doc/faq#exceptions

-- 
Cheers, Ralph.

[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Dan Cross]

On Fri, Mar 10, 2023 at 6:37 AM Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
>
>     > From: Warner Losh
>
>     > In C I use it all the time to do goto err for common error recovery
>     > because C doesn't have anything better.
>
> That's because C doesn't have 'conditions'. (Apparently, from the following
> posts, most people here are unfamiliar with them. Too bad, they are a great
> idea. OK summary here:
>
>   http://gunkies.org/wiki/Condition_handler
>
> for those who are unfamiliar with the idea.)

I don't know if I'd say they're a great idea.

The problem with exceptions (nee conditions, though I most often
associate the term "condition" with Lisp, and in particular Common
Lisp's implementation has a rather different flavor in the ability to
restart execution _at the point where the condition was raised_, even
if the handler is conceptually much higher up in the call stack) is
that they introduce non-linear control flow, which can be very
difficult to reason about. This is especially challenging in code that
may allocate resources and must manually deallocate them (such as C);
without some notion of RAII or finalizers for arbitrary objects. It's
really easy to introduce leaks in code with exceptions, and while
often this is for memory, where you're ok if you're in a garbage
collected language, you're gonna have a bad day when it's for
something like file descriptors (which are much scarcer than memory).
Unless pretty much everything is behind a stack guard, or whatever the
moral equivalent in your language is, you're constrained to handling
the errors at many places in the call stack, in which case, why
bother?

But the point about error handling and the use of `goto` in C in lieu
of something better is well taken, and conditions are _a_ reasonable
mechanism for dealing with the issue. I'd argue that a `Result` monad
and some short-circuiting sugar used in conjunction with RAII is
another that is better. For example in Rust, the result type interacts
with the `?` operator so that, if a call returns a `Result<T, E>`, the
T will be unwrapped if the result is Ok(T), otherwise, the code will
return `Err(E)`. So one can write code that has the brevity of
exceptions without introducing the control-flow weirdness:

    fn make_request(host: &str) -> std::io::Result<()> {
        let req = "hi\r\n".as_bytes();
        std::net::TcpStream::connect(host)?.write(req)?;
        Ok(())
    }

(Note that the TCP stream will be "dropped" after the call to `write`,
and the drop impl on the TcpStream type will close the socket.)

Combined with pattern matching on the error type, this is quite expressive.

> I was at one point writing a compiler using a recursive descent parser, and
> decided the code would be a lot simpler/cleaner if I had them. (If, for
> example, one discovers discovers an un-expected 'end of file', there can be
> an extremely large number of procedure invocations in between where that is
> discovered, and where it is desirable to handle it. So every possible
> intervening procedure would have to have an 'unexpected EOF' return value,
> one would have to write code in every possible intervening procedure to
> _handle_ an 'unexpected EOF' return value, etc.)'
>
> (Yes, I could have used setjmp/longjmp; those are effectively a limited
> version of condition handlers.)
>
> Since C has a stack, it was relatively easy to implement, without any compiler
> support: on() became a macro for 'if _on("condition_name")'; _on() was a
> partially-assembler procedure which i) stacked the handler (I forget where I
> put it; I may have created a special 'condition stack', to avoid too many
> changes to the main C stack), and ii) patched the calling procedure's return
> point to jump to some code that unstacked the handler, and iii) returned
> 'false'. If the condition occurred, a return from _on() was simulated,
> returning 'true', etc.
>
> So the code had things like:
>
>         on ("unexpected EOF") {
>                 code to deal with it
>                 }
>
> With no compiler support, it added a tiny bit of overhead
> (stacking/unstacking conditions), but not too bad.
>
> John Wroclawski and someone implemented a very similar thing
> entirely in C; IIRC it was built on top of setjmp/longjmp. I don't
> recall how it dealt with un-stacking handlers on exit (which mine
> did silently).

The plan9 kernel has something remarkably similar; there is a
pre-process error stack containing the local equivalent of a bunch of
`jmp_buf`'s.  One could write, `if (waserror()) { /* handle cleanup */
}` where, `waserror` would push a jmp_buf onto the stack a la the
`setjmp` equivalent. Code later on could call `error(Ewhatever)` and
that would cache the error somewhere in the proc struct and invoke the
`longjmp` equivalent to jump back to the label at the top of the
stack, where `waserror()` would now return 1. Things would have to
manually `poperror()`, to pop the stack. I'm told that the plan9 C
compilers were callee-save in part to keep these state labels svelte.

This got pulled into the Akaros kernel at one point, and for a while,
we had someone working with us who was pretty prominent in the Linux
community. What was interesting was that he was so used to the `goto
err;` convention from that world that he just could not wrap his head
around how the `waserror()` stuff worked; at one point there was a
sequence like,

    char *foo;

    if (waserror()) {
        free(foo);
        return -1;
    }
    foo = malloc(len);
    something();
    free(foo);
    return 0;

...and the guy just couldn't get how the code inside of the
`waserror()` wasn't trashing the system, since obviously the malloc
was done after `waserror()`, and so the pointer was meaningless at
that point. It took quite a while to explain what was going on.

Btw: I was once told by a reliable authority that the Go developers
considered implementing exceptions, but decided against it because of
the cognitive load it imposes.

        - Dan C.

[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Anthony Martin]

Dan Cross <crossd@gmail.com> once said:
> I'm told that the plan9 C compilers were callee-save in part to keep
> these state labels svelte.

The Plan 9 compilers are caller-save. That means the labels only have
to contain pc and sp. Waserror works well except for one small issue
involving whether or not the compiler decides to store a value to a
non-volatile, non-pointer variable when the value would not be used
after a function call. As in:

	int a;
	a = 1;
	if(waserror()){ /* ... */ }
	a = 2;
	a = foo(a);

The waserror branch may see a == 1 if foo errors.

Ken's compilers are great, though. They don't engage in antisocial
optimizations based on dubious notions of undefined behavior. I'd
prefer my compiler to not elide explicit null checks or loads and
stores from a pointer.

Cheers,
  Anthony

[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Dan Cross]

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On Sun, Mar 12, 2023, 3:39 AM Anthony Martin <ality@pbrane.org> wrote:

> Dan Cross <crossd@gmail.com> once said:
> > I'm told that the plan9 C compilers were callee-save in part to keep
> > these state labels svelte.
>
> The Plan 9 compilers are caller-save. That means the labels only have
> to contain pc and sp.


