Re: -W options to gcc

[Guy Harris <guy () alum mit edu>]

On Mar 28, 2013, at 5:02 PM, Guy Harris <guy () alum mit edu> wrote:

> On Mar 28, 2013, at 4:41 PM, Michael Richardson <mcr () sandelman ca> wrote:
>
> > > > > > > "Guy" == Guy Harris <guy () alum mit edu> writes:
> >   Guy> Wireshark's configure script checks whether the GCC shell
> >   Guy> variable is "yes" or the CC shell variable is "clang" and, if
> >   Guy> true, sets a flag saying "this compiler supports -W options". 
> >
> > Cooll.. can we copy and paste :-)
>
> Wireshark's configuration scripts are GPLed, along with the rest of Wireshark, so, in principle, that might be a 
> problem.
>
> I didn't originally write that macro, so I can't just relicense it.

...and it's been a while since I looked at it, so I had to reimplement it from scratch, which eliminates the licensing 
issues.

So I've checked in changes to tcpdump and libpcap's configure scripts that add a macro to check whether the compiler 
supports a particular flag, and, if the .devel file is present, uses that to decide whether to add various -W flags.  
(It doesn't bother checking whether the compiler is GCC or not, nor does it explicitly check for clang; the easiest way 
to compile with clang on OS X is --without-gcc, which means you end up compiling with "cc", not "clang".)

We can use that to add some more -W flags to libpcap and tcpdump.  The ones that have been suggested are:

        -Wunused -Wunused-parameter - you suggested those;

        -W along with -Wno-unused-but-set-variable -Wno-unused-function -Wno-strict-aliasing - Gisle suggested those 
(tcpdump, but not libpcap, is built with -W).

It should probably also do a test to see whether the compiler supports -M and do the dependency-generation stuff iff 
.devel is present and the compiler supports -M, so that

        1) you can create .devel if you have a compiler that doesn't support -M for dependency generation

and

        2) if you have .devel, the dependency generation will be done if the compiler supports -M, regardless of 
whether it's GCC or not.
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