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Re: An example: code to list exports of a Windows DLL.

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On 20/08/2019 23:59, Keith Thompson wrote:
> David Brown <david.brown@hesbynett.no> writes:
>> On 20/08/2019 11:18, Keith Thompson wrote:
>>> David Brown <david.brown@hesbynett.no> writes:
>>>> On 20/08/2019 03:31, Keith Thompson wrote:
>>>>> "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> writes:
>>>>>> On 19.08.2019 21:44, Richard wrote:
>>>>>>> "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> spake the secret code
>>>>>>> <qi042o$if8$1@dont-email.me> thusly:
>>>>>>>
>>>>>>>> The $ things in the following code are macros from the specified
>>>>>>>> header-only library on GitHub.
>>>>>>>
>>>>>>> Can you tell me where in the standard it allows for $ to be part of an
>>>>>>> identifier?
>>>>>>>
>>>>>>> I'm looking at 5.10 in N4659 (Draft C++17) and don't see it.
>>>>>>
>>>>>> In the future you might risk that people think you're a total novice,
>>>>>> one who doesn't even know the basics of identifiers in C++.
>>>>>
>>>>> Then I'll risk the same thing.  Can you explain where C++17 permits $
>>>>> in identifiers (or where it permits compilers to permit it)?
>>>>
>>>> It doesn't.
>>>>
>>>>> I believe that both foo$bar and foo\u0024bar violate a diagnosable rule
>>>>> and therefore require a diagnostic from any conforming compiler (which
>>>>> implies that gcc is non-conforming).
>>>>
>>>> You get the warning with "-Wpedantic" and an appropriate "-std" C++ 
>>>> standard (and perhaps an appropriate version of gcc).
>>>
>>> Can you demonstrate that?  I haven't been able to do so, with several
>>> versions of g++ (up to and including a bleeding-edge version I built
>>> from source a week and a half ago).  Here's the test case I used:
>>>
>>> #include <iostream>
>>> int main() {
>>>     const int foo$bar = 42;
>>>     std::cout << foo$bar << "\n";
>>> }
>>>
>>> compiled with "g++ -Wpedantic -std=c++17".  No warning from any version
>>> I have on my system.
>>>
>>
>> I was playing on <https://godbolt.org>, with just:
>>
>> 	int a$ = 1;
>>
>> "--std=c++03  -Wpedantic" gives a warning (testing with gcc trunk).
>> --std=c++11 and --std=c++17 do not.  (C++98 also warns.)
> 
> All editions of the C++ standard allow universal-character-names in
> identifiers, and all restrict them to ranges listed in a table (the
> table does not include the code for '$').
> 
> C++11 (and apparently C++14) add the "other implementation-defined
> characters" wording, which means that a compiler *may* permit '$' in
> identifiers (and needn't warn about it).  C++17 dropped it according to
> the drafts I have.
> 
> As far as I can tell, no version of g++ warns about '$' in an identifier
> with "-Wpedantic -std=c++17".  My reading of the C++17 standard is that
> such a warning is required, making g++ non-conforming.
> 
> It appears that gcc warns about '$' in identifiers with -std=c++98 and
> -std=c++03, and does not warn with -std=c++11 or higher.  It looks like
> the gcc maintainers responded to the addition of "other
> implementation-defined character" in C++11, but did not respond to its
> removal in C++17.
> 

I wonder if the change in C++17 was with a view to future uses of $ for
other purposes in C++ (such as for metaclasses)?  Has the status here
changed in C++20 ?