Indeed. I typo-ed but meant caller-save; it wouldn't be very svelte if it
were the other way around. ;-)


Waserror works well except for one small issue
> involving whether or not the compiler decides to store a value to a
> non-volatile, non-pointer variable when the value would not be used
> after a function call. As in:
>
>         int a;
>         a = 1;
>         if(waserror()){ /* ... */ }
>         a = 2;
>         a = foo(a);
>
> The waserror branch may see a == 1 if foo errors.
>
> Ken's compilers are great, though. They don't engage in antisocial
> optimizations based on dubious notions of undefined behavior. I'd
> prefer my compiler to not elide explicit null checks or loads and
> stores from a pointer.


It is certainly a shame that modern compiler writers have become
essentially hostile to programmers in their pursuit of ever more aggressive
optimizations based on rigid readings of the standard, common sense be
damned.

As for the plan9 C _language_, in the late 80s, it was arguably an
improvement over what ANSI put out. Nowadays, however, I think the inverse
is true. *Shrug*

        - Dan C.

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[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Paul Winalski]

On 3/12/23, Dan Cross <crossd@gmail.com> wrote:
>
> It is certainly a shame that modern compiler writers have become
> essentially hostile to programmers in their pursuit of ever more aggressive
> optimizations based on rigid readings of the standard, common sense be
> damned.

As a compiler developer for many years, IMO the best compilers accept
a wide variety of variations and extensions to the language standard,
but have a strict-standard mode for those who want it.

Dave Cutler's DECwest organization developed and released s C89
compiler for Ultrix that accepted only strict, standard-conforming
syntax and semantics.  No K&R mode, nothing but pure C89.  One
customer called it the Rush Limbaugh of C compilers--extremely
conservative, and you can't reason with it.

-Paul W.

[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[John Cowan]

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On Sun, Mar 12, 2023 at 7:40 AM Dan Cross <crossd@gmail.com> wrote:


> It is certainly a shame that modern compiler writers have become
> essentially hostile to programmers in their pursuit of ever more aggressive
> optimizations based on rigid readings of the standard, common sense be
> damned.
>

Not at all.  It is clear that mainstream C and C++ compilers optimize for
the features most important to mainstream C and C++ programmers, which are:

1) Execution speed.

2) Execution speed.

3) I lied; there is no 3.

If those are not your priorities, use a non-mainstream compiler or a
different programming language.

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[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Alejandro Colomar (man-pages)]

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On Mon, Mar 13, 2023, 04:26 John Cowan <cowan@ccil.org> wrote:

>
>
> On Sun, Mar 12, 2023 at 7:40 AM Dan Cross <crossd@gmail.com> wrote:
>
>
>> It is certainly a shame that modern compiler writers have become
>> essentially hostile to programmers in their pursuit of ever more aggressive
>> optimizations based on rigid readings of the standard, common sense be
>> damned.
>>
>
> Not at all.  It is clear that mainstream C and C++ compilers optimize for
> the features most important to mainstream C and C++ programmers, which are:
>
> 1) Execution speed.
>
> 2) Execution speed.
>
> 3) I lied; there is no 3.
>
> If those are not your priorities, use a non-mainstream compiler or a
> different programming language.
>

Or you can ask GCC to respect your view of the language with things like
-fno-strict-aliasing, -fwrapv, and -fno-trapv.

>

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[TUHS] Re: I can't drive 55: "GOTO considered harmful" 55th anniversary

[Dan Cross]

On Mon, Mar 13, 2023 at 6:41 AM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
> Or you can ask GCC to respect your view of the language with things like -fno-strict-aliasing, -fwrapv, and -fno-trapv.

The problem that is that you are then no longer programming in "C",
but rather some dialect of "C" that happens to share the same syntax,
but with different semantics. That may be fine, or it may not, but it
can lead to all sorts of footgun traps if one is not careful.

        - Dan C.

[TUHS] [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Alejandro Colomar]

Hi Dan,

On 3/13/23 13:19, Dan Cross wrote:
> On Mon, Mar 13, 2023 at 6:41 AM Alejandro Colomar (man-pages)
> <alx.manpages@gmail.com> wrote:
>> Or you can ask GCC to respect your view of the language with things like -fno-strict-aliasing, -fwrapv, and -fno-trapv.
> 
> The problem that is that you are then no longer programming in "C",
> but rather some dialect of "C" that happens to share the same syntax,
> but with different semantics. That may be fine, or it may not, but it
> can lead to all sorts of footgun traps if one is not careful.

Well, it depends on what you call "C".  There are many dialects,
and I'm not sure there's any which I'd call "C".

The 3 main dialects are "ISO C", "GNU C", and "K&R C".  And then
there are subdialects of them.  We could say "C" is "ISO C", since,
well, it's _the_ standard.  But then, ISO C shares the aliasing
issues that GNU C has, so by avoiding the GNU C compiler you're
not avoiding the issues we're talking about; moving to a compiler
that only talks ISO C is going to keep the issues.  You'll need
a compiler that talks K&R C, or some other dialect that doesn't
have aliasing issues.

At that point, since you already need a subdialect of C, GCC is
one such compiler, since it provides a comprehensive set of flags
to tune your dialect.

Or you could move to a compiler that talks its own dialect
(probably some subdialect of K&R C, as I expect Plan9 C is, but
I never tried it).  But that's not much different from asking
such dialect to GCC.

Cheers,

Alex

> 
>         - Dan C.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 8:43 AM Alejandro Colomar
<alx.manpages@gmail.com> wrote:
> On 3/13/23 13:19, Dan Cross wrote:
> > On Mon, Mar 13, 2023 at 6:41 AM Alejandro Colomar (man-pages)
> > <alx.manpages@gmail.com> wrote:
> >> Or you can ask GCC to respect your view of the language with things like -fno-strict-aliasing, -fwrapv, and -fno-trapv.
> >
> > The problem that is that you are then no longer programming in "C",
> > but rather some dialect of "C" that happens to share the same syntax,
> > but with different semantics. That may be fine, or it may not, but it
> > can lead to all sorts of footgun traps if one is not careful.
>
> Well, it depends on what you call "C".  There are many dialects,
> and I'm not sure there's any which I'd call "C".

That's precisely the problem. :-)

        - Dan C.


