Re: [Qemu-devel] Buildbot failure: MinGW

[Thomas Huth]

On Wed, 19 Feb 2014 11:53:09 +0000
Peter Maydell <address@hidden> wrote:

> On 19 February 2014 04:27, Stefan Weil <address@hidden> wrote:
> > Hi Gerd, hi Stefan,
> >
> > we now need a C++ compiler on the buildbots. Currently, it's missing for
> > MinGW:
> >
> > /bin/sh: i686-pc-mingw32-g++: command not found
> 
> Don't we successfully fall back to "don't build C++ things" if
> configure doesn't detect the C++ compiler?

I recently had a similar problem compiling QEMU on a freshly installed
system, where I only had a normal C compiler, but no C++ installed yet.

In rules.mak, you can find these lines:

 # If we have a CXX we might have some C++ objects, in which case we
 # must link with the C++ compiler, not the plain C compiler.
 LINKPROG = $(or $(CXX),$(CC))

So that's ok, it sets LINKPROG to the c++ compiler if the variable is
set, and to the C compiler if not.

But now have a look at the configure script:

 if test -z "${CXX}${cross_prefix}"; then
   cxx="c++"
 else
   cxx="${CXX-${cross_prefix}g++}"
 fi

 [...]

 echo "CXX=$cxx" >> $config_host_mak

That seems to always set the CXX variable! I think the above
if-statement is wrong, it should set cxx only if the c++ program is
really available.

 Thomas