Install GCC 4.9.3

install-gcc-4.9.3.sh

#!/bin/bash

# this script installs GCC 4.9.3 
# to use it navigate to your home directory and type:
# sh install-gcc-4.9.3.sh

# download and install gcc 4.9.3
wget https://ftp.gnu.org/gnu/gcc/gcc-4.9.3/gcc-4.9.3.tar.gz
tar xzf gcc-4.9.3.tar.gz
cd gcc-4.9.3
./contrib/download_prerequisites
cd ..
mkdir objdir

cd objdir
../gcc-4.9.3/configure --prefix=$HOME/gcc-4.9.3 --enable-languages=c,c++,fortran,go --disable-multilib
make

# install
make install

# clean up
rm -rf ~/objdir
rm -f ~/gcc-4.9.3.tar.gz

# add to path (you may want to add these lines to $HOME/.bash_profile)
export PATH=$HOME/gcc-4.9.3/bin:$PATH
export LD_LIBRARY_PATH=$HOME/gcc-4.9.3/lib:$HOME/gcc-4.9.3/lib64:$LD_LIBRARY_PATH

work with two patches (with gcc 9.4.0, ubuntu 20.04):

1. https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=ec1cc0263f156f70693a62cf17b254a0029f4852#patch2
2. https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=883312dc79806f513275b72502231c751c14ff72

... and if you have some problems with sanitizer lib, you can make with --disable-libsanitizer , but it should be a patch for this (it is here: https://reviews.llvm.org/D47281 , but does not work with my configuration).