Dear Guix community, I would like to bring once again [1] the discussion regarding the addition of a modern Ada compiler to Guix. In this case, GCC-Ada, aka GNAT.
TL;DR: GCC-Ada/GNAT cannot be bootstrapped. I would like to package a binary up until a bootstrap path is available; which is already under discussion. As far as I know, GCC-Ada has not been added to Guix for two major reasons. The first one is the lack of bootstrappability and the second one is that no one has given it a thorough try. This emails hopes to shed some light on both of these topics. 1. Bootstrapping Ada GCC-Ada (originally known as GNAT) has always required a previous GNAT version to compile newer releases. Ada was made an official language of the GCC stack with the GCC 3.1 release. Before this release, GNAT was distributed as a set of patches that had to be applied to GCC's src and it required a previous GNAT compiler to be available. I could not find "the original binary", but I have found ancient GNAT patch sets. The first (non-public) binaries were created using an Ada 83 compiler, potentially with Ada-Ed, an Ada 83 interpreter written in C (already available in Guix). However, the first publicly available patches dating from (GCC 2) already used Ada 95 features and required the Ada 95 compiler based on GCC. What does this wall of text mean? There was never a publicly available GNAT/GCC-Ada compiler that could be bootstrapped. The bootstrapping path was never made available and has been lost to history. Why did I tell all of this? Because I would like to add GCC-Ada to Guix and I am fully aware of the work that the Guix and the #bootstrappable people are doing towards a fully transparent compilation history. Opaque binaries are not allowed for that purpose. Sadly that is not currently possible with Ada. Therefore, I would like to get permission to add GCC-Ada as a binary up until there is a bootstrapping path available. I am aware that some languages/tools have received this treatment before. 2. A path towards bootstrapping GCC-Ada As I said, some of us are aware of the issue mentioned above. We have already talked about a solution. I will not explain it here. Please, read the forum posts available in [2]. However, a bootstrapping compiler is years into the future. 3. What can Ada provide to Guix? Apart from being an official language of the GCC toolsuite, it is also used in some important and unique places. For example, the graphics stack of Coreboot/Libreboot among other drivers are written in Ada [3] (you can find more by running `find . -type f -name "*.ad*"` on Coreboot's root folder). It is also the base programming language of SPARK [4], a verifiable, GPLv3 licensed, programming language, used for the ARIANE rockets and the Rosetta space probe for example. And of course, there are plenty of libraries, tools and programs written in Ada! Without a compiler, none of this can be packaged in Guix... 4. The dreaded binaries As I said, I would like to package GCC-Ada, but it would initially be a binary blob (a semi-trusted one, maybe one from the Alire [5,6] project or Debian [7]). Are the Guix maintainers okay with this? Would you accept such a commit? 4.5 Some technical data about the proposed binaries The Debian binary is just the GNAT/GCC-Ada compiler, meaning it has as dependencies gcc-12, libc6, libgmp10, libgnat-12 (Ada STL), etc. The compressed size of the package is ~18 MB, uncompressed it weighs ~91 MB. This indicates that it is not a high entropy package. However, as I said before, this is a very barebones Ada installation and it may make the package creation quite complex as other binaries may be required. The Alire installation [6] weighs 296 MB compressed. Uncompressed it becomes a 837 MB folder. The reason for the much larger weight (but still relatively low entropy) is that the Alire binary comes with the entire compilation suit. It has a C/C++ compiler, Ada, binutils, GDB, some runtime environments, etc. It is a full, self-contained installation that is designed to be a drop-in deployment to get started compiling Ada. The compilation of this package is done using this python script [8], so the process is transparent. 5. Closing up I personally would like the Alire installation media to be allowed as a binary if this proposal is accepted. This is because it is much easier to package (as the package would not need to link to other compilers or libraries) and it is the standard tooling used in the Alire project (think of Rust's Cargo but for Ada), which makes it fairly standard within the community. What do you think? Is this a good idea? Should Guix accept this? Should Guix not provide an Ada compiler unless it can be bootstrapped, which will take years? Of course, I would like to see this accepted, but I believe an initial discussion is required. [1] https://lists.gnu.org/archive/html/guix-devel/2017-01/msg01568.html [2] https://fossil.irvise.xyz/gnat-bootstrap/forum [3] https://review.coreboot.org/plugins/gitiles/coreboot/+/refs/heads/master/src/drivers/intel/gma/ [4] https://github.com/AdaCore/spark2014 [5] https://alire.ada.dev/ [6] https://github.com/alire-project/GNAT-FSF-builds/releases/tag/gnat-12.2.0-1 [7] https://packages.debian.org/bookworm/gnat-12 [8] https://github.com/alire-project/GNAT-FSF-builds Best regards and thank you for your time, Fer
