Questions[compiler](ubuntu)

I am currently using Ubuntu 18.04, and I need gcc 4.8 for MATLAB. So I tried to install gcc-4.8 using

$ sudo apt-get install gcc-4.8
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/l/linux/linux-libc-dev_4.15.0-117.118_amd64.deb  404  Not Found [IP: 2403:8940:3:1::f 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

so I ran the command

sudo apt-get update 

I didn't show any error but running gcc version command gave this

$ gcc -v
Command 'gcc' not found, but can be installed with:
sudo apt install gcc

previously I used to have 7.5 but now it is not.

I'm trying to use CLions interface to gcov but I'm not using the default g++ compiler (for Ubuntu 18.04). Therefore my version of gcov (7.5) is incompatible with my compiler (10.1).

How can I install gcov that works with gcc / g++ 10.1 ?

I've tried:

• sudo apt install gcov
• sudo apt install gcov-10
• sudo apt install gcov-dev

how do I set Clang 9 as the default C++ compiler on Ubuntu 19.10? I searched the internet, but nothing helped. Thank you for answer :)

In the new Ubuntu 18.04:

• What's the default GCC version (with which the binaries were built)?
• What GCC versions are available as separate packages (and what minor version is installed if I install GCC 4, 5, 6, 7 or 8 respectively)?
• What Clang versions are available as separate packages (and what minor version is installed if I install clang 4 or 5?)

I can't find this in any release notes (and I don't want to have to install just to check.)

Is there a need to install a C/C++ compiler in Ubuntu 14.04 LTS? Where to write the program? How to compile the same?