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This is part of a fix for b/338.
We should never use PartialOrd::partial_cmp().
All Nix types except floats are obviously totally-ordered. In
addition, it turns out that because Nix treats division by zero
rather than producing a NaN, and because it does not support
"negative zero", even floats are in fact totally ordered in Nix.
Therefore, every call to PartialOrd::partial_cmp() in tvix is an
error. We have to *implement* this function, but we should never
call it on built-in types.
Moreover, nix_cmp_ordering() currently returns an Option<Ordering>.
I'm not sure what was going on there, since it's impossible for it
to return None. This commit fixes it to return simply Ordering
rather than Option<Ordering>.
Change-Id: If5c084164cf19cfb38c5a15554c0422faa5f895d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10218
Autosubmit: Adam Joseph <adam@westernsemico.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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This commit rewrites Value::nix_eq() into an equivalent. Except for
calls to Thunk::force(), the new form no longer uses generators, and
is async only because of the fact that it calls Thunk::force().
I believed that the nonrecursive form would be faster. It is, in
fact, slightly slower. I believe this is due to the vec![]
allocation; I am investigating.
Prev-Nixpkgs-Benchmark: {"attrpath":"pkgsCross.aarch64-multiplatform.hello.outPath","peak-kbytes":"459068","system-seconds":"0.71","user-seconds":"5.39"}
This-Nixpkgs-Benchmark: {"attrpath":"pkgsCross.aarch64-multiplatform.hello.outPath","peak-kbytes":"460048","system-seconds":"0.68","user-seconds":"5.73"}
Change-Id: I10f4868891e4b7475df13f0cbc41ec78dd985dd8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10118
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: Adam Joseph <adam@westernsemico.com>
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Change-Id: Ic2bd4e8291b30ceac9fa0e88a4f56e61ae99b603
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10227
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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Change-Id: I4bd85dbe9c27047f4abbdeff4e2b796e9bcab3a1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10211
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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This commit rewrites Thunk::force() so that it is not (directly)
self-recursive. It maintains a Vec of all the
previously-encountered thunks which point to the one it is currently
forcing, rather than recursively calling itself.
Benefits:
- Short term:
This commit saves the cost of a round-trip through the generator
machinery for the generators::request_force() which is removed by
this commit.
- Medium term:
Once a similar transformation has been applied to nix_cmp(),
nix_add(), nix_eq(), and coerce_to_string(), those four functions,
along with Thunk::force(), will make non-tail calls only to each
other. They can then be merged into a single tail-recursive
function which does not use the generator machinery at all:
enum Task { Cmp, Add, Eq, CoerceToString, Force};
fn Value::walk(task:Task, v1:Value, v2:Value) {
// ...
- Long term:
The long-term goal here is to use generators **only for builtins**
and [Marionette]-style remote control of the VM. In other words:
use `async` for things that actually involve concurrency. Calls
from the VM to builtins can then be blocking calls, because even
cppnix will overflow the stack if you make a MAX_STACK_DEPTH-deep
recursive call which passes through a builtin at every stack frame
(e.g. `{ func = builtins.sort (a: b: ... func ...) ...}`).
This way the inner "tight loop" of the interpreter doesn't pay the
costs of `async` and generators. These costs manifest in terms
of: performance, complex nonlocal control flow, and language
impediments (async Rust is a restricted subset of real Rust, and
is missing things like traits).
[Marionette]: https://firefox-source-docs.mozilla.org/testing/marionette/Intro.html
Change-Id: I6179b8abb2ea0492180fcb347f37595a14665777
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10039
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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If builtins.substring is invoked with (byte!!) offsets that aren't at
codepoint boundaries, return an error rather than panicking. This is
still incorrect (see b/337) but pushes the incorrectness forward a step.
Change-Id: I5a4261f2ff250874cd36489ef598dcf886669d04
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10199
Tested-by: BuildkiteCI
Autosubmit: grfn <grfn@gws.fyi>
Reviewed-by: sterni <sternenseemann@systemli.org>
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This fixes a *future* clippy lint:
https://rust-lang.github.io/rust-clippy/master/index.html#/incorrect_partial_ord_impl_on_ord_type
In essence, because the implementation of *both* Ord and PartialOrd
implies that ordering is not partial, all results of PartialOrd should
simply be those of Ord. This is to avoid subtle bugs in future
refactorings.
Change-Id: I8fc6694010208752dd47746a2aaaeca0c788d574
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10109
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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Change-Id: I4eab5c81fb82337da06327248845cd2f3a4490d3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10038
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: Adam Joseph <adam@westernsemico.com>
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This commit adds Thunk::unwrap_or_clone(), which uses
Rc::try_unwrap() to avoid cloning the Value out of a an Rc which has
only one strong reference.