> The 3 main dialects are "ISO C", "GNU C", and "K&R C".  And then
> there are subdialects of them.  We could say "C" is "ISO C", since,
> well, it's _the_ standard.  But then, ISO C shares the aliasing
> issues that GNU C has, so by avoiding the GNU C compiler you're
> not avoiding the issues we're talking about; moving to a compiler
> that only talks ISO C is going to keep the issues.  You'll need
> a compiler that talks K&R C, or some other dialect that doesn't
> have aliasing issues.
>
> At that point, since you already need a subdialect of C, GCC is
> one such compiler, since it provides a comprehensive set of flags
> to tune your dialect.
>
> Or you could move to a compiler that talks its own dialect
> (probably some subdialect of K&R C, as I expect Plan9 C is, but
> I never tried it).  But that's not much different from asking
> such dialect to GCC.
>
> Cheers,
>
> Alex
>
> >
> >         - Dan C.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Paul Winalski]

On 3/13/23, Alejandro Colomar <alx.manpages@gmail.com> wrote:
>
> Well, it depends on what you call "C".  There are many dialects,
> and I'm not sure there's any which I'd call "C".
>
> The 3 main dialects are "ISO C", "GNU C", and "K&R C".  And then
> there are subdialects of them.  We could say "C" is "ISO C", since,
> well, it's _the_ standard.

Note that the goal of a programming language standards committee is
very different from the goal of those who use the language.  The
committee's goal is to standardize existing practice of the language
in a way that is implementable on the widest range of hardware and OS
platforms, and to provide a controlled way to add language extensions.

The goal of users is to get their job done.

The advantage of programming in strict ISO C is that the resulting
code will run just about anywhere.  If you don't care about that (and
I'd wager most programmers don't) then ignore the standard.

> But then, ISO C shares the aliasing
> issues that GNU C has, so by avoiding the GNU C compiler you're
> not avoiding the issues we're talking about; moving to a compiler
> that only talks ISO C is going to keep the issues.  You'll need
> a compiler that talks K&R C, or some other dialect that doesn't
> have aliasing issues.

As someone pointed out, the three things that most programmers value
are execution speed, execution speed, and execution speed.  Aliasing
issues greatly hamper what a modern optimizing compiler can do and
still generate semantically correct code.

> At that point, since you already need a subdialect of C, GCC is
> one such compiler, since it provides a comprehensive set of flags
> to tune your dialect.

All the best commercial optimizing compilers do that these days.  It's
a way of having your semantic cake and being able to eat it (fast
execution speed), too.

-Paul W.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Clem Cole]

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On Mon, Mar 13, 2023 at 12:00 PM Paul Winalski <paul.winalski@gmail.com>
wrote:

> ... The committee's goal is to standardize existing practice of the
> language
> in a way that is implementable on the widest range of hardware and OS
> platforms, *and to provide a controlled way to add language extensions.*

Ah, the problem, of course, is right there.

Too many people try to "fix" programming languages, particularly academics
and folks working on a new PhD. Other folks (Gnu is the best example IMO)
want to change things so the compiler writers (and it seems like the Linux
kernel developers) can do something "better" or "more easily."  As someone
(I think Dan Cross) said, when that happens, it's no longer C. Without
Dennis here to say "whoa," - the committee is a tad open loop.   Today's
language is hardly the language I learned before the "White Book" existed
in the early/mid 1970s.  It's actually quite sad.   I'm not so sure we are
"better" off.

Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
requiring and fall back at least to K&R2 -- keep it simple. The truth is
that we still use the language today is that K&R2 C was then (and still is)
good enough and got (gets) the job done extremely well.    Overall, I'm not
sure all the new "features" have added all that much.
ᐧ

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[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Larry McVoy]

> Dennis without here to say "whoa," - the committee is a tad open loop.   

Having someone who can say "no" is critical to any software project.  What
doesn't go in is easily way more important than what does go in.  You can
surround a really great idea with enough crap that all you really get is
crap.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Steve Nickolas]

On Mon, 13 Mar 2023, Clem Cole wrote:

> Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
> requiring and fall back at least to K&R2 -- keep it simple. The truth is
> that we still use the language today is that K&R2 C was then (and still is)
> good enough and got (gets) the job done extremely well.    Overall, I'm not
> sure all the new "features" have added all that much.

C99 did introduce one thing I use: <stdint.h>

Beyond that, I still code strict C89.  I simply treat the language itself 
as ossified.  I also still make assumptions about the compiler that might 
not still be true, so for example

  unsigned short a;
  unsigned char b;

  b=0xFF;
  a=b<<8;

I expect to return 0 even though the logical answer is 0xFF00, and I 
_always_ code it like this:

  b=0xFF;
  a=b;
  a<<=8;

or alternatively

  b=0xFF;
  a=((unsigned short) b)<<8;

and there's other defensive stuff I do.  I honestly don't see the point in 
the other changes to the language and feel they take C away from what it 
has always been.

-uso.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 3:16 PM Steve Nickolas <usotsuki@buric.co> wrote:
> On Mon, 13 Mar 2023, Clem Cole wrote:
> > Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
> > requiring and fall back at least to K&R2 -- keep it simple. The truth is
> > that we still use the language today is that K&R2 C was then (and still is)
> > good enough and got (gets) the job done extremely well.    Overall, I'm not
> > sure all the new "features" have added all that much.
>
> C99 did introduce one thing I use: <stdint.h>
>
> Beyond that, I still code strict C89.  I simply treat the language itself
> as ossified.  I also still make assumptions about the compiler that might
> not still be true, so for example
>
>   unsigned short a;
>   unsigned char b;
>
>   b=0xFF;
>   a=b<<8;
>
> I expect to return 0 even though the logical answer is 0xFF00,

I don't know why one would expect that. `b` will be promoted to
(signed!!) `int` before the shift, and then the result of that
assigned to `a`, wrapping as needed to fit into the `unsigned short`;
on most reasonable systems the UB gods won't be angered.

OTOH, `uint16_t mul(uint16_t a, uint16_t b) { return a * b; }` is a UB
minefield on most systems.

> and I
> _always_ code it like this:
>
>   b=0xFF;
>   a=b;
>   a<<=8;

Curiously, this will be subject to the same type promotion rules as
the original.

> or alternatively
>
>   b=0xFF;
>   a=((unsigned short) b)<<8;

As will this. In fact, the cast here is completely superfluous; the
shift will still be done using after promotion to signed int.

