Dependencies and cross platform support

[ruvi-d]

Intro

This is to discuss our strategy on how we are going to manage 3rd party dependencies in nBallerina. We can use the currently required LLVM Core libs as an example and use it to set precedence.

The problem

C++ doesn't have a widely accepted dependency management system [1]

Possible solutions

The two main options to manage our dependencies are:

1. Include sources of the dependencies
   • Generally it's kept out of tree using some mechanism like git submodules
   • Rust[2], Swift[3] does this with their forks of LLVM
   • At the moment we are not doing any changes to the LLVM source code to be forced to use this option
   • Chromium project prefers to embedded the source code of it's dependencies[4]
2. Use platform specific tools to install the dependencies
   • e.g. using package manager or download and running installers
   • Something like CMake can be used to verify that the dependencies are met at compile time
   • Remove LLVM source code #52 uses this approach targeting Ubuntu, but there is a lot of work involved when we try to support other operating systems
   • There is a greater potential for version issues and dependency conflicts; especially if there are a lot of linked dependencies
   • Clean build times (also CI jobs) will be significantly faster with this approach since we don't have to build everything

Are there any other options or considerations? and what approach should we pick?

[1] : https://www.reddit.com/r/cpp/comments/58uv0a/how_do_you_manage_dependencies_in_a_crossplatform/
[2] : https://github.com/rust-lang/llvm-project
[3] : https://github.com/apple/llvm-project
[4] : https://chromium.googlesource.com/chromium/src.git/+/master/third_party/

[ruvi-d]

My +1 is for including the LLVM source as a git submodule

[ruvi-d]

Conclusion from the meeting held on 02/02/2021

Creating a “3rdparty” directory and keep source codes of the 3rd party dependencies there as soft reference (git reference). Normal builds should use released binaries of 3rd party dependencies (including LLVM), but the debug build can build source code of 3rd party dependencies (if we want to debug those dependencies). We can build these dependencies for windows or other platforms that don't have a “release” version of binaries.