gcc and libstdc++-V3 build later

[Jonathan Wakely]

On Wed, 6 Oct 2021, 18:22 Xi Ruoyao, <xry111@mengyan1223.wang> wrote:

> On Mon, 2021-10-04 at 23:23 +0100, Jonathan Wakely via Gcc-help wrote:
> > On Mon, 4 Oct 2021 at 22:03, Bill Cunningham via Gcc-help
> > <gcc-help@gcc.gnu.org> wrote:
> > >
> > > I have bee looking at the LFS project. www.linuxfromscratch.org and
> > > I
> > > find their instructions a bit difficult. But at one point there is a
> > > gcc
> > > compiler compiled and installed with the --disable-libstdcxx option.
> > > Later, you are supposed to go back to your build directory and
> > > install
> > > libstdc++. I am not asking anyone to go to linuxfromscratch and
> > > investigate it so I will explain as much as possible as I believe I
> > > need
> > > too.
> > >
> > >      This is compiling a "fake"cross compiler. Since everything is
> > > compiled from scratch, C++ libraries do not exist at the time of the
> > > first compilation. After glibc is built and installed, you go back
> > > to
> > > gcc and compile the libstdcxx libraries of gcc. Exactly how is that
> > > done?
> >
> > Exactly as it says at
> >
> https://www.linuxfromscratch.org/lfs/view/development/chapter05/gcc-libstdc++-pass1.html
>
> There is actually two ways for this.  One is our way in LFS, another is
> not to pass --disable-libstdcxx, but use "make all-gcc" and "make
> install-gcc" to install the compiler (without libstdc++) first.  Then,
> build and install libc.  Finally, go back to the gcc build directory,
> and run "make all" to build the parts depending on libc, which were not
> built with "make all-gcc".
>

Yes, that's what I do when testing cross compilers.



> AFAIK the second approach is often used by embedded developers (building
> for e.g. avr-gcc).  We use the first approach in LFS because we don't
> want to say something like "please keep the GCC building directory here,
> don't remove it like building other packages" in the book.
> --
> Xi Ruoyao <xry111@mengyan1223.wang>
> School of Aerospace Science and Technology, Xidian University
>