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Re: [PATCH 1/2] Enable C++


On Fri, 2015-04-03 at 23:40 +0200, Petr Machata wrote:
> Mark Wielaard <mjw@redhat.com> writes:
> > Why is that mkdir now necessary?
> 
> It's not, but I thought it's a good idea for symmetry.  The reason the
> c++ bits need this mkdir is that we keep that code in a sub-directory,
> and this creates the corresponding sub-directory for the dependency
> tracking helper files.

Aha, ok thanks.

> >> +AC_CACHE_CHECK([for working C++ compiler], ac_cv_cxx_works,
> >> +[AC_LANG_PUSH([C++])
> >> + AC_COMPILE_IFELSE([AC_LANG_SOURCE([dnl
> >> +struct foo {
> >> +  int i;
> >> +  explicit foo () : i (0) {}
> >> +  virtual ~foo () {}
> >> +};])], ac_cv_cxx_works=yes, ac_cv_cxx_works=no)
> >> + AC_LANG_POP()])
> >> +AM_CONDITIONAL(HAVE_CXX, test "$ac_cv_cxx_works" = yes)
> >
> > We require gnu++98 above.
> > Is the explicit enough to make sure the compiler supports C++98?
> 
> Well, this is a C++98 code.  It's of course not enough to test the whole
> C++98--the language is vast.  The reason for that test is that I want to
> make sure we really do have a C++ compiler.  AC_PROG_CXX happily exports
> CXX even if none is available, so we can't use that in conditionals.

I was mostly wondering whether we needed to add an command line argument
like -std=gnu++98 to be sure. But maybe that is all implicit and
standard for all gcc versions anyway.

Cheers,

Mark

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