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

[avih]

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

tcc should follow the spec and common practices.

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
> https://lists.nongnu.org/mailman/listinfo/tinycc-devel

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