> and there's other defensive stuff I do.  I honestly don't see the point in
> the other changes to the language and feel they take C away from what it
> has always been.

I think an issue is that there is what people _think_ C does, and what
C _actually_ does, and the two are often discordant; this is why I
think you see people tweaking compiler options to create a dialect
that's reasonable to program in: given a large-enough code base, you
inevitably end up with a very peculiar dialect, which compounds the
problem. For example, I'm quite sure that the C dialect that Linux
uses is not the same as the C that Windows uses, and so on. The
compiler writers now seem very much of the mind where you point this
out and they look at you and say, "tough."

        - Dan C.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Alejandro Colomar (man-pages)]

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On Mon, Mar 13, 2023, 21:27 Dan Cross <crossd@gmail.com> wrote:

> On Mon, Mar 13, 2023 at 3:16 PM Steve Nickolas <usotsuki@buric.co> wrote:
> > On Mon, 13 Mar 2023, Clem Cole wrote:
> > > Frankly, I'd probably rather see ISO drop a bunch of the stuff they
> are now
> > > requiring and fall back at least to K&R2 -- keep it simple. The truth
> is
> > > that we still use the language today is that K&R2 C was then (and
> still is)
> > > good enough and got (gets) the job done extremely well.    Overall,
> I'm not
> > > sure all the new "features" have added all that much.
> >
> > C99 did introduce one thing I use: <stdint.h>
> >
> > Beyond that, I still code strict C89.  I simply treat the language itself
> > as ossified.  I also still make assumptions about the compiler that might
> > not still be true, so for example
> >
> >   unsigned short a;
> >   unsigned char b;
> >
> >   b=0xFF;
> >   a=b<<8;
> >
> > I expect to return 0 even though the logical answer is 0xFF00,
>
> I don't know why one would expect that. `b` will be promoted to
> (signed!!) `int` before the shift, and then the result of that
> assigned to `a`, wrapping as needed to fit into the `unsigned short`;
> on most reasonable systems the UB gods won't be angered.
>

C23 will be adding new types that don't have this issue (default promotion
to in).  If a variable has 3 bits, it will have 3 bits (until you mix it
with a wider variable).

Another whole class of Undefined Behavior (in ISO C) or
implementation-defined behavior (K&R C) is 2's complement arithmetic which
has never been portable, until C23.  So it's not all bad.


> OTOH, `uint16_t mul(uint16_t a, uint16_t b) { return a * b; }` is a UB
> minefield on most systems.
>
> > and I
> > _always_ code it like this:
> >
> >   b=0xFF;
> >   a=b;
> >   a<<=8;
>
> Curiously, this will be subject to the same type promotion rules as
> the original.
>
> > or alternatively
> >
> >   b=0xFF;
> >   a=((unsigned short) b)<<8;
>
> As will this. In fact, the cast here is completely superfluous; the
> shift will still be done using after promotion to signed int.
>
> > and there's other defensive stuff I do.  I honestly don't see the point
> in
> > the other changes to the language and feel they take C away from what it
> > has always been.
>
> I think an issue is that there is what people _think_ C does, and what
> C _actually_ does, and the two are often discordant;


Indeed.  That's my feeling too.  When discussing about features that
programmers don't understand why they were added, it's rather often the
case that the feature has been there for longer than they thought (if not
since forever).

this is why I
> think you see people tweaking compiler options to create a dialect
> that's reasonable to program in: given a large-enough code base, you
> inevitably end up with a very peculiar dialect, which compounds the
> problem. For example, I'm quite sure that the C dialect that Linux
> uses is not the same as the C that Windows uses, and so on. The
> compiler writers now seem very much of the mind where you point this
> out and they look at you and say, "tough."
>

Even "safe" Rust is having its share of Undefined Behavior.  Let's see how
they deal with it.
<https://github.com/rust-lang/rust/issues/107975>


>         - Dan C.
>

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[TUHS] Re: [TUHS]: C dialects

[Luther Johnson]

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I agree with everything you just said here.

One of the motivations behind new dialects and languages, which I think 
is very harmful, is the idea that we can and should, engineer the 
necessity to know and understand what we are doing when we program in a 
given language. I'm not talking about semantic leverage, higher level 
languages with more abstract functions on more abstract data, there are 
real benefits there, we will all probably agree to that.

I'm talking more about where the intent is to invest languages with more 
"safety", "good practices", to bake certain preferences into language 
features, so that writers no longer recognize these as engineering 
choices, and the language as a means of expression of any choice we 
might make, but that the language has built-in "the right way" to do 
things, and if the program compiles and runs at all, then it must be 
safe and working in certain respects.

No matter what language, craft and knowledge are not optional. The 
language that we choose for a problem domain wants to give us freedom to 
express our choices, while taking care of the things that wold otherwise 
weigh us down. Some people would say that's exactly what the new 
dialects bring us, but I see too much artificial orthodoxy invented last 
week, and too many declarations of the "one true way", in many of the 
most recent languages, for my taste.

On 03/13/2023 12:00 PM, Clem Cole wrote:
>
>
> On Mon, Mar 13, 2023 at 12:00 PM Paul Winalski 
> <paul.winalski@gmail.com <mailto:paul.winalski@gmail.com>> wrote:
>
>     ... Thecommittee's goal is to standardize existing practice of the
>     language
>     in a way that is implementable on the widest range of hardware and OS
>     platforms, _/and to provide a controlled way to add language
>     extensions./_
>
> Ah, the problem, of course, is right there.
>
> Too many people try to "fix" programming languages, particularly 
> academics and folks working on a new PhD. Other folks (Gnu is the best 
> example IMO) want to change things so the compiler writers (and it 
> seems like the Linux kernel developers) can do something "better" or 
> "more easily." As someone (I think Dan Cross) said, when that happens, 
> it's no longer C. Without Dennis here to say "whoa," - the 
> committee is a tad open loop.   Today's language is hardly the 
> language I learned before the "White Book" existed in the early/mid 
> 1970s.  It's actually quite sad.   I'm not so sure we are "better" off.
>
> Frankly, I'd probably rather see ISO drop a bunch of the stuff they 
> are now requiring and fall back at least to K&R2 -- keep it simple. 
> The truth is that we still use the language today is that K&R2 C was 
> then (and still is) good enough and got (gets) the job done extremely 
> well. Overall, I'm not sure all the new "features" have added all that 
> much.
> ᐧ


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[TUHS] Re: [TUHS]: C dialects

[Luther Johnson]

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I meant to say engineer "out" the necessity ...doh ! I shot myself in 
the foot there ...

