Re: [lmi] [Bulk] Re: Cross-compiling lmi from Linux to MSW

[Greg Chicares]

On 2016-01-26 15:07, Vadim Zeitlin wrote:
> On Tue, 26 Jan 2016 04:29:56 +0000 Greg Chicares <address@hidden> wrote:
> 
> GC> On 2016-01-23 15:40, Vadim Zeitlin wrote:
> GC> >
> GC> >  I have a pending patch to lmi configure which adds flags for C++11
> GC> > support, I can post it if you'd like. But until then you indeed need to
> GC> > pass it configure manually, although I usually use it as part of CXX and
> GC> > not CXXFLAGS to ensure that it's used also for linking. I don't actually
> GC> > think it makes any difference under Linux, but it definitely does under 
> OS
> GC> > X (because C++11 uses a different standard library there) and so I just 
> do
> GC> > it consistency under all platforms.
> GC> 
> GC> Then for OSX, wouldn't it make sense to add it to LDFLAGS? Just curious.
> 
>  This works too, of course, but then you need to add it to two different
> places instead of only one. And, to be incredibly pedantic, in principle
> LDFLAGS could be used to link a C-only target, in which case -std=c++11
> would be out of place (although almost certainly still harmless).

I understand why the 'g++' driver is used as the linker for C++ programs
as a general rule. If, on OSX, you use something like 'g++ -std=c++11' to link,
then we have a g++_as_linker flag that can't be passed in CXXFLAGS or LDFLAGS.
Isn't that a design flaw in the gnu build system?

This isn't just pedantry: what if we don't know the name of the C++ compiler,
because it's deduced from '--host'? In this self-contained example...

cd ~/build/wxpdfdoc-msw
~/src/3rdparty/wxpdfdoc/configure \
  --prefix=$HOME/msw/i686-w64-mingw32 \
  --host=i686-w64-mingw32 \
  --with-wx-config=$HOME/msw/i686-w64-mingw32/bin/wx-config \
  CXXFLAGS='-std=c++11'
make $coefficiency install

...we don't define $(CXX) at all. The lmi makefiles presently do define it:

config_options = \
  --prefix=$(prefix) \
  --build=i686-pc-cygwin \
  --host=i686-w64-mingw32 \
  --disable-dependency-tracking \
  --with-wx-config=$(prefix)/bin/wx-config-portable \
       AR='$(mingw_bin_dir)/$(triplet_prefix)ar' \
       AS='$(mingw_bin_dir)/$(triplet_prefix)as' \
       CC='$(mingw_bin_dir)/$(triplet_prefix)gcc $(wx_cc_flags)' \
      CPP='$(mingw_bin_dir)/$(triplet_prefix)cpp' \
      CXX='$(mingw_bin_dir)/$(triplet_prefix)g++ $(wx_cxx_flags)' \
  DLLTOOL='$(mingw_bin_dir)/$(triplet_prefix)dlltool' \
       LD='$(mingw_bin_dir)/$(triplet_prefix)ld' \
...

but that seems to be a flaw (because $(triplet_prefix) has to be specified
for cross compiling, as we as for other reasons).

If you don't know what $(CXX) is, how do you add '-std=c++11' to it?

(Maybe that's why you're patching 'configure'.)