Re: [PATCH 2/3] configure: Fix building with SASL on Windows

[Philippe Mathieu-Daudé]

On 3/9/20 10:57 AM, Daniel P. Berrangé wrote:
> On Sat, Mar 07, 2020 at 06:22:21PM +0100, Philippe Mathieu-Daudé wrote:
> > The Simple Authentication and Security Layer (SASL) library
> > re-defines the struct iovec on Win32 [*]. QEMU also re-defines
> > it in "qemu/osdep.h". The two definitions then clash on a MinGW
> > build.
> > We can avoid the SASL definition by defining STRUCT_IOVEC_DEFINED.
> > Add the definition to vnc_sasl_cflags if we are uing MinGW.
> >
> > [*] 
> > https://github.com/cyrusimap/cyrus-sasl/blob/cyrus-sasl-2.1.27/include/sasl.h#L187
> >
> > Cc: Alexey Pavlov <address@hidden>
> > Cc: Biswapriyo Nath <address@hidden>
> > Cc: Youry Metlitsky <address@hidden>
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >   configure | 8 +++++++-
> >   1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/configure b/configure
> > index 0c2dd1eb08..0bc87ce42a 100755
> > --- a/configure
> > +++ b/configure
> > @@ -3375,7 +3375,13 @@ if test "$vnc" = "yes" && test "$vnc_sasl" != "no" ; then
> >   int main(void) { sasl_server_init(NULL, "qemu"); return 0; }
> >   EOF
> >     # Assuming Cyrus-SASL installed in /usr prefix
> > -  vnc_sasl_cflags=""
> > +  if test "$mingw32" = "yes" && test "$iovec" != "yes"; then
>
> I don't get why we need the "iovec != yes" check there ?
>
> On mingw sys/uio.h doesn't exist, so "$iovec" will always
> be "no", and so this conditional is equivalent to
>
>     if test "$mingw32" = "yes; then

Indeed.

> If for some strange reason, a future Windows adds sys/uio.h
> header containing struct iovec, then QEMU won't define its
> own local copy if struct iovec, and so "$iovec" will be "yes".
>
> In this situation we don't want SASL to define its struct iovec
> either.
>
> IOW we need -DSTRUCT_IOVEC_DEFINED no matter what $iovec value
> is AFAICT.

Way simpler!

> This would mean the previous patch is redundant too.

Yes, thanks for reviewing :)

> > +    # QEMU defines struct iovec in "qemu/osdep.h",
> > +    # we don't want libsasl to redefine it in <sasl/sasl.h>.
> > +    vnc_sasl_cflags="-DSTRUCT_IOVEC_DEFINED"
> > +  else
> > +    vnc_sasl_cflags=""
> > +  fi
> >     vnc_sasl_libs="-lsasl2"
> >     if compile_prog "$vnc_sasl_cflags" "$vnc_sasl_libs" ; then
> >       vnc_sasl=yes
>
> Regards,
> Daniel