This is caused, through several layers of absurdity, by runtime type
information of Nix things being invisible due to -fvisibility=hidden
inside n-e-j.
We don't have any idea why n-e-j has -fvisibility=hidden, since blame
says it's from the initial commit. It is plausible that it was some
ill-advised optimization but it's not sound.
The crash is caused by dynamic_cast<RootArgs *>(MyArgs *) failing, which
is in turn caused by the RTTI being invisible.
See: https://www.qt.io/blog/quality-assurance/one-way-dynamic_cast-across-library-boundaries-can-fail-and-how-to-fix-it
Fixes: #2
EvalState::error does not return an exception instance in lix, but an
exception *builder*. throwing this thing will not trigger any catches,
which then causes the worker process to die without reporting an error
to the collector. this confuses the collector and causes *it* to exit,
effectively breaking nix-eval-jobs for anything that has broken attrs.
While the previous style seems more sensible to me (the header names
are quite generic), the pkg-config definitions both from upstream Nix
and from Lix specify -I${includedir}/nix in CFLAGS rather than
-I${includedir}. This may be worth changing, but for now I want
nix-eval-jobs to work and this does what I want.
writeLine will throw a SysError exception, which obfuscates out-of-memory events where the eval worker is killed by the OS.
readLine is suffering from the same problem and will be handled in a subsequent commit.
Currently, not a lot of things expose inputDrvs (except
`show-derivation`), which is a showstopper whenever you want to compute
popularity ranking based on the dependency relation.
Having `inputsDrvs` in the reply enable downstream users to perform such
computations in an efficient way.
