Shorten the path of the RPM-controlled per-build directory

[lantw44]

Is it possible to shorten the <package>-<version>-build part from a spec file?

I package Guix in Fedora Copr. To run Guix tests in the rpmbuild %check step, the full path of the working directory cannot be longer than 29 bytes. The default /builddir/build/BUILD/guix-1.4.0 used by mock is already too long, so I have to change the default test-tmp directory used by Guix tests to t to save a few bytes in order to run tests.

Now the new default /builddir/build/BUILD/guix-1.4.0-build/guix-1.4.0 is even longer than /builddir/build/BUILD/guix-1.4.0, so the test-tmp → t trick can't work. Is it possible to tell rpmbuild to use a shorter path than guix-1.4.0-build, or I should just mktemp -d and tell Guix to run tests in the temporary directory?

#2078
#2885

[pmatilai]

No there isn't. The precise location of that directory is rpm's business only.

What's this absurd 29 byte limit? I'd suggest patching that instead.

[lantw44]

Each Guix package directory includes a hash, so it is typical for a directory to take 50 bytes. For example, you can find /gnu/store/4y5m9lb8k3qkb1y9m02sw9w9a6hacd16-bash-minimal-5.1.8 in its official binary tarball. The problem is that Guix uses this kind of long path in shebangs and Unix socket paths, so it can hit the limit if the test directory is too long.

It looks like moving the test directory to /tmp (using mktemp -d) with an autoconf cache variable is the only solution.

[voxik]

The path certainly become too long:

https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/FZSQW6CMUWBUGW6YVJ4IXPSVODKPXNR6/

[lantw44]

Yes, Guix has length checks. These lines are extracted from the build log on Fedora 40:

checking for the store directory... /gnu/store
checking the length of the installed socket file name... 30
checking for unit test root directory... (cached) /builddir/build/BUILD/guix-1.4.0/t
checking the length of the socket file name used in tests... 66
checking the length of a typical hash bang line... 73
checking the length of a hash bang line used in tests... 103