Wireshark mailing list archives

Re: Allowing use of more C99 features


From: Graham Bloice <graham.bloice () trihedral com>
Date: Fri, 2 Sep 2016 09:17:17 +0100

On 2 September 2016 at 09:03, Paul Offord <Paul.Offord () advance7 com> wrote:

Allowing the use of // for comments would be really useful as VS has a
handy button for commenting out selected code and it prefixes each line
with //




Like all decent editors should do.  For VS the keyboard combo is Ctrl + K,
Ctrl + C.  Use Ctrl + K, Ctrl + U.






*From:* wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces@
wireshark.org] *On Behalf Of *Graham Bloice
*Sent:* 02 September 2016 08:54
*To:* Developer support list for Wireshark <wireshark-dev () wireshark org>
*Subject:* Re: [Wireshark-dev] Allowing use of more C99 features







On 2 September 2016 at 03:51, Guy Harris <guy () alum mit edu> wrote:

On Sep 1, 2016, at 1:14 PM, Peter Wu <peter () lekensteyn nl> wrote:

Patch https://code.wireshark.org/review/17421 will allow use of some C99
features in master (future 2.4):

For UN*X, with autotools:

        The AC_PROG_CC_C99 macro is used, and, if it fails to enable what
it considers "C99 mode" for the compiler, the configure script will fail.
This means some older compilers may not be supported; it's probably time to
drop those compilers.  The macro appears to try to enable it for:

                GCC (and Clang), using -std=gnu99
                IBM XL C, using -qlanglvl=extc99
                HP cc, using -AC99
                Intel ICC, using -std=c99
                SGI's C compiler for IRIX, using -c99
                Sun/Oracle's C compiler, using -xc99=all
                DEC/Compaq/HP's C compiler for Alpha on Tru64, using -c99

        so you're out of luck if you have a version of those compilers
that doesn't support those flags and doesn't support all of:

                _Bool, // comments, flexible array members, inline, signed
and unsigned long long int, mixed code and declarations, named
initialization of structs, restrict, va_copy, varargs macros, variable
declarations in for loops, and variable length arrays

For UN*X, with CMake:

        I'm not sure whether it'll properly enable C99 support for all of
the compilers in question.

For Windows (CMake assumed), MSVC 2013 supports:

        // comments as long as you don't compile with /Za, but there might
be a warning to suppress;

        flexible arrays, but there's a warning to suppress, which this
change suppresses;

        inline functions - it might require __inline rather than inline,
but GLib is #defining inline to be __inline with MSVC, so we can just use
"inline";

        mixed code and declarations, but there's a bug that might or might
not hit us:

                https://connect.microsoft.com/
VisualStudio/feedback/details/808650/visual-studio-2013-c99-compiler-bug



That particular example seems to have been fixed, at least for me with
VS2013 Update 5.



        named initialization of structs, but there's a bug that might or
might not hit us:

                https://connect.microsoft.com/
VisualStudio/feedback/details/805981



That particular example seems to have been fixed, at least for me with
VS2013 Update 5.





        varargs macros, which we're already using;

        variable declarations in for loops, apparently:

                http://stackoverflow.com/questions/21696983/error-on-
declaring-variable-in-for-statement

so, in addition to

- flexible array members
- trailing comma in enum declarations
- inline function keyword

we also can use // comments and, apparently, variable declarations in for
loops, assuming there's no bug that gets in the way.  *If* we avoid the
bugs, we can also use mixed code and declarations and named initialization
of structs.






--

Graham Bloice

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-- 
Graham Bloice
Software Developer
Trihedral UK Limited
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