[Bug driver/87769] GCC build from source uses headers and libraries from directories host machine.

[mte.zych at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87769

--- Comment #2 from Mateusz Zych <mte.zych at gmail dot com> ---
Hi Andrew ;)
Thanks for your reply.

You are right that, in order to create standalone GCC,
I need to provide C standard library,
because GCC can work with various C standard library implementations.
The GNU C Library (glibc) is just one implementation,
which is not always used (for example Android is using bionic).

To correct my script,
I changed it to download and compile binutils, glibc and gcc respectively:

    # GNU Binutils
    wget https://ftp.gnu.org/gnu/binutils/binutils-2.31.tar.gz
    tar -xvf binutils-2.31.tar.gz
    mv binutils-2.31 binutils-source
    mkdir binutils-build
    cd binutils-build
    ../binutils-source/configure --build=x86_64-linux-gnu \
                                 --host=x86_64-linux-gnu \
                                 --target=x86_64-linux-gnu \
                                 --prefix=$PWD/gcc \
                                 --disable-multilib \
                                 --disable-nls
    make -j 4
    make install
    cd ..

    # GNU C Library (glibc)
    wget https://ftp.gnu.org/gnu/glibc/glibc-2.28.tar.gz
    tar -xvf glibc-2.28.tar.gz
    mv glibc-2.28 glibc-source
    mkdir glibc-build
    cd glibc-build
    ../glibc-source/configure --build=x86_64-linux-gnu \
                              --host=x86_64-linux-gnu \
                              --target=x86_64-linux-gnu \
                              --prefix=$PWD/gcc \
                              --disable-multilib \
                              --disable-nls \
                              --disable-timezone-tools
    make -j 4
    make install
    cd ..

    # GCC
    wget https://ftp.gnu.org/gnu/gcc/gcc-8.2.0/gcc-8.2.0.tar.gz
    tar -xvf gcc-8.2.0.tar.gz
    mv gcc-8.2.0 gcc-source
    cd gcc-source
    ./contrib/download_prerequisites
    cd ..
    mkdir gcc-build
    cd gcc-build
    ../gcc-source/configure --build=x86_64-linux-gnu \
                            --host=x86_64-linux-gnu \
                            --target=x86_64-linux-gnu \
                            --prefix=$PWD/gcc \
                            --enable-languages=c,c++ \
                            --disable-multilib \
                            --disable-nls
    make -j 4
    make install
    cd ..

This improved things, in a sense that, in my simple C++ application compiled
using GCC build from source it includes only these headers from host machine:

 - /usr/include/asm-generic/errno-base.h
 - /usr/include/asm-generic/errno.h
 - /usr/include/linux/errno.h
 - /usr/include/x86_64-linux-gnu/asm/errno.h

However, header files from host machine are still being included!
This can be seen when listing include directories used by GCC build from
source:

     
/home/mzych/gcc/bin/../lib/gcc/x86_64-linux-gnu/8.2.0/../../../../include/c++/8.2.0
     
/home/mzych/gcc/bin/../lib/gcc/x86_64-linux-gnu/8.2.0/../../../../include/c++/8.2.0/x86_64-linux-gnu
     
/home/mzych/gcc/bin/../lib/gcc/x86_64-linux-gnu/8.2.0/../../../../include/c++/8.2.0/backward
      /home/mzych/gcc/bin/../lib/gcc/x86_64-linux-gnu/8.2.0/include
      /home/mzych/gcc/bin/../lib/gcc/x86_64-linux-gnu/8.2.0/include-fixed
 ---> /usr/local/include
      /home/mzych/gcc/bin/../lib/gcc/../../include
 ---> /usr/include/x86_64-linux-gnu
 ---> /usr/include

OK, maybe I'm completely wrong here, but I think that
it would be great to introduce to GCC a configuration option,
which would prevent GCC from using any headers and libraries from host machine.

In this configuration, GCC would simply return compilation error in
case where required header or library would not found
in its own directory tree.

BTW, I was searching for such an option, but I couldn't find it.
 - https://gcc.gnu.org/install/configure.html

Thanks, Mateusz