Chapel 1.25 update notes

Notes on updating to Chapel 1.25

Hi Isaac —

In Chapel 1.25, we have switched our default compiler back-end to being LLVM-based rather than C-based as in past releases. I remember you venting about LLVM build times in our early interactions, so wanted to post this note to make sure the change doesn't catch you off-guard if/when you upgrade.

First, you can opt to stick with the C-based back-end for simplicity by setting CHPL_LLVM=none before building Chapel.

However, if you have LLVM 11 installed (with accompanying developer packages), the Chapel build ought to detect it, infer CHPL_LLVM=system (or you can set it manually), and make use of it. The complete suggested set of packages for Ubuntu is:

$ sudo apt-get install gcc g++ m4 perl python3 python3-pip python3-venv python3-dev bash make mawk git pkg-config cmake llvm-11-dev llvm-11 llvm-11-tools clang-11 libclang-11-dev libclang-cpp11-dev libedit-dev

[command edited to reflect guidance for December's Chapel 1.25.1]

The option of last resort is to build LLVM from sources that we bundle into our release, by setting CHPL_LLVM=bundled before building, but that gets back to the expensive build times concern, so I'm not suggesting it.

the application conftest has stopped unexpectedly should be fixed

Thanks for reporting this third-party configuration error last time around. We passed it back to the original development team, whose fix we pulled into this release, so hopefully you should not run into it again.

Thanks for continuing to maintain the site,

-Brad