"File name too long" error when compiling files with long names

[rcoh]

could not write output to /home/russell/code/rust/rust/build/x86_64-unknown-linux-gnu/test/ui/nll/closure-requirements/region-lbr1-does-outlive-lbr2-because-implied-bound.region_lbr1_does_outlive_lbr2_because_implied_bound0-317d481089b8c8fe83113de504472633.rs.rcgu.o: File name too long

Can the test runner avoid trying to write file with names this long? I've moved my rust installation to a higher level directory to work around it.

[rcoh]

This occurs for me because my home directory is mounted on ecryptfs which only supports file names up to 143 characters

[steveklabnik]

Triage: not aware of any specific fixes here

[jyn514]

There are two ways we could make the file name shorter:

1. Write test files to /tmp instead of build/$TARGET/test. This shouldn't be too hard to implement, but not sure why build/ was chosen in the first place so hard to know what the tradeoffs are.
2. Abbreviate the test name if it goes over an arbitrary limit. We shouldn't change the source name (in src/test) but we can pass a custom --crate-name that should lead to shorter CGU filenames.

[tardyp]

FWIW, I do reproduce this issue on "normal" file system, which usually have a limit of 255 chars.

We do automatically generate crates from a interface database. This generates very long crate names, that are around 100 bytes.
When compiling using lto=thin, we do observe similar error as OP.

Workaround is to disable lto, but this is a bit annoying, so we would prefer to have this issue fixed. Hence my proposal for a patch.