> -----Original Message-----
> From: Richard Biener <richard.guent...@gmail.com>
> Sent: Tuesday, July 8, 2025 14:22
> To: Robert Dubner <rdub...@symas.com>
> Cc: Rainer Orth <r...@cebitec.uni-bielefeld.de>; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] cobol: Implement CXXFLAGS_FOR_COBOL.
>
> On Tue, Jul 8, 2025 at 12:46 AM Robert Dubner <rdub...@symas.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Rainer Orth <r...@cebitec.uni-bielefeld.de>
> > > Sent: Monday, July 7, 2025 18:08
> > > To: Robert Dubner <rdub...@symas.com>
> > > Cc: gcc-patches@gcc.gnu.org
> > > Subject: Re: [PATCH] cobol: Implement CXXFLAGS_FOR_COBOL.
> > >
> > > Hi Robert,
> > >
> > > > I have elsewhere described my frustration in trying, during
> > development,
> > > > to set more stringent error-finding and warning-generating
> compilation
> > > > options. But they seem to require the use of CXXFLAGS, which in at
> > > least
> > > > the case of trying to set -std=c++14, causes libcody's compilation
> to
> > > > fail, since it wants, specifically c++11.
> > > >
> > > > So, I dove in and figured out how to implement CXXFLAGS_FOR_COBOL.
> > This
> > > > new flag applies only to compilations of c++ programs in the
> gcc/cobol
> > > > source code tree.
> > > >
> > > > These changes were tested with a bootstrap build of
> > > > --enable-languages=c,c++,fortran,cobol.
> > > >
> > > > Is this okay for trunk?
> > >
> > > I think there's a far easier way which doesn't require any patch.
> Have
> > > a look at toplevel configure.ac:
> > >
> > > # When bootstrapping with GCC, build stage 1 in C++14 mode to ensure
> > that
> > > a
> > > # C++14 compiler can still start the bootstrap. Otherwise, if
> building
> > > GCC,
> > > # require C++14 (or higher).
> > > if test "$enable_bootstrap:$GXX" = "yes:yes"; then
> > > CXX="$CXX -std=c++14"
> > > elif test "$have_compiler" = yes; then
> > > AX_CXX_COMPILE_STDCXX(14)
> > >
> > > if test "${build}" != "${host}"; then
> > > AX_CXX_COMPILE_STDCXX(14, [], [], [_FOR_BUILD])
> > > fi
> > > fi
> > >
> > > You should be able to achieve what you want by building with CXX='g++
> > > -std=c++14', just as one can build a 32-bit gcc with a 64-bit host
> > > compiler using CXX='g++ -m32'.
> >
> > In this case, although I reported my patch works with a bootstrap build,
> I
> > need it to work with an --disable-bootstrap build. I did the bootstrap
> > just to make sure I hadn't broken something. I anticipate using
> > CXXFLAGS_FOR_COBOL during development.
> >
> > When I try
> >
> > CXX=banana ../configure ... & make ...
>
> For me:
>
> obj> CXX=banana ~/src/gcc/configure --disable-bootstrap
> configure: loading site script /usr/share/site/x86_64-unknown-linux-gnu
> checking build system type... x86_64-pc-linux-gnu
> checking host system type... x86_64-pc-linux-gnu
> checking target system type... x86_64-pc-linux-gnu
> checking for a BSD-compatible install... /usr/bin/install -c
> checking whether ln works... yes
> ...
> checking whether banana supports C++14 features by default... no
> checking whether banana supports C++14 features with -std=gnu++14... no
> checking whether banana supports C++14 features with -std=gnu++1y... no
> checking whether banana supports C++14 features with -std=c++14... no
> checking whether banana supports C++14 features with +std=c++14... no
> checking whether banana supports C++14 features with -h std=c++14... no
> checking whether banana supports C++14 features with -std=c++1y... no
> checking whether banana supports C++14 features with +std=c++1y... no
> checking whether banana supports C++14 features with -h std=c++1y... no
> configure: error: *** A compiler with support for C++14 language
> features is required.
>
> so setting CXX definitely makes a difference even with --disable-
> bootstrap.
>
> It seems libcody alters CXX to force -std=c++11 but as CXXFLAGS comes
> after it when you add -std=c++14 to it it will break.
>
> So using CXX="g++ -std=c++14" should do the trick. You do not need to
> re-specify that at make time. It works for me and builds libcody just
> fine.
I agree that
CXX=banana ../configure
fails quickly regardless of any other configure parameters. I don't know
what I did wrong that led me to suggest otherwise.
This apparently does provide a solution for -std=c++14, one that does an end
run around the problems that show up with
CXXFLAGS="-std=c++14"
although I have to wonder why that's not regarded as a problem.
But I have other requirements. I apologize if I keep repeating myself, but
I am being forced to.
I want to be able to, for example,
CXXFLAGS='-ggdb -O0' CXXFLAGS_FOR_COBOL="-Wsomething_or_other"
../configure
....
I want those warnings to apply to gcc/cobol and not to anything else.
And then, later on, I want to be able to
make CXXFLAGS_FOR_COBOL="-Wreplacement_warnings"
<shrug> I can't do that with the CXXFLAGS= or CXX= solutions.
>
> Richard.
>
> > and
> > make CXX=banana
> >
> > in both cases, the build succeeds. The "CXX=banana" seems to do nothing
> > when --disable-bootstrap is active.
> >
> > For a bootstrap build, the configure fails quickly:
> >
> > checking whether banana supports C++14 features by default... no
> >
> > Furthermore, even if this method did work, I need the CXXFLAGS_FOR_COBOL
> > options to appear at the end of the list, not the beginning, since they
> > may need to override what came before.
> >
> > So, my request for agreement to apply the patch stands.
> >
> > >
> > > Rainer
> > >
> > > --
> > >
> > ------------------------------------------------------------------------
> --
> > > ---
> > > Rainer Orth, Center for Biotechnology, Bielefeld University