Change-Id: Icacefe0c823dcddf046d90c0c5cd5ed59fe976d4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10037
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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For cases where clippy lints don't apply to us, or something is
misfiring, add appropriate configuration.
Relates to b/321.
Change-Id: I0af453910b4a4112bf685b2a8e9a73de10ec87ea
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9965
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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Uses the standard library IntoIterator trait for the construction of
our iterators. Clippy complains about duplicating this.
While doing this, I opted to rename the `IntoIter` type into something
that is more useful to users, in case somebody ends up working with
these manually.
This fixes a clippy lint, and is related to b/321.
Change-Id: I851fde0d7b8b38d182343a0fd6d9f8dd2a33ee11
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9963
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
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Relates to b/321.
Change-Id: I37284f89b186e469eb432e2bbedb37aa125a6ad4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9961
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
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Delays allocation (through cloning) of the values to be compared
until *after* the keys have been compared.
Change-Id: I7d68c27d7a0fbcdcc387db7c092bce50ca4b94ea
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9900
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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Similar to `into_iter_sorted`, add a marker function for call sites
that want *borrowed* sorted iteration.
Change-Id: I7c6f14e1ac43fdb14b861b3da183eb5d12bba139
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9899
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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This commit makes catchable errors a variant of Value.
The main downside of this approach is that we lose the ability to
use Rust's `?` syntax for propagating catchable errors.
Change-Id: Ibe89438d8a70dcec29e016df692b5bf88a5cad13
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9289
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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There's some more left, but they've been renamed/refactored out of
sight.
Change-Id: I41579dedc74342b4c5f8cb39d2995b5b0c90b0f4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9372
Tested-by: BuildkiteCI
Reviewed-by: Connor Brewster <cbrewster@hey.com>
Autosubmit: flokli <flokli@flokli.de>
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In cppnix 2.17, commit b72bc4a972fe568744d98b89d63adcd504cb586c, the
libexpr pretty-printing routine was fixed so that it would no longer
pretty-print attrsets with keywords in their attrnames incorrectly.
This commit implements the corresponding fix for tvix, fixes our
tests to work with cppnix>=2.17 oracles, and expands our test cases
to cover all the keywords.
Change-Id: I4b51389cd3a9c44babc8ab2a84b383b7b0b116ca
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9283
Autosubmit: Adam Joseph <adam@westernsemico.com>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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Change-Id: I0b2fdb418c2e36280d5c551a81634e1742193903
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9105
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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Change-Id: I6b1b902ccbc12bf2acdb0fdf406d6ef336ff0b2f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9098
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
Autosubmit: flokli <flokli@flokli.de>
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Change-Id: Iaeb9ed7024c2ce85373f8aec0d223f52e1a3a539
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9097
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Change-Id: Ic58653254b36694f1991a18db9ceea0d532c2e31
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9068
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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This fixes a subtle issue which would occasionally lead to a crash (e.g.
when evaluating (pkgs.systemd.outPath with --trace-runtime): With each
character in the string that has a multi byte representation in UTF-8,
the actual byte position and what tvix thought it was would get out of
sync. This could either lead to
* Tvix swallowing characters or jumbling characters if multi byte
characters would cause the tracked index to become out of sync with
the byte position before the first character to be escaped, or
* Tvix crashing if (in the same situation) the out of sync index would
be within a UTF-8 byte sequence.
Luckily, std's `char_indices()` iterator implements exactly what
`nix_escape_char()`'s original author had in mind with
`.chars().enumerate()`. Using `i + 1` for continuing is safe, since all
characters that need (in fact, can) to be escaped in Nix are represented
as a single byte in UTF-8.
Change-Id: I1c836f70cde3d72db1c644e9112852f0d824715e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8952
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
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When dealing with a formal argument in a function argument pattern that
has a default expression, there are two different things that can happen
at runtime: Either we select its value from the passed attribute
successfully or we need to use the default expression. Both of these may
be thunks and both of these may need finalisers. However, in the former
case this is taken care of elsewhere, the value will always be finalised
already if necessary. In the latter case we may need to finalise the
thunk resulting from the default expression. However, the thunk
corresponding to the expression may never end up in the local's stack
slot. Since finalisation goes by stack slot (and not constants), we need
to prevent a case where we don't fall back to the default expression,
but finalise anyways.
Previously, we worked around this by making `OpFinalise` ignore
non-thunks. Since finalisation of already evaluated thunks still
crashed, the faulty compilation of function pattern arguments could
still cause a crash.
