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Re: Cake - C23 to C99 transpiler

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Bart <bc@freeuk.com> writes:
> [...]
>
>> Also, gcc gets away with allowing $ by default;  tcc generally copies
>> gcc in terms of how a compiler is invoked, so this surprisingly goes
>> against that.
>
> gcc allowing $ in identifiers is a documented extension for most
> targets, so it doesn't warn about them even with "-pedantic".  One could
> argue that this isn't necessarily an "extension", since "other
> implementation-defined characters" are explicitly permitted by C11
> 6.4.2.1.
>
> Interestingly, the C23 draft doesn't have that wording.  Instead, it
> allows XID_Start and XID_Continue characters, so it expands the set of
> characters that *all* implementations must support,

I believe that conclusion is not correct.  The C23 draft n3047 says
this:

    An XID_Start character is an implementation-defined character
    whose corresponding code point in ISO/IEC 10646 has the
    XID_Start property.  An XID_Continue character is an
    implementation-defined character whose corresponding code point
    in ISO/IEC 10646 has the XID_Continue property.

The presence of the modifying adjective "implementation-defined" in
both cases surely means, at the very least, that implementations
are allowed to subset the Unicode-specified XID_Start/XID_Continue
sets with regard to what characters are allowed in identifiers.


> but doesn't permit '$' (assuming '$' isn't in XID_Start or
> XID_Continue).

I'm not sure this statement is right either (and agreeing with the
assumption that '$' is not in XID_Start or XID_Continue).  The
Unicode reference documentation is so bad that I can't make out
with any degree of certainty whether it allows various domains to
extend the XID_Start/XID_Continue sets for the application in
question.  The presence of "implementation-defined" further muddies
the waters.  To be clear, neither am I saying that I think the
statement is wrong;  only that at present there is not enough
information to be confident of either conclusion.


> A conforming C23 implementation can still accept '$' in identifiers
> as an extension, but my understanding is that it must issue a
> warning.

If accepting '$' is only an extension, and not a consequence of
some implementation-defined behavior, then using '$' in an
identifier results in a syntax error, which requires a diagnostic.
Where is the uncertainty?


> In any case, as of C11 a conforming C compiler is not required to accept
> '$' in identifiers *at all*, even with a command-line option, and may
> reject any program that uses it.  You can of course choose to rely on
> the behavior of specific compilers, but if you use '$' in identifiers
> then your code is not 100% portable.  (REMINDER:  "not 100% portable" is
> not necessarily a criticism.)

Yes.

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Thread

Cake -  C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-08-18 18:44 -0700
  Re: Cake - C23 to C99 transpiler Blue-Maned_Hawk <bluemanedhawk@example.invalid> - 2022-09-06 02:48 -0400
    Re: Cake - C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-09-06 10:08 -0700
      Re: Cake - C23 to C99 transpiler Vir Campestris <vir.campestris@invalid.invalid> - 2022-09-07 12:27 +0100
        Re: Cake - C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-09-07 05:45 -0700
          Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-07 15:35 +0100
            Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 16:38 +0100
              Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-07 17:04 +0100
                Re: Cake - C23 to C99 transpiler Anton Shepelev <anton.txt@g{oogle}mail.com> - 2022-09-07 19:14 +0300
                Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 17:31 +0100
                Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-07 17:40 +0100
                Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 17:49 +0100
                Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-07 19:27 +0100
                Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 20:02 +0100
                Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-07 21:03 +0100
                Re: Cake - C23 to C99 transpiler Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-07 13:52 -0700
                Re: Cake - C23 to C99 transpiler Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-14 07:14 -0700
                Re: Cake - C23 to C99 transpiler Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-14 10:59 -0700
                Re: Cake - C23 to C99 transpiler Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-15 23:46 -0700
                Re: Cake - C23 to C99 transpiler David Brown <david.brown@hesbynett.no> - 2022-09-07 20:17 +0200
                Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 19:58 +0100
                Re: Cake - C23 to C99 transpiler Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-07 13:26 -0700
                Re: Cake - C23 to C99 transpiler Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-07 23:42 +0100
                Re: Cake - C23 to C99 transpiler Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-14 06:45 -0700
                Re: Cake - C23 to C99 transpiler Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-14 06:40 -0700
                Re: Cake - C23 to C99 transpiler Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-07 10:28 -0700
                Re: Cake - C23 to C99 transpiler David Brown <david.brown@hesbynett.no> - 2022-09-07 20:05 +0200
            Re: Cake - C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-09-07 15:28 -0700
              Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-08 00:51 +0100
                Re: Cake - C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-09-08 05:20 -0700
                Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-08 16:41 +0100
                Re: Cake - C23 to C99 transpiler scott@slp53.sl.home (Scott Lurndal) - 2022-09-08 16:43 +0000
                Re: Cake - C23 to C99 transpiler Bart <bc@freeuk.com> - 2022-09-08 19:23 +0100
                Re: Cake - C23 to C99 transpiler Thiago Adams <thiago.adams@gmail.com> - 2022-09-08 09:59 -0700

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