[Bug c++/109021] New: accept size parameter in extern C

[Bug c++/109021] New: accept size parameter in extern C

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

            Bug ID: 109021
           Summary: accept size parameter in extern C
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: muecker at gwdg dot de
  Target Milestone: ---

A problem I encounter sometimes when using newer C headers in C++ is
with functions that have array argument with a size parameter:

extern "C" void foo(int N, char buf[N]);

I think g++ should accept this in general or only for extern "C".

At least for 1D arrays this should be easy as it could simply ignore the size 
and only emit a diagnostic with -pedantic.

[Bug c++/109021] accept size parameter in extern C

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
extern "C" just changes the language linkage but does not change the language
which the declaration is written in.

[Bug c++/109021] accept size parameter in extern C

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

--- Comment #2 from Martin Uecker <muecker at gwdg dot de> ---
True. But we could still take it as a hint about where this is not useful to
users to diagnose this as an error.

[Bug c++/109021] accept size parameter in extern C

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

--- Comment #3 from Andreas Schwab <schwab@linux-m68k.org> ---
*** Bug 110920 has been marked as a duplicate of this bug. ***

[Bug c++/109021] accept size parameter in extern C

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

--- Comment #4 from Martin Uecker <muecker at gwdg dot de> ---

Sorry, how can an enhancement request that addresses a real C/C++ compatibility
problem be marked "resolved invalid" ?

[Bug c++/109021] accept size parameter in extern C

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Martin Uecker from comment #4)
> Sorry, how can an enhancement request that addresses a real C/C++
> compatibility problem be marked "resolved invalid" ?

Because GCC does like these days to add huge extensions to the C++ language.
Maybe you could bring this up to WG21 (C++ standards committee) as a paper
which fully thought out (and an implementation either GCC or clang as an open
source example). GCC might take that implementation and have it as an extension
...

[Bug c++/109021] accept size parameter in extern C

[muecker at gwdg dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109021

--- Comment #6 from Martin Uecker <muecker at gwdg dot de> ---

Note that I do not propose to add variably modified types to C++.  This would
indeed be a major extension.  I simply propose to ignore the size expressions
in C headers as a usability improvement.  My patch I have somewhere for this
are a couple lines of code.

I plan to bring this up to WG21 anyway, but standards should ideally
standardize things where there exists prior experience.  It would be helpful if
GCC takes part in this process.