Install gcc from source: bash: gcc -v /usr/bin/gcc: Is a directory - c++

Question

I just installed gcc-8.1 from source using those steps:
wget https://ftp.gnu.org/gnu/gcc/gcc-8.1.0/gcc-8.1.0.tar.gz
tar xvf gcc-8.1.0.tar.gz
cd gcc-8.1.0
apt build-dep gcc
./contrib/download_prerequisites
cd ..
mkdir objdir
cd objdir
$PWD/../gcc-8.1.0/configure --prefix=/usr/bin/gcc-8.1 --enable-languages=c,c++,fortran,go --disable-multilib
make -j8
make install
Everything is correct?
Then I add it to update-alternatives
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8.1 60 --slave /usr/bin/g++ g++ /usr/bin/g++-8.1
There are 3 choices for the alternative gcc (providing /usr/bin/gcc).
Selection Path Priority Status
------------------------------------------------------------
0 /usr/bin/gcc-7 60 auto mode
1 /usr/bin/gcc-5 60 manual mode
* 2 /usr/bin/gcc-7 60 manual mode
3 /usr/bin/gcc-8.1 60 manual mode
Press <enter> to keep the current choice[*], or type selection number: 3
update-alternatives: using /usr/bin/gcc-8.1 to provide /usr/bin/gcc (gcc) in manual mode
update-alternatives: warning: skip creation of /usr/bin/g++ because associated file /usr/bin/g++-8.1 (of link group gcc) doesn't exist
My issue is when I type gcc -v, it said bash: /usr/bin/gcc: Is a directory

Answer 1

--prefix=/usr/bin/gcc-8.1 means that everything that is part of the installation will be placed in the /usr/bin/gcc-8.1/ directory.1
This means that your actual GCC binary is probably located at /usr/bin/gcc-8.1/bin/gcc (or some similarly-named executable, maybe it is actually called gcc-8 or gcc-8.1).
When you set the GCC binary to /usr/bin/gcc-8.1 using update-alternatives, you set the symlink that is normally used to resolve which GCC binary you want to a directory - resulting in the error that you are now getting.
To fix this issue, follow these steps:
Remove the wrong entry in update-alternatives:
update-alternatives --remove gcc /usr/bin/gcc-8.1
Add the right entry.2
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8.1/bin/gcc 60 \
--slave /usr/bin/g++ g++ /usr/bin/gcc-8.1/bin/g++
1 Well, mostly, anyways. Usual prefixes include / (binaries in /bin/), /usr/ (binaries in /usr/bin/) and /usr/local/ (binaries in /usr/local/bin/)
2 I am assuming you want to keep GCC installed at that awkward location. Recompiling and re-installing with --prefix=/opt/gcc-8.1 or something similar would probably be better, just modify the path as needed

Answer 2

This is a double edged sword. I am on windows so don't have the linux jargon. But located my gcc problem in a very wierd way. But maybe this will help someone from hours of digging and trying this and that. But cant say i have not learned a lot in the process.
gcc 10.4 release for windows
and that at least got me to here
Read down to the soundforge link