Install GCC 9 on Raspberry Pi and build C++17 programs

commands.sh

# Commands used in the video https://youtu.be/-bCG87jBDqA :

sudo apt update && sudo apt upgrade -y

git clone https://bitbucket.org/sol_prog/raspberry-pi-gcc-binary.git
cd raspberry-pi-gcc-binary
tar -xjvf gcc-9.1.0-armhf-raspbian.tar.bz2
sudo mv gcc-9.1.0 /opt
cd ..
rm -rf raspberry-pi-gcc-binary

cd ~
echo 'export PATH=/opt/gcc-9.1.0/bin:$PATH' >> ~/.bashrc
echo 'export LD_LIBRARY_PATH=/opt/gcc-9.1.0/lib:$LD_LIBRARY_PATH' >> ~/.bashrc
. ~/.bashrc
sudo ln -s /usr/include/arm-linux-gnueabihf/sys /usr/include/sys
sudo ln -s /usr/include/arm-linux-gnueabihf/bits /usr/include/bits
sudo ln -s /usr/include/arm-linux-gnueabihf/gnu /usr/include/gnu
sudo ln -s /usr/include/arm-linux-gnueabihf/asm /usr/include/asm
sudo ln -s /usr/lib/arm-linux-gnueabihf/crti.o /usr/lib/crti.o
sudo ln -s /usr/lib/arm-linux-gnueabihf/crt1.o /usr/lib/crt1.o
sudo ln -s /usr/lib/arm-linux-gnueabihf/crtn.o /usr/lib/crtn.o

g++-9.1 -std=c++17 -Wall -pedantic test_fs.cpp -o test_fs
./test_fs

test_fs.cpp

// Build/compile with:
// g++-9.1 -std=c++17 -Wall -pedantic test_fs.cpp -o test_fs
#include <iostream>
#include <filesystem>

int main() {
    for(auto &file : std::filesystem::recursive_directory_iterator("./")) {
        std::cout << file.path() << '\n';
    }
}

So I did a complete test, I installed the latest Rasperry Pi OS 32 bits Lite, did an upgrade & update, followed exactly the procedure described in the linked article and now I'm able to build C++ programs with GCC 10.1.

I have tripple checked, and followed the steps for 9.1.0 version first, only then tried 10.1.0 when the 9.1.0 didn't work..

additionally, tried the link you've just provided me with - i have exactly the same error:

pi@bo100nka-pi:~ $ g++-10.1 -std=c++17 -Wall -pedantic if_test.cpp -o if_test
In file included from /opt/gcc-10.1.0/include/c++/10.1.0/arm-linux-gnueabihf/bits/os_defines.h:39,
                 from /opt/gcc-10.1.0/include/c++/10.1.0/arm-linux-gnueabihf/bits/c++config.h:518,
                 from /opt/gcc-10.1.0/include/c++/10.1.0/iostream:38,
                 from if_test.cpp:1:
/usr/include/features.h:424:12: fatal error: sys/cdefs.h: No such file or directory
  424 | #  include <sys/cdefs.h>
      |            ^~~~~~~~~~~~~
compilation terminated.

same error here, I tried search those header files, found them under

/usr/include/arm-linux-gnueabihf/sys/

so I copied them to include

sudo cp /usr/include/arm-linux-gnueabihf/sys/* /usr/include/sys/

done

yes, this resolved the problem for me too, thanks a lot