Add C++ support (GCC and Clang) on all platforms

[kcgen]

Tool information

• Tool names: defacto C++ compilers: GCC and Clang

• Add or update? Add

• Desired versions: Latest version available in standard package repositories. Currently these are:

  Compiler	Version	OS	Package Manager(s)
  GCC	9	all	apt, Brew, MacPorts, and MSYS2
  Clang	8	Ubuntu-19.04	apt
  Clang	9	macOS and Windows	Brew and Chocolatey

• Approximate size: Clang depends on GCC (that's why it often makes sense to simply install both; in addition to their technical differences). Typically the combo is a couple GB on Windows and smaller on macOS and Linux.

• Brief description of packages: These C++ compilers are used to build literally every C++ autotools/cmake project out there (tens of thousands of open-source applications and tools; perhaps more on GitHub).

  The main goal of this request is to allow the vast majority of open source C/C++ packages to be ./configure'd and built with either compiler (assuming the user pulls in any package-specific dependencies) "out of the box".

• Homepages: GCC - https://gcc.gnu.org/, Clang - https://clang.llvm.org/

Virtual environments affected

• ☑️ macOS 10.15
• ☑️Ubuntu 16.04 LTS
• ☑️ Ubuntu 18.04 LTS
• ☑️ Windows Server 2016 R2
• ☑️ Windows Server 2019

Can they be installed during the build?
Yes. I'm currently installing the following in my workflow:

Compilers	OS	Package Manager	Time
GCC and Clang	Ubuntu	apt	< 60s
GCC	macOS	Brew and MacPorts	between 3 min and 5 min
GCC and Clang	Windows	MSYS2's pacman	between 8 min and 12 min

Compiling my application takes less time than installing these.

Because of this excessive time and resource usage, I made use of GitHub's new cache feature available in CI workflows, however, the cache limit is (currently) too small to save most of these development stacks.

Because it seems absurd that GitHub's cache size cannot accommodate C++ "hello world", I flagged
it here to which GitHub staff member @chrispat suggested that I shouldn't be caching C++ dependencies and instead they should be available in the baseline VMs.

Are you willing to submit a PR?
Yes

[stevencpp]

I would prefer to have clang-9 installed. Most people should be using the latest release. We could also have both the default clang (version 8) and clang-9 installed.

[kcgen]

@stevencpp , yes, I would prefer that the latest compiler (as determined by the package manager), be installed by default. Can you let me know on which OS clang-9 is available via the package manager? Thank you; I will update my issue.

[stevencpp]

On Ubuntu I use this to install it as clang-9 (takes about a minute):

wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key 2>/dev/null | sudo apt-key add -
sudo add-apt-repository 'deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main' -y
sudo apt-get update -q
sudo apt-get install -y clang-9 lld-9 libc++-9-dev libc++abi-9-dev clang-tools-9

and on windows I use this (takes 25 seconds):

curl -fsSL -o LLVM9.exe https://releases.llvm.org/9.0.0/LLVM-9.0.0-win64.exe
7z x LLVM9.exe -y -o"C:/Program Files/LLVM"

I haven't tried setting it up on macOS yet.

[kcgen]

Interesting; even though Clang-9 is not in Ubuntu's 19.04 baseline APT repo, nor in macOS's Brew or MacPorts repos, nor in MSYS2's pacman repo -- I do see that these are official releases from LLVM.org.

I would prefer to use latest version per the repos due to the level of integration they provide (ie: pacman under msys2 will pull in dependencies and allow most autotools packages to build - where as a standalone exe installer might be totally disconnected from the msys2 environment). I realize the trade-off here is having to wait a bit longer for the lastest version to be supported by the various operating system repositories.

The main goal of this request is to allow the vast majority of open source C/C++ packages to be ./configure'd and built with either compiler (assuming the user pulls in any package-specific dependencies), as well as support the creation or modifications of similar autotools/cmake type C++ projects "out of the box".

I've amended the version line in the request with a mix of this goal combined with your suggestion; thanks @stevencpp!

[stevencpp]

Chocolatey https://chocolatey.org/packages/llvm and scoop https://github.com/ScoopInstaller/Main/blob/master/bucket/llvm.json have 9.0.0.
https://packages.msys2.org/base/mingw-w64-clang says pacman should have 9.0.0 as well, but I'd rather not use msys for clang. GCC may need msys/cygwin, but for clang I'm guessing most people use it without msys on windows (especially now that Visual Studio comes with clang-cl support built in). The official binary package includes the whole toolchain so it doesn't depend on GCC and cmake works fine with it, no need to depend on msys.
Also https://formulae.brew.sh/formula/llvm suggests brew on macOS should have 9 by default as well ?

[kcgen]

@stevencpp, you've got more experience with Clang under windows than myself; thanks for all of this! I've updated the version block.

I left out mentioning that Scoop or MSYS2 could be used to install Clang 9 because it seems like Chocolatey is the prefered approach (want to keep this to the "best" recommended installations only). Does it read OK now?

[stevencpp]

Seems alright.

There's a proposed llvm-toolchain-9 package for apt https://launchpad.net/ubuntu/+source/llvm-toolchain-9/1:9-2~ubuntu18.04.1 so that might land as well soon ?

[zbeekman]

If you're going to install the latest stable GCC it would be really nice to include GFortran along with C/C++. On some package managers (Homebrew) you get gfortran and g++ with gcc (e.g., brew install gcc) but on others (at least linux) you need to apt-get install gfortran-<version>, possibly after adding the toolchain-r/test ppa.