Mark Wielaard <mjw(a)redhat.com> writes:
On Fri, 2015-04-03 at 10:28 +0200, Petr Machata wrote:
> - Detect C++ compiler in configure, add supporting infrastructure to
> eu.am.
Looks good. Two questions below, but not blockers. Just curious.
> index faf8add..f1d290b 100644
> --- a/config/eu.am
> +++ b/config/eu.am
> [...]
> %.os: %.c %.o
> if AMDEP
> + test -d $(DEPDIR)/$(*D) || mkdir $(DEPDIR)/$(*D)
> if $(COMPILE.os) -c -o $@ -fpic -DPIC -DSHARED -MT $@ -MD -MP \
> -MF "$(DEPDIR)/$*.Tpo" `test -f '$<' || echo
'$(srcdir)/'`$<; \
> then cat "$(DEPDIR)/$*.Tpo" >> "$(DEPDIR)/$*.Po"; \
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.
> +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.
Thanks,
Petr