> clang supports '$' in identifiers as an extension, but always warns
> about them with "-std=c++... -Wpedantic", which is conforming behavior
> for all versions of the standard.
> 
> [...]
> 
>> I have C11 and C++14 standards conveniently at hand, and both have
>> "other implementation-defined character" clauses.
>>
>> If C++17 does not have that, would a $ in an identifier constitute
>> undefined behaviour (since it is not defined in the standard), and
>> therefore a compiler can support it, or would it constitute a syntax
>> error (requiring a diagnostic for conformity) ?
> 
> It would be a violation of a *diagnosable rule*, requiring at least a
> warning.  I don't think it's a syntax error, but there's no required
> distinction between syntax errors and other kinds of diagnosable errors.
> 
> The rule it violates is in N4700 5.10 [lex.name] paragraph 1:
> 
>     Each universal-character-name in an identifier shall designate a
>     character whose encoding in ISO 10646 falls into one of the ranges
>     specified in Table 2.
> 
> ('$' is not in Table 2.)  That wording in the C standard would imply
> that the behavior is undefined (or that it's a "constraint violation",
> if it's in an explicitly marked constraint) but C++ [intro.compliance]
> says:
> 
>     The set of diagnosable rules consists of all syntactic and
>     semantic rules in this document except for those rules containing
>     an explicit notation that “no diagnostic is required” or
>     which are described as resulting in “undefined behavior”.
> 
> The effect is the same: a diagnostic is required.  (If the
> implementation chooses to produce an executable after printing the
> required diagnostic, I suppose the behavior is undefined by omission.)
> 

Thanks for filling out the details here.

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An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-02 03:36 +0200
  Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-02 11:22 +0200
  Re: An example: code to list exports of a Windows DLL. rick.c.hodgin@gmail.com - 2019-08-02 02:33 -0700
    Re: An example: code to list exports of a Windows DLL. "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-08-02 16:54 -0700
      Re: An example: code to list exports of a Windows DLL. "Chris M. Thomasson" <invalid_chris_thomasson_invalid@invalid.com> - 2019-08-02 19:09 -0700
  Now on Github; based ordinals in listing (Re: An example: code to list exports of a Windows DLL.) "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-02 20:20 +0200
  Re: An example: code to list exports of a Windows DLL. legalize+jeeves@mail.xmission.com (Richard) - 2019-08-19 19:44 +0000
    Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-20 02:12 +0200
      Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-19 18:31 -0700
        Re: An example: code to list exports of a Windows DLL. David Brown <david.brown@hesbynett.no> - 2019-08-20 08:42 +0200
          Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-20 02:18 -0700
            Re: An example: code to list exports of a Windows DLL. Ian Collins <ian-news@hotmail.com> - 2019-08-20 22:22 +1200
              Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-20 14:21 -0700
            Re: An example: code to list exports of a Windows DLL. David Brown <david.brown@hesbynett.no> - 2019-08-20 13:00 +0200
              Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-20 14:59 -0700
                Re: An example: code to list exports of a Windows DLL. David Brown <david.brown@hesbynett.no> - 2019-08-21 10:29 +0200
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-21 11:14 +0200
                Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-21 02:55 -0700
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-21 12:30 +0200
                Re: An example: code to list exports of a Windows DLL. David Brown <david.brown@hesbynett.no> - 2019-08-21 14:22 +0200
                Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-21 12:41 -0700
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-22 03:38 +0200
                Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-21 19:24 -0700
                Re: An example: code to list exports of a Windows DLL. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-21 23:21 -0400
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-22 06:01 +0200
                Re: An example: code to list exports of a Windows DLL. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-22 00:26 -0400
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-22 07:54 +0200
                Re: An example: code to list exports of a Windows DLL. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-22 09:08 -0400
                Re: An example: code to list exports of a Windows DLL. "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-22 19:37 +0200
                Re: An example: code to list exports of a Windows DLL. scott@slp53.sl.home (Scott Lurndal) - 2019-08-22 13:17 +0000
                Re: An example: code to list exports of a Windows DLL. David Brown <david.brown@hesbynett.no> - 2019-08-22 16:07 +0200
                Re: An example: code to list exports of a Windows DLL. Keith Thompson <kst-u@mib.org> - 2019-08-21 02:42 -0700
  Re: An example: code to list exports of a Windows DLL. Frederick Gotham <cauldwell.thomas@gmail.com> - 2019-08-20 04:09 -0700
    Re: An example: code to list exports of a Windows DLL. "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-08-20 17:24 -0700

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