As a new approach, we reinstate the old behavior of `OpFinalise` to
crash whenever encountering something that is either not a thunk or
doesn't need finalisation. This can also help catching (similar)
miscompilations in the future. To then prevent the crash, we need to
track whether we have fallen back or not at runtime. This is done using
an additional phantom on the stack that holds a new `FinaliseRequest`
value. When it comes to finalisation we check this value and
conditionally execute `OpFinalise` based on its value.
Resolves b/261 and b/265 (partially).
Change-Id: Ic04fb80ec671a2ba11fa645090769c335fb7f58b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8705
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
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In order for the test suite we have currently to be comparable to C++
Nix, we need to display values in the same way. This was largely the
case except in some weird cases.
* <CODE> for thunks and <CYCLE> for repeated thunks (?) are already in
use. <CODE> formatting is tested by the oracle test suite already.
* Instead of lambda, we need to use <LAMBDA>
* <<primop>> and <<primop-app>> (a formatting C++ Nix uses nowhere)
now are <PRIMOP> and <PRIMOP-APP>.
We'll probably want to have a fancier display of values (in a separate
trait) down the line. This could be used for interactive usage, e.g. the
REPL or a potential debugger.
There is a peculiarity with C++ Nix 2.3 formatting primops: import is
considered a <<PRIMOP-APP>>, since it is internally implemented by means
of scopedImport. This implementation detail no longer leaks in C++ Nix
2.13 nor in Tvix.
<CYCLE> display is untested at the moment, since we exhibit a
discrepancy to C++ Nix 2.3. Our current detection is more similar to C++
Nix 2.13—luckily it is also the more consistent of the two. See also
b/245.
Change-Id: I1d534434b02e470bf5475b3758920ea81e3420dc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8760
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
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C++ Nix forces and typechecks the passed argument even if it is not
necessary in order to compute the return value of the function. I
discovered this when I thought our formals miscompilation might be that
we are too strict, but doesn't look like it in this case.
Change-Id: Ifb3c92592293052c489d1e3ae8c7c54e4b6b4dc6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8701
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
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mapAttrs, map and genList call Nix functions provided by the caller and
store the result of applying them in a Nix data structure that does not
force all of its contents when forced itself. This means that when such
a builtin application is forced, the Nix function calls performed by the
builtin should not be forced: They may be forced later, but it is also
possible that they will never be forced, e.g. in
builtins.length (builtins.map (builtins.add 2) [ 1 2 3 ])
it is not necessary to compute a single application of builtins.add.
Since request_call_with immediately performs the function call
requested, Tvix would compute function applications unnecessarily before
this change. Because this was not followed by a request_force, the
impact of this was relatively low in Nix code (most functions return a
new thunk after being applied), but it was enough to cause a lot of
bogus builtins.trace applications when evaluating anything from
`lib.modules`. The newly added test includes many cases where Tvix
previously incorrectly applied a builtin, breaking a working expression.
To fix this we add a new helper to construct a Thunk performing a
function application at runtime from a function and argument given as
`Value`s. This mimics the compiler's compile_apply(), but does itself
not require a compiler, since the necessary Lambda can be constructed
independently.
I also looked into other builtins that call a Nix function to verify
that they don't exhibit such a problem:
- Many builtins immediately use the resulting value in a way that makes
it necessary to compute all the function calls they do as soon as
the outer builtin application is forced:
* all
* any
* filter
* groupBy
* partition
- concatMap needs to (shallowly) force the returned list for
concatenation.
- foldl' is strict in the application of `op` (I added a comment that
makes this explicit).
- genericClosure needs to (shallowly) force the resulting list and some
keys of the attribute sets inside.
Resolves b/272.
Change-Id: I1fa53f744bcffc035da84c1f97ed25d146830446
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8651
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
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Change-Id: Ie4c563e933f571f45cb4f4efe650d1b65f119e8d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8324
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Autosubmit: tazjin <tazjin@tvl.su>
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This reports the span
1. of the code within a thunk,
2. of the place where the thunk was instantiated,
3. of the place where the thunk was first forced,
4. of the place where the thunk was forced again,
when yielding an infinite recursion error, which hopefully makes it
easier to debug them.
The spans are tracked in the ThunkRepr::Blackhole variant when putting
a thunk under evaluation.
Note that we currently have some loss of span precision in the VM loop
when switching between frame types, so spans 3/4 are currently a bit
wonky. Working on it.
