printAmbiguous (used by nix-instantiate --eval and nix-env) had a depth
parameter, but all callers passed INT_MAX, effectively disabling the
limit. The function relied on the C++ stack to eventually overflow,
which could cause uncontrolled SIGSEGV crashes on deeply nested
pre-forced structures.
Now printAmbiguous checks depth against max-call-depth (default 10000)
and throws StackOverflowError with a proper trace, consistent with
other recursive value traversal functions.
The function signature is updated to take EvalState& to access the
settings and throw proper errors. The depth parameter now counts up
from 0 instead of down from INT_MAX.
nix-instantiate on deeply nested structures with recurseForDerivations
(e.g., `let x = { recurseForDerivations = true; more = x; }; in x`)
caused an uncontrolled OS-level stack overflow with no Nix stack trace.
Fix by adding call depth tracking to getDerivations, integrating with
Nix's existing max-call-depth mechanism. Now produces a controlled
"stack overflow; max-call-depth exceeded" error with a proper stack
trace.
E.g. in a derivation attribute `foo = ./bar`, if ./bar is a symlink,
we should copy the symlink to the store, not its target. This restores
the behaviour of Nix <= 2.19.
I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests
- Concepts is harder to understand, the documentation makes a good
unit vs functional vs integration distinction, but when the
integration tests are just two subdirs within `tests/` this is not
clear.
- Source filtering in the `flake.nix` is more complex. We need to
filter out some of the dirs from `tests/`, rather than simply pick
the dirs we want and take all of them. This is a good sign the
structure of what we are trying to do is not matching the structure
of the files.
With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests
functional/
installer/
nixos/
```