On 03/13/2023 12:24 PM, Luther Johnson wrote:
>
> I agree with everything you just said here.
>
> One of the motivations behind new dialects and languages, which I 
> think is very harmful, is the idea that we can and should, engineer 
> the necessity to know and understand what we are doing when we program 
> in a given language. I'm not talking about semantic leverage, higher 
> level languages with more abstract functions on more abstract data, 
> there are real benefits there, we will all probably agree to that.
>
> I'm talking more about where the intent is to invest languages with 
> more "safety", "good practices", to bake certain preferences into 
> language features, so that writers no longer recognize these as 
> engineering choices, and the language as a means of expression of any 
> choice we might make, but that the language has built-in "the right 
> way" to do things, and if the program compiles and runs at all, then 
> it must be safe and working in certain respects.
>
> No matter what language, craft and knowledge are not optional. The 
> language that we choose for a problem domain wants to give us freedom 
> to express our choices, while taking care of the things that wold 
> otherwise weigh us down. Some people would say that's exactly what the 
> new dialects bring us, but I see too much artificial orthodoxy 
> invented last week, and too many declarations of the "one true way", 
> in many of the most recent languages, for my taste.
>
> On 03/13/2023 12:00 PM, Clem Cole wrote:
>>
>>
>> On Mon, Mar 13, 2023 at 12:00 PM Paul Winalski 
>> <paul.winalski@gmail.com <mailto:paul.winalski@gmail.com>> wrote:
>>
>>     ... Thecommittee's goal is to standardize existing practice of
>>     the language
>>     in a way that is implementable on the widest range of hardware and OS
>>     platforms, _/and to provide a controlled way to add language
>>     extensions./_
>>
>> Ah, the problem, of course, is right there.
>>
>> Too many people try to "fix" programming languages, particularly 
>> academics and folks working on a new PhD. Other folks (Gnu is the 
>> best example IMO) want to change things so the compiler writers (and 
>> it seems like the Linux kernel developers) can do something "better" 
>> or "more easily." As someone (I think Dan Cross) said, when that 
>> happens, it's no longer C. Without Dennis here to say "whoa," - the 
>> committee is a tad open loop.   Today's language is hardly the 
>> language I learned before the "White Book" existed in the early/mid 
>> 1970s.  It's actually quite sad.   I'm not so sure we are "better" off.
>>
>> Frankly, I'd probably rather see ISO drop a bunch of the stuff they 
>> are now requiring and fall back at least to K&R2 -- keep it simple. 
>> The truth is that we still use the language today is that K&R2 C was 
>> then (and still is) good enough and got (gets) the job done extremely 
>> well.    Overall, I'm not sure all the new "features" have added all 
>> that much.
>> ᐧ
>


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[TUHS] Re: [TUHS]: C dialects

[John Cowan]

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On Mon, Mar 13, 2023 at 3:24 PM Luther Johnson <luther@makerlisp.com> wrote:

> I'm talking more about where the intent is to invest languages with more
> "safety", "good practices", to bake certain preferences into language
> features, so that writers no longer recognize these as engineering choices,
> and the language as a means of expression of any choice we might make, but
> that the language has built-in "the right way" to do things, and if the
> program compiles and runs at all, then it must be safe and working in
> certain respects.
>

ORLY?  Do you reject C, then, because it does not support self-modifying
code or the ability to jump into the middle of a procedure without going
through the prologue?  These are baked-in preferences, and if a C program
compiles at all, you can be sure that it does neither of these things, even
if it would benefit your program greatly if they were available.

Some people would say that's exactly what the new dialects bring us, but I
> see too much artificial orthodoxy invented last week, and too many
> declarations of the "one true way", in many of the most recent languages,
> for my taste.
>

Since you agree that it is a matter of taste, there can of course be no
disputing it.

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[TUHS] Re: [TUHS]: C dialects

[Joseph Holsten]

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Is TUHS still the right place for this discussion?

On Tue, Mar 14, 2023, at 12:48, John Cowan wrote:
> 
> 
> On Mon, Mar 13, 2023 at 3:24 PM Luther Johnson <luther@makerlisp.com> wrote:
>> I'm talking more about where the intent is to invest languages with more "safety", "good practices", to bake certain preferences into language features, so that writers no longer recognize these as engineering choices, and the language as a means of expression of any choice we might make, but that the language has built-in "the right way" to do things, and if the program compiles and runs at all, then it must be safe and working in certain respects.
>> 
> 
> ORLY?  Do you reject C, then, because it does not support self-modifying code or the ability to jump into the middle of a procedure without going through the prologue?  These are baked-in preferences, and if a C program compiles at all, you can be sure that it does neither of these things, even if it would benefit your program greatly if they were available.
> 
>> Some people would say that's exactly what the new dialects bring us, but I see too much artificial orthodoxy invented last week, and too many declarations of the "one true way", in many of the most recent languages, for my taste.
> 
> Since you agree that it is a matter of taste, there can of course be no disputing it.

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[TUHS] Re: [TUHS]: C dialects

[Luther Johnson]

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I take your points. C gives a lot of freedom, but all things are not 
possible. I think what comes to mind for me is when I see the idea of 
trying to limit solutions to use only certain certain "design patterns", 
I usually would go in the direction of more freedom and less rules.

On 03/14/2023 12:48 PM, John Cowan wrote:
>
>
> On Mon, Mar 13, 2023 at 3:24 PM Luther Johnson <luther@makerlisp.com 
> <mailto:luther@makerlisp.com>> wrote:
>
>     I'm talking more about where the intent is to invest languages
>     with more "safety", "good practices", to bake certain preferences
>     into language features, so that writers no longer recognize these
>     as engineering choices, and the language as a means of expression
>     of any choice we might make, but that the language has built-in
>     "the right way" to do things, and if the program compiles and runs
>     at all, then it must be safe and working in certain respects.
>
>
> ORLY?  Do you reject C, then, because it does not support 
> self-modifying code or the ability to jump into the middle of a 
> procedure without going through the prologue?  These are baked-in 
> preferences, and if a C program compiles at all, you can be sure that 
> it does neither of these things, even if it would benefit your program 
> greatly if they were available.
>
>     Some people would say that's exactly what the new dialects bring
>     us, but I see too much artificial orthodoxy invented last week,
>     and too many declarations of the "one true way", in many of the
>     most recent languages, for my taste.
>
>
> Since you agree that it is a matter of taste, there can of course be 
> no disputing it.