Change-Id: Icbd2a9df903d00e8c2545b3fc46dcd2a9e3e3e55
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8270
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
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This is step 1 towards being able to use all 4 spans that we know when
dealing with infinite recursion. It tracks the span at which the
force of a thunk was first requested when constructing a blackhole, so
that we can highlight the spans of the first and second forces.
These are actually the least relevant spans, but the easiest to put in
place, more coming soon.
Change-Id: I4c7e82f6211b98756439d4148a4191457cc46807
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8269
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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Given Rust's current lack of support for tail calls, we cannot avoid
using `async` for builtins. This is the only way to avoid
overflowing the cpu stack when we have arbitrarily deep
builtin/interpreted/builtin/interpreted/... "sandwiches"
There are only five `async fn` functions which are not builtins
(some come in multiple "flavors"):
- add_values
- resolve_with
- force, final_deep_force
- nix_eq, nix_cmp_eq
- coerce_to_string
These can be written iteratively rather than recursively (and in
fact nix_eq used to be written that way!). I volunteer to rewrite
them. If written iteratively they would no longer need to be
`async`.
There are two motivations for limiting our reliance on `async` to
only the situation (builtins) where we have no other choice:
1. Performance.
We don't really have any good measurement of the performance hit
that the Box<dyn Future>s impose on us. Right now all of our
large (nixpkgs-eval) tests are swamped by the cost of other
things (e.g. fork()ing `nix-store`) so we can't really measure
it. Builtins tend to be expensive operations anyways
(regexp-matching, sorting, etc) that are likely to already cost
more than the `async` overhead.
2. Preserving the ability to switch to `musttail` calls.
Clang/LLVM recently got `musttail` (mandatory-elimination tail
calls). Rust has refused to add this mainly because WASM doesn't
support, but WASM `tail_call` has been implemented and was
recently moved to phase 4 (standardization). It is very likely
that Rust will get tail calls sometime in the next year; if it
does, we won't need async anymore. In the meantime, I'd like to
avoid adding any further reliance on `async` in places where it
wouldn't be straightforward to replace it with a tail call.
https://reviews.llvm.org/D99517
https://github.com/WebAssembly/proposals/pull/157
https: //github.com/rust-lang/rfcs/issues/2691#issuecomment-1462152908
Change-Id: Id15945d5a92bf52c16d93456e3437f91d93bdc57
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8290
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: Adam Joseph <adam@westernsemico.com>
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This rewrites nix_cmp_ordering as an iterative loop, which
eliminates the extra pinned-boxing helper function.
Change-Id: I33d0ecc913e02affd8fd4c7bc1c9ecfdf4c7deb9
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8288
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Autosubmit: Adam Joseph <adam@westernsemico.com>
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This drops the usage of serde::Serialize, as the trait can not be used
to implement the correct semantics (function colouring!).
Instead, a manual JSON serialisation function is written which
correctly handles toString, outPath and other similar weirdnesses.
Unexpectedly, the eval-okay-tojson test from the C++ Nix test suite
now passes, too.
This fixes an issue where serialising data structures containing
derivations to JSON would fail.
Change-Id: I5c39e3d8356ee93a07eda481410f88610f6dd9f8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8209
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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This adds static strings to generator frames that describe the
generator in a human-readable fashion, which are then logged in
observers.
This makes runtime traces very precise, explaining exactly what is
being requested from where.
Change-Id: I695659a6bd0b7b0bdee75bc8049651f62b150e0c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8206
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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It turns out that this is used not just in coerceToString, but also in
toJSON.
Change-Id: I1c324b115a0b8bb6d83446d5bf70453c9b90685e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8203
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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This shaves another 8 bytes off Value. How did that type get so big?!
Change-Id: I65e9b59a1636bd57e3cc4aec5fea16887070b832
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8153
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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No longer needed, and in some cases caused some extra work.
Change-Id: I64e8e7292573bdc92a9c7a8e470e33f8c526f311
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8152
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Instead of the two different representations (which we don't really
use much), use a `Box<str>` (which potentially shaves another 8 bytes
off `Value`).
NixString values themselves are immutable anyways (which was a
guarantee we already had with `SmolStr`), so this doesn't change
anything else.
Change-Id: I1d8454c056c21ecb0aebc473cfb3ae06cd70dbb6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8151
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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The size of a `Vector<Value>` is 64 *bytes*, which is quite large, and
it bloated the entire Value type to this size.
This change adds an indirection for the inner vector through Rc.
Initially I tried to use a Box, but this breaks pointer equality
guarantees for the Vector when it is small enough to be inlined.
This reduces the size of Value from 64 to 32 bytes.
Change-Id: Ic3211e861b1966c78b2c3d536ba291fea92647fd
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8150
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Warning: This is probably the biggest refactor in tvix-eval history,
so far.
