Re: Using a different C++ Standard Library

[Ralf Wildenhues]

Hi Liviu,

* Liviu Nicoara wrote on Thu, Dec 15, 2005 at 08:32:23PM CET:
> 
> Since I posted the message I took the time to dig into the libtool
> script and the generated Makefiles looking for clues. I am afraid I do
> not have my exact original setup available for a cut&paste here but only
> an approximation:
> 
> configure.ac:
> -------------

*snip*
> AC_PROG_CXX(aCC,CC,g++)

The arguments to AC_PROG_CXX should be separated by spaces:
  AC_PROG_CXX([aCC CC g++])

I believe it searches all three of those by default though, so there's
no need to specify them.

> AC_PROG_LIBTOOL
> 
> AC_PROG_MAKE_SET(gmake)

I don't think this takes an argument at all.  If you want a different
make, do like this:
  ./configure MAKE=gmake
  gmake
  gmake install

> AM_PROG_AS
> 
*snip*

> AC_SUBST([MY_CXX_EXTRA_CPPFLAGS],[${MY_CXX_EXTRA_CPPFLAGS};])
> AC_SUBST([MY_CXX_EXTRA_LDFLAGS], [${MY_CXX_EXTRA_LDFLAGS};])
> AC_SUBST([MY_CXX_EXTRA_LIBS],    [${MY_CXX_EXTRA_LIBS};])

This can be reduced to just 
  AC_SUBST([MY_CXX_EXTRA_CPPFLAGS])
  ...

*snip*
> With this setup and invoking configure with the directory where stdlib
> is installed (--with-stdcxx=dir) I get what I posted previously.

OK.

> Please notice in my previous posting that the invocations of g++ had
> -nostdlib on the link line followed by a set of explicit link paths (-L)
> and the GNU C++ libraries.
> 
> I have a workaround - which along with the explicit change of CXX to gcc
> can probably be qualified as an 'orrible 'ack:  in order to link using
> gcc I place this line in my source/Makefile.am:
> 
> CXXLINK = $(LIBTOOL) --mode=link $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS)
> $(AM_LDFLAGS) $(LDFLAGS) -o $@
> 
> Please notice the missing --tag=CXX which accomplishes the goal.

The hack seems ok to me.  You could also use --tag=CC explicitly.

> In response to your suggestions for a fix, more valuable to me as a user
> would probably be an option to indicate I only want minimal C++ language
> support. How about no C++ support at all and allowing me to indicate all
> libraries I need?

Well, that is just what I meant with the third alternative:

> Ralf Wildenhues wrote:
> > 
> > Nope, your understanding is not flawed.  We need to implement a way to
> > specify:
> > - I want the C++ stdlib linked in
> > - I want (possibly) only minimal runtime lib linked in
> > - none of the above.

:-)

Cheers,
Ralf