This way we can commit the same amount of stack size (64 MB) without a conditional.
Includes nix, libnixexpr-tests, libnixfetchers-tests, libnixstore-tests, libnixutil-tests.
https://github.com/NixOS/nix/pull/10555 added a check requiring
that output parameters always have an uninitialized Value as argument.
Unfortunately the output parameter of the primop callback received
a thunk instead.
See the comment for implementation considerations.
builtins.strictDerivation returns an attribute set with drvPath and
output paths. For some reason, current implementation forbids drv
instead of drvPath.
After the removal of the InputAccessor::fetchToStore() method, the
only remaining functionality in InputAccessor was `fingerprint` and
`getLastModified()`, and there is no reason to keep those in a
separate class.
Add a method to check if a value has been initialized. This helps avoid
segfaults when calling `type()`.
Useful in the context of the new C API.
Closes#10524
It's a little weird we don't check the return status for these, but
changing that would introduce risk so I did not.
Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com>
Thunks are now overwritten by a helper function
`Value::finishValue(newType, payload)` (where `payload` is the
original anonymous union inside `Value`). This helps to ensure we
never update a value elsewhere, since that would be incompatible with
parallel evaluation (i.e. after a value has transitioned from being a
thunk to being a non-thunk, it should be immutable).
There were two places where this happened: `Value::mkString()` and
`ExprAttrs::eval()`.
This PR also adds a bunch of accessor functions for value contents,
like `Value::integer()` to access the integer field in the union.
Previously, `state.mkList()` would set the type of the value to tList
and allocate the list vector, but it would not initialize the values
in the list. This has two problems:
* If an exception occurs, the list is left in an undefined state.
* More importantly, for multithreaded evaluation, if a value
transitions from thunk to non-thunk, it should be final (i.e. other
threads should be able to access the value safely).
To address this, there now is a `ListBuilder` class (analogous to
`BindingsBuilder`) to build the list vector prior to the call to
`Value::mkList()`. Typical usage:
auto list = state.buildList(size);
for (auto & v : list)
v = ... set value ...;
vRes.mkList(list);
