Re: [tcpdump] About HAVE_NO_PRINTF_Z

[Guy Harris via tcpdump-workers <tcpdump-workers () lists tcpdump org>]

> --- Begin Message ---
>
>
> From: Guy Harris <gharris () sonic net>
>
> Date: Wed, 11 Jan 2023 23:06:23 -0800
>
> On Jan 11, 2023, at 10:44 PM, Francois-Xavier Le Bail via tcpdump-workers <tcpdump-workers () lists tcpdump org> wrote:
>
> > The commit fbd44158e0d5e6bb0c9b05671f702ebcf68cc56d was:
> > -------------------------------------------------------------------------------
> >    Mend "make check" on Solaris 9 (Autoconf only).
> >
> >    Sun C 5.9 does not support C99. GCC 4.6.4 recognizes -std=gnu99, but
> >    does not support the z length modifier in printf(3). In either case 18
> >    tests fail in the following manner:
> >
> >    <     [...]: domain [length 0 < 12] (invalid)
> >    ---
> >    >     [...]: domain [length 0 < zu] (invalid)
> >
> >    Make these tests conditional and disable them when HAVE_NO_PRINTF_Z is
> >    defined. Modify the Autoconf leg of the build process to define the
> >    macro when printf() does not handle %zu as expected. The CMake leg looks
> >    broken on Solaris 9 with 2.8.9 now, so leave it be for now.
> > -------------------------------------------------------------------------------
> >
> > I think that if a compiler builds a tcpdump that outputs "zu" when it must output "12", it's an error and this 
> > compiler must be tag "unsupported".
>
> It's probably more the library - %z is interpreted by the library at run time, not by the compiler at compile time 
> (except to the extent that the compiler does format/argument checking).
>
> On UN*Xes, the C library is typically the system API library, so it's bundled with the OS rather than the compiler, so 
> I don't know whether this is an issue of Sun C 5.9 or SunOS 5.9 (the core OS part of Solaris 9).
>
> Unfortunately, I'm not sure to what extent either autoconf's "is C99 supported?" or CMake's "is C99 supported?" can, or 
> does, check for library support, and various "I want C99" flags to the compiler may affect which version of the 
> language the compiler accepts and supports but it might not guarantee that the library with which the program will be 
> linked supports that version of the language.
>
> But it might make sense to just say "%z" is required by current versions of tcpdump (and libpcap), even if the lack of 
> that support can't be discovered until "zu" shows up in output, as long as we don't have to worry about older OS 
> versions if printf-formatting routines are part of an OS library rather than a C compiler support library.
>
> --- End Message ---
_______________________________________________
tcpdump-workers mailing list
tcpdump-workers () lists tcpdump org
https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers