Potential issue building on Windows

[chreekat]

Hello,

Recently, while building cabal-install on Windows, I ran into an issue that had to do with upgrading from 0.6.3.0 to 0.7.0.0.

The saga is here: haskell/cabal#9775

To begin, pkg-config isn't available in the Windows environment used in that CI. Since 0.7.0.0 introduced a default dependency on pkg-config, I updated the Cabal project to use constraints: zlib -pkg-config. No real harm done there.

But then, I got a strange error, possibly when linking cabal-install:

Configuring executable 'cabal' for cabal-install-3.11.0.0..
Preprocessing executable 'cabal' for cabal-install-3.11.0.0..
Building executable 'cabal' for cabal-install-3.11.0.0..
[1 of 1] Compiling Main             ( main\Main.hs, C:\\GitLabRunner\builds\0\1797238\dist-newstyle\build\x86_64-windows\ghc-9.2.3\cabal-install-3.11.0.0\x\cabal\build\cabal\cabal-tmp\Main.o )
Linking C:\\GitLabRunner\\builds\\0\\1797238\\dist-newstyle\\build\\x86_64-windows\\ghc-9.2.3\\cabal-install-3.11.0.0\\x\\cabal\\build\\cabal\\cabal.exe ...
Cleaning up project directory and file based variables
ERROR: Job failed: exit status 127

When I looked into the matter, it looks like 0.6.3.0 uses the bundled C zlib by default on Windows, and 0.7.0.0 did not. By adding constraints: zlib +bundled-c-zlib on the Windows build, I was able to get a successful CI pipeline.

Now, this could simply be an issue with the CI environment, or maybe a bug with GHC (or Cabal) when trying to use the zlib that is bundled with GHC. I'm opening this just for visibility. I won't be looking into this much more myself at the present.

[chreekat]

p.s. Rather than writing everything I just wrote, I could have just linked to this commit :)

[Bodigrim]

Now, this could simply be an issue with the CI environment

Indeed so. When extra-libraries: z is not found, Cabal fails during build of zlib itself with something like

Error: [Cabal-4345]
Missing dependency on a foreign library:
* Missing (or bad) C library: z

The fact that it proceeds until linking cabal.exe suggests that something is off with the wider environment: libz.a is present, but unlinkable for some reason. Your choice of GHC 9.2.3 is quite unorthodox, I'd suggest upgrading at least to 9.2.8.

To begin, pkg-config isn't available in the Windows environment used in that CI. Since 0.7.0.0 introduced a default dependency on pkg-config, I updated the Cabal project to use constraints: zlib -pkg-config.

This is an automatic flag. You would not have to do anything manual if you used a more modern version of bootstrap Cabal than 3.6.

---

Feel free to reopen if there is more specific evidence that it's zlib who is at fault.

[chreekat]

Thanks for the pointers. This does not surprise me. I (and others) are independently trying to modernize the release CI for cabal, but it's still WIP.