add llvm repo to ubuntu / linux mint and symlink llvm binaries, making it the default compiler

add-llvm.pl

#!/usr/bin/perl -w

use strict;

# update this whe n new versions of llvm come out
my $llvm_version = 19;

# mint has a file that lets you know the ubuntu upstream release version
sub get_dist_version_from_mint {
    open my $fh, '<', '/etc/upstream-release/lsb-release' or die;

    my $codename = '';
    while (my $line = <$fh>) {
        if ($line =~ /^DISTRIB_CODENAME=(\S+)/) {
            $codename = $1;
        }
    }

    close $fh;

    return $codename;
}

sub read_os_release {
    my $os_release_file = '/etc/os-release';
    my %os_info;

    if (-e $os_release_file) {
        open my $fh, '<', $os_release_file or die "Could not open '$os_release_file': $!";
        while (my $line = <$fh>) {
            chomp $line;  # Remove newline character
            if ($line =~ /^(.*)=(.*)$/) {
                my $key = $1;
                my $value = $2;
                # Remove surrounding quotes from the value
                $value =~ s/^"(.*)"$/$1/;
                $value =~ s/^'(.*)'$/$1/;
                $os_info{$key} = $value;
            }
        }
        close $fh;
    }

    return %os_info;
}



sub run_cmd {
    my $cmd = shift;

    print("> $cmd\n");
    return system($cmd) == 0;
}

sub apt_source {
    my $llvm_version = shift;
    my $dist_version = shift;
    
    return "deb http://apt.llvm.org/$dist_version/ llvm-toolchain-$dist_version-$llvm_version main";
}


# debian alternative priority
my $priority = 100;

my %os_release = read_os_release();
my $dist_version = $os_release{UBUNTU_CODENAME};

die $dist_version;

run_cmd("wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -");

# attempt removal of old apt source, may silently fail
my $old_apt_source = apt_source($llvm_version - 1, $dist_version);
run_cmd("add-apt-repository --remove \"$old_apt_source\"");

my $new_apt_source = apt_source($llvm_version, $dist_version);
run_cmd("add-apt-repository \"$new_apt_source\"");

run_cmd("apt update");

my @packages = qw(clang lldb lld llvm clang-format clang-tidy clang-tools);
my $cmd = "apt -y install ";
foreach (@packages) {
    my $pkg_name = $_ . "-" .$llvm_version;
    $cmd .= "$pkg_name ";
}

run_cmd($cmd);

my @programs =  qw(clang clang++ clang-tidy clang-format scan-build lldb lld llvm-config);

# remove existing alternatives
foreach (@programs) {
    run_cmd("update-alternatives --remove-all $_");
}

# now install alternatives
foreach (@programs) {
    my $pkg_name = $_ . "-" .$llvm_version;
    run_cmd("update-alternatives --install /usr/bin/$_ $_ /usr/bin/$pkg_name $priority");
}