dlang-packaging-issues.md

D Distribution Issue List

This is a list of issues found while making the D ecosystem available on Linux distributions such as Debian and Fedora. It is a smaller, but priorized list of the general list of issues I find while working with D that can be viewed at dlang-quirks.md.

This list is ordered by priority, more pressing issues being at the top.

LDC, DMD, DUB, DLang

1. D has no stable ABI. This kind of enforces recompiling all D shared libraries and binaries in a Linux distribution with every new compiler version. This is possible, but a major pain which requires quite some amount of manpower (Debian does this for OCaml and Haskell) - getting people to use D if it is that much extra work is harder. It also means that you can not use the libraries which were compiled with LDC in an application that is compiled with GDC and vice versa. This is a real PITA for distros and users who might have binaries compiled with the "wrong" compiler. It reduces the usefulness of development D packages in distributions a lot, if you need to recompile everything again anyway. Static linking is also frowned upon by distributions, because it triggers rebuild cascades on every bugfix that we introduce, making devlivering security updates much harder and error-prone (embedded code copies are very difficult to handle). A stable D ABI, or at least a guarantee that the ABI will not change unless there is a good reason (and the ABI change will be announced in the release notes) would help a lot. Having a D ABI that is shared between DMD, LDC and GDC would be even better.

2. Dub doesn't use packages installed to system locations (dlang/dub#838) - this renders dub pretty much unusable for using it as part of the Linux distribution package tooling. Dub also writes into $HOME as part of the build process which is considered bad practice and is disallowed on build daemons at Debian (you need to add a hack for tools which expect $HOME to be available)

3. Dub: Can not version dependencies on other libraries (dlang/dub#906) - this makes it hard to determine compatibility if we package software written in D.

4. dub test overrides the binary created by dub build (prevents automatically running tests as part of the build process) (dlang/dub#840)

5. No working Make/Ninja compatible depfile generation in LDC, DMD or GDC - this is especially important when not using dub (see the dub issues) and some other build system (Automake/CMake/Meson/..) is used instead. See ldc-developers/ldc#1802 for the LDC bug report.

6. There is no dub install command (dlang/dub#839)

7. LDC doesn't support a lot of architectures / architecture support breaks from time to time. It would be quite nice to have D tools available on as many architectures as possible. (see ldc-developers/ldc#1636 for a bug report, build logs are here: https://buildd.debian.org/status/package.php?p=ldc)

GDC Packaging Issues

The GDC issues have been separated out to not clutter the priorized overview.

1. GDC is not part of official GCC. This makes it difficult (or actually sometimes impossible) to ship it with some Linux distributions, e.g. RHEL and Fedora. On Debian, we inject GDC into the GCC build, which is also a bit weird. Having GDC in GCC proper would also give D much higher visibility.

2. GDC only supports an ancient version of the D standard library, which has many nice classes and also bugfixes missing. Because of that, it is almost impossible to compile modern D applications with GDC, and when developing a new application, support for GDC needs to be added explicitly and handled with a lot of care. This is an issue LDC doesn't have, and which is fragmenting the D ecosystem.

3. GDC does not support creating shared libraries at time, which is a big deal for distros which need it to reduce duplicate code and make security fixes easier.

Changes

• DMD is completely free software now, there is no obstacle to ship it in distributions anymore.

I see, thanks! So then I think we do need something like dub install. I think this plan should work? Or I guess an alternative would be to have the registry provide download links in a format that can be easily put into Dub's system cache.

Awesome! This is the only real dealbreaker that I remember was left from back then, and it really smells a lot more like a bug than any design decision :-)

Good news on this front, turns out only two small things were missing:

1. --temp-build flag at dependent build time;
2. A tiny fix to remove the last bit of writing to the system cache.

With both, I can successfully run dub fetch as root (yes, we still need to figure out a replacement) and dub build as unprivileged user.

If you have bandwidth to continue collaborating, perhaps there is a better place to continue this discussion?