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[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Paul Winalski]

On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
>
> Too many people try to "fix" programming languages, particularly academics
> and folks working on a new PhD. Other folks (Gnu is the best example IMO)
> want to change things so the compiler writers (and it seems like the Linux
> kernel developers) can do something "better" or "more easily."  As someone
> (I think Dan Cross) said, when that happens, it's no longer C. Without
> Dennis here to say "whoa," - the committee is a tad open loop.   Today's
> language is hardly the language I learned before the "White Book" existed
> in the early/mid 1970s.  It's actually quite sad.   I'm not so sure we are
> "better" off.

I'd rather see programming language standards committees restrict
their activity to regularizing existing practice.  Let vendors and
others innovate by adding non-standard extensions.  Then take those
that are really useful and adopt them as part of the standard.  But
the committee itself should not be doing design.  We all know what
they say about "design by committee", and it's all too true.

Programming language standards committees also tend to suffer from
what I call the "dog and fire hydrant" problem.  The committee members
are like a pack of dogs, with the standard being the fire hydrant.
Each dog doesn't consider the fire hydrant "theirs" until they've
pissed on it.  Programming languages get treated the same way by
standards committee members.

-Paul W.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Bakul Shah]

In hindsight Algol68 may have been the last committee designed
language that was good. It got a lot of flack back then but its
imperfections seem tiny in comparison to most of the languages
designed since then.

> On Mar 13, 2023, at 1:48 PM, Paul Winalski <paul.winalski@gmail.com> wrote:
> 
> I'd rather see programming language standards committees restrict
> their activity to regularizing existing practice.  Let vendors and
> others innovate by adding non-standard extensions.  Then take those
> that are really useful and adopt them as part of the standard.  But
> the committee itself should not be doing design.  We all know what
> they say about "design by committee", and it's all too true.
> 
> Programming language standards committees also tend to suffer from
> what I call the "dog and fire hydrant" problem.  The committee members
> are like a pack of dogs, with the standard being the fire hydrant.
> Each dog doesn't consider the fire hydrant "theirs" until they've
> pissed on it.  Programming languages get treated the same way by
> standards committee members.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Larry McVoy]

On Mon, Mar 13, 2023 at 04:48:04PM -0400, Paul Winalski wrote:
> On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
> >
> > Too many people try to "fix" programming languages, particularly academics
> > and folks working on a new PhD. Other folks (Gnu is the best example IMO)
> > want to change things so the compiler writers (and it seems like the Linux
> > kernel developers) can do something "better" or "more easily."  As someone
> > (I think Dan Cross) said, when that happens, it's no longer C. Without
> > Dennis here to say "whoa," - the committee is a tad open loop.   Today's
> > language is hardly the language I learned before the "White Book" existed
> > in the early/mid 1970s.  It's actually quite sad.   I'm not so sure we are
> > "better" off.
> 
> I'd rather see programming language standards committees restrict
> their activity to regularizing existing practice.  Let vendors and
> others innovate by adding non-standard extensions.  Then take those
> that are really useful and adopt them as part of the standard.  But
> the committee itself should not be doing design.  We all know what
> they say about "design by committee", and it's all too true.

I wish I had a magic wand and could upvote this more.  You are exactly
right, that is exactly what standards should do, maybe with a little
leeway to resolve conflicts between 2 good ideas, but no more than
that.

But ego gets involved and things go pear shaped.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Paul Winalski]

On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
>
> Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
> requiring and fall back at least to K&R2 -- keep it simple.

I agree.  Every language has toxic features--things that seemed like
good ideas at the time but turn out to have been mistakes when they're
better understood.  Every good programming shop has its rules
concerning certain language features or practices that are not allowed
in the code, usually for safety or maintainability reasons.

Dropping toxic features from a language does happen at standards
committees, but it's rare.  The best case I know of where this
happened was when the international standard for PL/I came out.  They
started with IBM PL/I but then dropped a bunch of features that were
either obsolete (e.g., sterling pictures) or downright dangerous
(e.g., the DEFAULT statement).

On the other side of the spectrum you have the BASIC standards
committee.  BASIC has always had to live down a reputation that it's a
"toy language" not suitable for "serious programming".  The standards
committee seems to have suffered from an inferiority complex, and it
seemed from my perspective that as fast as the PL/I committee chucked
out toxic language, the BASIC committee adopted them.  The result is a
bloated, grotesque monstrosity that little resembles the simple, clean
Dartmouth BASIC 6 that was the first programming language I learned
(from the DTSS TEACH command).

-Paul W.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Bakul Shah]

On Mar 13, 2023, at 2:00 PM, Paul Winalski <paul.winalski@gmail.com> wrote:
> 
> On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
>> 
>> Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
>> requiring and fall back at least to K&R2 -- keep it simple.
> 
> I agree.  Every language has toxic features--things that seemed like
> good ideas at the time but turn out to have been mistakes when they're
> better understood.  Every good programming shop has its rules
> concerning certain language features or practices that are not allowed
> in the code, usually for safety or maintainability reasons.

You can't drop features from a widely deployed language; but while
we are dreaming, what I'd like to see is a total *ban* on any and
all optimizations. What you get is what you see!

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 5:08 PM Bakul Shah <bakul@iitbombay.org> wrote:
> On Mar 13, 2023, at 2:00 PM, Paul Winalski <paul.winalski@gmail.com> wrote:
> >
> > On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
> >>
> >> Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
> >> requiring and fall back at least to K&R2 -- keep it simple.
> >
> > I agree.  Every language has toxic features--things that seemed like
> > good ideas at the time but turn out to have been mistakes when they're
> > better understood.  Every good programming shop has its rules
> > concerning certain language features or practices that are not allowed
> > in the code, usually for safety or maintainability reasons.
>
> You can't drop features from a widely deployed language; but while
> we are dreaming, what I'd like to see is a total *ban* on any and
> all optimizations. What you get is what you see!

Hey, they dropped `gets` from the standard library! Never say never.

        - Dan C.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dave Horsfall]

On Mon, 13 Mar 2023, Dan Cross wrote:

> Hey, they dropped `gets` from the standard library! Never say never.

