[Bug c/103810] New: -fallow-parameterless-variadic-functions flag could use a testcase that covers its documentation better

[Bug c/103810] New: -fallow-parameterless-variadic-functions flag could use a testcase that covers its documentation better

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103810

            Bug ID: 103810
           Summary: -fallow-parameterless-variadic-functions flag could
                    use a testcase that covers its documentation better
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: documentation
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: egallager at gcc dot gnu.org
                CC: gingold at adacore dot com
  Target Milestone: ---

So, I'm giving the GCC docs another read-through, and the
-fallow-parameterless-variadic-functions docs say:

"Accept variadic functions without named parameters. Although it is possible to
define such a function, this is not very useful as it is not possible to read
the arguments. This is only supported for C as this construct is allowed by
C++."

However, looking in the testsuite for where this flag is actually tested, I
only find gcc/testsuite/gcc.dg/va-arg-5.c which only has a single declaration
of the kind allowed by the flag. If the docs are correct that it is possible to
define such a function, and not just declare it, shouldn't there be a test for
a function definition to go with the declaration? Also, what are you supposed
to do with such a declaration/definition after you have it, if you can't read
the arguments? You can still call it even if you can't read the arguments,
can't you? Shouldn't the testcase test calling it, too, then?

(cc-ing person who added the option)

[Bug c/103810] -fallow-parameterless-variadic-functions flag could use a testcase that covers its documentation better

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103810

--- Comment #1 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Note also that there is a proposal for C23 (N2854) to allow such 
functions, including changing the requirements on va_start to make it 
possible to read their arguments.

[Bug c/103810] -fallow-parameterless-variadic-functions flag could use a testcase that covers its documentation better

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103810

--- Comment #2 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to joseph@codesourcery.com from comment #1)
> Note also that there is a proposal for C23 (N2854) to allow such 
> functions, including changing the requirements on va_start to make it 
> possible to read their arguments.

OK, but even if it becomes accepted as standard C in C23, I'm assuming the flag
would still stick around for previous standards?