Re: [Tinycc-devel] Implementation of '--' argument

[grischka]

On 17.04.2023 07:59, avih via Tinycc-devel wrote:

> What some random script tries or doesn't try to do is irrelevant.

In a case however where the script and the tcc to be used with it
were written by the same author at the same time, we probably better
assume that it actually did work.

As it seems the purpose was different though, i.e. the '--' once
was used with instant execution to separate tcc args from the
program's args.

See commit here (from almost exactly 20 years ago) where "--" then
was replaced by "-run" as it still exists.

https://repo.or.cz/tinycc.git/commitdiff/40987541dc683a13cef764aa33f5da21b2660817

> tcc should follow the spec and common practices.

... provided that these do make sense in tcc's own context.  In cases
it better shouldn't.

For example, not to support compilation of files such as -c.c is
not a problem as long as we assume that such files do not exist.

Other than that tcc currently does support these forms with -run:
   tcc options [files less one] -run last_file arguments
and also
   tcc "-run options" file arguments (for usage with "#!", see ex4.c)
and also
   tcc options files -run @ arguments

I'd consider the latter form still rather "unofficial" so we could
still replace it by

   tcc options files -run -- arguments

which might (or might not) look better, in some sense.

What do people think?

-- grischka

> Generally speaking, applications which respect the POSIX syntax
> guidelines should treat non-option-argument "--" as an indication
> that all further arguments are operands:
> - https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html
>
> It's important to note that according to these guidelines, the
> options always come before the operands. I.e. mixing of options and
> operands (like GNU getopt does with permutations) is not allowed.
>
> Therefore, the use of "--" is to indicate where the options end and
> the operands start, especially for the case where the first operand
> begins with "-".
>
> "grep" should indeed respect these guidelines, and "--":
> - https://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html
>
> However, there are exceptions, for instance "echo" should not
> respect these guidelines and instead treat all arguments as operands:
> - https://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
>
> (the fact that some implementations of "echo" deviate from the spec
> and allow options such as "-e" or "-n" is the reason for echo being
> considered non portable, and why "printf" is recommended instead)
>
> The "c99" utility, which should probably be considered the spec for
> tcc, has some exceptions with regards to the syntax guidelines:
> - https://pubs.opengroup.org/onlinepubs/9699919799/utilities/c99.html
>
> While it does not specifically mention "--", it does say that
> options and operands can be mixed, and some options should appear
> after [c-files] operands, such as the "-l" and "-L" options
> (check the synopsis).
>
> For that reason, allowing "--" to be used before c-filenames
> is a footgun, because then it's not possible to add "-l" or "-L"
> options as needed by the spec.
>
> The fact that gcc also doesn't recognize "--" is existing common
> practice as well.
>
> However, clang does recognize "--", and indeed, it rejects "-l"
> or "-L" if they appear after "--" and some c-filenames.
>
> As far as I can tell that's inconsistent with the "c99" POSIX spec.
>
> So there you go. The main point of this is that it's not obvious
> that tcc should respect "--" the same as some other utilities.
>
> - avih
>
> On Sunday, April 16, 2023, 11:44:24 PM GMT+3, certanan via Tinycc-devel 
> <tinycc-devel@nongnu.org> wrote:
>
>
> I understand. But then what role does the flag fulfil in this script?
> https://github.com/qemacs/qemacs/blob/master/qe.tcc
>
> - certanan
>
>  > I tried: gcc -- a.c
>  > and got:
>  > gcc: error: unrecognized command-line option '--'
>  >
>  > This is with prerelease of gcc 13.
>  > So gcc does not support this. Why would this be needed for tcc?
>  >
>  > Herman
>  >
>  > _______________________________________________
>  > Tinycc-devel mailing list
>  > Tinycc-devel@nongnu.org <mailto:Tinycc-devel@nongnu.org>
>  > https://lists.nongnu.org/mailman/listinfo/tinycc-devel
>
>
> _______________________________________________
> Tinycc-devel mailing list
> Tinycc-devel@nongnu.org <mailto:Tinycc-devel@nongnu.org>
> https://lists.nongnu.org/mailman/listinfo/tinycc-devel
>
>
> _______________________________________________
> Tinycc-devel mailing list
> Tinycc-devel@nongnu.org
> https://lists.nongnu.org/mailman/listinfo/tinycc-devel