When did that finally happen?  Last I looked, gets() was still part of 
POSIX, and hence couldn't be dropped...

Trivia: I think it was OpenBSD that nobbled gets() to print a warning 
whenever it was invoked :-)

-- Dave

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dave Horsfall]

On Tue, 14 Mar 2023, Dave Horsfall followed himself up:

> Trivia: I think it was OpenBSD that nobbled gets() to print a warning 
> whenever it was invoked :-)

FreeBSD 10.4 (old, I know):

    c.c:1:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int] main()
    ^~~~
    c.c:2:3: warning: implicit declaration of function 'gets' is invalid in C99
	  [-Wimplicit-function-declaration]
    { gets(); }
      ^
    2 warnings generated.
    /tmp/c-36bc21.o: In function `main':
    c.c:(.text+0x4): warning: warning: this program uses gets(), which is unsafe.
    aneurin% ./c
    warning: this program uses gets(), which is unsafe.
    <CR>
    aneurin% 

On the MacBook (10.13.6 High Sierra):

    c.c:1:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
main()
    ^
    c.c:2:3: warning: implicit declaration of function 'gets' is invalid in C99
	  [-Wimplicit-function-declaration]
    { gets(); }
      ^
    2 warnings generated.
    mackie:tmp dave$ ./c
    warning: this program uses gets(), which is unsafe.
    <CR>

    And it core-dumped,,,


(I don't have access to my Penguin/OS lapdog right now.)

I think that it's trying to tel me something :-)

-- Dave

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 6:47 PM Dave Horsfall <dave@horsfall.org> wrote:
>
> On Tue, 14 Mar 2023, Dave Horsfall followed himself up:
>
> > Trivia: I think it was OpenBSD that nobbled gets() to print a warning
> > whenever it was invoked :-)
>
> FreeBSD 10.4 (old, I know):
>
>     c.c:1:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int] main()
>     ^~~~
>     c.c:2:3: warning: implicit declaration of function 'gets' is invalid in C99
>           [-Wimplicit-function-declaration]
>     { gets(); }
>       ^
>     2 warnings generated.
>     /tmp/c-36bc21.o: In function `main':
>     c.c:(.text+0x4): warning: warning: this program uses gets(), which is unsafe.
>     aneurin% ./c
>     warning: this program uses gets(), which is unsafe.
>     <CR>
>     aneurin%
>
> On the MacBook (10.13.6 High Sierra):
>
>     c.c:1:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
> main()
>     ^
>     c.c:2:3: warning: implicit declaration of function 'gets' is invalid in C99
>           [-Wimplicit-function-declaration]
>     { gets(); }
>       ^
>     2 warnings generated.
>     mackie:tmp dave$ ./c
>     warning: this program uses gets(), which is unsafe.
>     <CR>
>
>     And it core-dumped,,,

I should hope so! It takes a pointer to a buffer as an argument, and
it appears you elided that. :-D

> (I don't have access to my Penguin/OS lapdog right now.)
>
> I think that it's trying to tel me something :-)

gets: unsafe at any C.

        - Dan C.

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Dan Cross]

On Mon, Mar 13, 2023 at 6:15 PM Dave Horsfall <dave@horsfall.org> wrote:
> On Mon, 13 Mar 2023, Dan Cross wrote:
> > Hey, they dropped `gets` from the standard library! Never say never.
>
> When did that finally happen?  Last I looked, gets() was still part of
> POSIX, and hence couldn't be dropped...

It was (finally!!) dropped from ISO C in C11.

It's a shame POSIX is keeping it around, but it appears you're right:
https://pubs.opengroup.org/onlinepubs/9699919799/

In fairness, this does say it may be removed from a later standard.

        - Dan C.

> Trivia: I think it was OpenBSD that nobbled gets() to print a warning
> whenever it was invoked :-)
>
> -- Dave

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Chet Ramey]

On 3/13/23 8:21 PM, Dan Cross wrote:

> It's a shame POSIX is keeping it around, but it appears you're right:
> https://pubs.opengroup.org/onlinepubs/9699919799/
> 
> In fairness, this does say it may be removed from a later standard.

It's been removed in the upcoming issue 8.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Bakul Shah]

On Mar 13, 2023, at 2:14 PM, Dan Cross <crossd@gmail.com> wrote:
> 
> On Mon, Mar 13, 2023 at 5:08 PM Bakul Shah <bakul@iitbombay.org> wrote:
>> On Mar 13, 2023, at 2:00 PM, Paul Winalski <paul.winalski@gmail.com> wrote:
>>> 
>>> On 3/13/23, Clem Cole <clemc@ccc.com> wrote:
>>>> 
>>>> Frankly, I'd probably rather see ISO drop a bunch of the stuff they are now
>>>> requiring and fall back at least to K&R2 -- keep it simple.
>>> 
>>> I agree.  Every language has toxic features--things that seemed like
>>> good ideas at the time but turn out to have been mistakes when they're
>>> better understood.  Every good programming shop has its rules
>>> concerning certain language features or practices that are not allowed
>>> in the code, usually for safety or maintainability reasons.
>> 
>> You can't drop features from a widely deployed language; but while
>> we are dreaming, what I'd like to see is a total *ban* on any and
>> all optimizations. What you get is what you see!
> 
> Hey, they dropped `gets` from the standard library! Never say never.

It is easy to see that incorrect use of gets can lead to buffer
overflow problems so they "fixed" the easier downstream issue but
not the root cause! And that is the problem. Easy things are fixed
but nobody dares fix more fundamental problems.

And that was my point. All that standardization committees can do
is tweak a few things here and there. 

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Paul Winalski]

On 3/13/23, Bakul Shah <bakul@iitbombay.org> wrote:
>
> You can't drop features from a widely deployed language;

It has been done, with advanced warning of the deprecation, and over
several iterations of the standard so that there's advanced warning.
But it's rare and not advisable.

But you can create new subsets of the full standard.

> but while
> we are dreaming, what I'd like to see is a total *ban* on any and
> all optimizations. What you get is what you see!
>
Be careful what you wish for.  That just won't fly on modern computer
architectures, with their many execution units and complicated memory
hierarchies.  Not if you want anything resembling reasonable
performance that is also maintainable.

-Paul W.

[TUHS] C dialects

[Ralph Corderoy]

Hi Bakul,

> ...what I'd like to see is a total *ban* on any and all optimizations.
> What you get is what you see!

