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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Sun, 08 Sep 2024 15:12:03 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>
>>>> Specifications are an agreement between the supplier and the client.  The
>>>
>>> The problem here is that the C standard, seen as a contract, is unfair
>>> to the programmer, because it's so excruciatingly hard to write code
>>> that is guaranteed to be free from UB.
>>
>> For programs there is no conformance level "free from UB" in the C
>> standard.
>
>The C standard doesn't define any conformance "levels":  it defines
>the term "strictly conforming program", for its own convenience in
>defining the language;  it also defines the term "conforming
>program", for no apparent purpose at all.

It defines both terms in the section on "Conformance", so I take it
that both are there for defining the conformance of programs; you may
not consider them to be levels, but given that all "strictly
conforming programs" are also "conforming programs", it has the
feeling of conformance levels to me.

>In both cases however
>what is given are simply definitions;  there is no reason an
>interested party couldn't give a definition of some other term, for
>the purpose of identifying a class of C programs that have some
>particular property -- such as being free from undefined behavior --
>where membership in the class is completely determined by statements
>in the C standard, being used as a reference document.

Sure, but the C standard does not give such a definition, so the
"interested party" would cherry-pick from the C standard.

>> There are two conformance levels for programs:
>>
>> 1) A strictly conforming program shall use only those features of the
>>    language and library specified in this International Standard.
>>    This excludes all programs that terminate, including the "Hello,
>>    World" program.  [...]
>
>I don't know why you say this.  Which aspects of the definition for
>"strictly conforming program" do you think are violated by a typical
>'Hello, World' program?

A typical "Hello, World" program terminates, and as mentioned, no
terminating program can be strictly conforming, because it exercises
at least implementation-defined behaviour (e.g., look at section
7.22.4.4 of C11).

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>