I think you'd see less clear source code as, once again, programmers
chased efficiency by contorting the source to squeeze the best out of a
dumb compiler.

I think Ted said it well.
Let the compiler squeeze all it can out of the letter of the standard.
Let the programmer have the compiler abide by the spirit of the language.

-- 
Cheers, Ralph.

[TUHS] Re: C dialects

[John Cowan]

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On Tue, Mar 14, 2023 at 6:05 AM Ralph Corderoy <ralph@inputplus.co.uk>
wrote:


> Let the compiler squeeze all it can out of the letter of the standard.
> Let the programmer have the compiler abide by the spirit of the language.
>

Right.  And what is the spirit of C?  I contend that it is this:
"Conformant code flies faster than the lightning, and non-conformant code
makes demons fly out of your nose, because if you have code that exhibits
any of the 193 (or whatever) C99 undefined behaviors plus however many
later standards have added, IT'S YOUR FAULT."

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[TUHS] Re: C dialects

[Thomas Paulsen]

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[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[John Cowan]

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On Mon, Mar 13, 2023 at 5:00 PM Paul Winalski <paul.winalski@gmail.com>
wrote:

Dropping toxic features from a language does happen at standards
> committees, but it's rare.  The best case I know of where this
> happened was when the international standard for PL/I came out.  They
> started with IBM PL/I but then dropped a bunch of features that were
> either obsolete (e.g., sterling pictures) or downright dangerous
> (e.g., the DEFAULT statement).
>

That actually happened twice.  The 1976 standard removed features from IBM
PL/I; the 1981 Subset G standard removed even more features.  (A few were
added back in the 1987 revision of Subset G.)

> On the other side of the spectrum you have the BASIC standards
> committee.  BASIC has always had to live down a reputation that it's a
> "toy language" not suitable for "serious programming".  The standards
> committee seems to have suffered from an inferiority complex, and it
> seemed from my perspective that as fast as the PL/I committee chucked
> out toxic language, the BASIC committee adopted them.


There are two Basic standards as well: the smaller one came first.

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[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[Theodore Ts'o]

On Mon, Mar 13, 2023 at 12:00:04PM -0400, Paul Winalski wrote:
> 
> Note that the goal of a programming language standards committee is
> very different from the goal of those who use the language.  The
> committee's goal is to standardize existing practice of the language
> in a way that is implementable on the widest range of hardware and OS
> platforms, and to provide a controlled way to add language extensions.

It's worse than that.  Programming language stanrds committees are
dominated by engineers working on compilers, and there are very few (I
personally know of only one) OS engineers who might be trying to *use*
the language in a kernel where you have interrupt handlers, etc., and
don't like the fact that the compiler might optimize the code in such
a way that it moves instructions out from a critical region, etc.

> The advantage of programming in strict ISO C is that the resulting
> code will run just about anywhere.  If you don't care about that (and
> I'd wager most programmers don't) then ignore the standard.

For a sufficiently important program, it's possible for the authors to
say --- the C standard is just ***insane*** and if you want us to
support compilation of say, the Linux kernel by your compiler, you
*must* provide knobs to turn off certain insane "features" of the C
language spec.  GCC and Clang have those knobs, so you could say that
it they support the Linux kernel "dialect".  And the fact that this
dialect isn't blessed by the ISO committee doesn't cause me to lose
any sleep at night.

> As someone pointed out, the three things that most programmers value
> are execution speed, execution speed, and execution speed.  Aliasing
> issues greatly hamper what a modern optimizing compiler can do and
> still generate semantically correct code.

Compiler companies who are playing benchmark wars care about execution
speed --- of benchmark programs.  I'm not sure how many programmers
actually care about some of these optimizations, because there aren't
*that* many programs that are really CPU bound, and many which appear
to be CPU bound are often hitting memory bandwidth / caching issues,
which are not necessarily the things which tricky compiler
optimizations can fix.

As an OS engineer, I deeply despise these optimization tricks, since I
personally I care about correctness and not corrupting user data far
more than I care about execution speed ---- especially when the parts
of the kernel I work on tend not to be CPU bound in the first place.

	    	     	     	      	 - Ted

[TUHS] Re: [TUHS]: C dialects (was: I can't drive 55: "GOTO considered harmful" 55th anniversary)

[G. Branden Robinson]

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At 2023-03-13T22:49:23-0400, Theodore Ts'o wrote:
> As an OS engineer, I deeply despise these optimization tricks, since I
> personally I care about correctness and not corrupting user data far
> more than I care about execution speed ---- especially when the parts
> of the kernel I work on tend not to be CPU bound in the first place.

Alex has heard me say this before.

In the U.S., civilian air traffic controllers have a maxim.

Safe, orderly, efficient.[1]

You meet these criteria in order from left to right, and you satisfy one
completely, or to some accepted, documented, and well-known standard
measure, before you move on to the next.  The obvious reason for this is
that when aircraft meet each other at cruise altitudes, many people die.

I haven't yet settled on a counterpart for software engineering that I
like, but the best stab at it I've come up with is this.

Comprehensible, correct, efficient.

Incomprehensible code is useless.[2][3]  Even code that is proven
correct by formal methods is fragile if human maintainers are defeated
by its esoteric expression.[4]  (And formal verification can't save you
from incorrect specification in the first place.)  Richard Feynman once
said something along the lines of, if there is any phenomenon in physics
that he can't successfully explain to an audience of freshmen, then we
don't really understand it yet.  We use subtle, complex tools to solve
problems only when we haven't worked out ways to overcome them with
simple, straightforward ones.  Before we surrender to the excuse of
irreducible complexity we must have valid, verifiable, peer-reproducible
evidence that we've reduced the complexity as far as known methods will
allow.

But I'm junior to most of the grognards are on this list, so I'm
half-expecting the Joe Pesci opening statement from _My Cousin Vinny_...

Regards,
Branden

[1] https://www.avweb.com/features/say-again-8air-traffic-chaos/
[2] Literally useless, especially once that something that "just works"
    is ported to a new context.  "The real problem is that we didn't
    understand what was going on either."
    https://www.bell-labs.com/usr/dmr/www/odd.html
[3] Except for constructing streams of self-lauding horse puckey before
    promotion committees comprised of people who themselves attained,
    and will further advance, their status predicated on the audacity of
    their horse puckey.
[4] And once something's _that_ solid, it may be time to consider
    etching it in silicon rather than primary or secondary storage.

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