This replaces all instances of trampolines and recursion during
evaluation of the VM loop with generators. A generator is an
asynchronous function that can be suspended to yield a message (in our
case, vm::generators::GeneratorRequest) and receive a
response (vm::generators::GeneratorResponsee).
The `genawaiter` crate provides an interpreter for generators that can
drive their execution and lets us move control flow between the VM and
suspended generators.
To do this, massive changes have occured basically everywhere in the
code. On a high-level:
1. The VM is now organised around a frame stack. A frame is either a
call frame (execution of Tvix bytecode) or a generator frame (a
running or suspended generator).
The VM has an outer loop that pops a frame off the frame stack, and
then enters an inner loop either driving the execution of the
bytecode or the execution of a generator.
Both types of frames have several branches that can result in the
frame re-enqueuing itself, and enqueuing some other work (in the
form of a different frame) on top of itself. The VM will eventually
resume the frame when everything "above" it has been suspended.
In this way, the VM's new frame stack takes over much of the work
that was previously achieved by recursion.
2. All methods previously taking a VM have been refactored into async
functions that instead emit/receive generator messages for
communication with the VM.
Notably, this includes *all* builtins.
This has had some other effects:
- Some test have been removed or commented out, either because they
tested code that was mostly already dead (nix_eq) or because they
now require generator scaffolding which we do not have in place for
tests (yet).
- Because generator functions are technically async (though no async
IO is involved), we lose the ability to use much of the Rust
standard library e.g. in builtins. This has led to many algorithms
being unrolled into iterative versions instead of iterator
combinations, and things like sorting had to be implemented from scratch.
- Many call sites that previously saw a `Result<..., ErrorKind>`
bubble up now only see the result value, as the error handling is
encapsulated within the generator loop.
This reduces number of places inside of builtin implementations
where error context can be attached to calls that can fail.
Currently what we gain in this tradeoff is significantly more
detailed span information (which we still need to bubble up, this
commit does not change the error display).
We'll need to do some analysis later of how useful the errors turn
out to be and potentially introduce some methods for attaching
context to a generator frame again.
This change is very difficult to do in stages, as it is very much an
"all or nothing" change that affects huge parts of the codebase. I've
tried to isolate changes that can be isolated into the parent CLs of
this one, but this change is still quite difficult to wrap one's mind
and I'm available to discuss it and explain things to any reviewer.
Fixes: b/238, b/237, b/251 and potentially others.
Change-Id: I39244163ff5bbecd169fe7b274df19262b515699
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8104
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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Adds a `Value::neo_nix_eq` method (the `neo_` prefix will be dropped
when we flip over to the generator implementation of the VM) which
implements Nix equality semantics using async, generator-based
comparisons.
Instead of tracking the "kind" of equality that is being compared (see
the pointer-equality doc) through a pair of booleans, I've introduced
an enum that explicitly lists the possible comparisons.
Change-Id: I3354cc1470eeccb3000a5ae24f2418db1a7a2edc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8241
Tested-by: BuildkiteCI
Reviewed-by: Adam Joseph <adam@westernsemico.com>
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In order to implement an asynchronous builtins.sort (required for
moving builtins to generators), we need an `async` sorting algorithm
as our comparators involve invoking a Nix function.
This commit implements a fairly simple, optimised bubble sort as the
sorting algorithm used in our `async fn sort_by`.
There don't seem to be any crates providing async versions of things
like this, and they might actually be pretty hard to implement
generically due to some constraints about how `async` works.
Note that this algorithm is less efficient than the hybrid
"timsort/mergesort/insert sort" used in the Rust standard library. I
tried to write a merge sort implementation, but ran into isuses with
the sort becoming unstable because our comparators can not yield
equality. This is the simplest implementation which I know to be
correct.
Note that as of this commit this is *not* covered by the Tvix test
suite, but it will be as soon as the rest of the generator code lands.
Change-Id: Ia9a604f7dd941d6acc9212c902e0e637ed75bebc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8239
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Tested-by: BuildkiteCI
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This module contains the request/response types for generators
requesting actions from the VM.
For most of these, an async helper function is added that will be used
inside of generator functions to make use of these requests/responses
instead of constructing them directly.
Change-Id: I1e085f88adaf784a34867957a0e82532d3a83d7c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8148
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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Because they do not use it, and it can not be passed with the coming
generator refactoring.
Change-Id: I0d96f2357a7ee79cd8a0f401583d4286230d4a6b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8146
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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This is a ThunkSet wrapped to be shareable, which will be required
once ThunkSets are embedded in futures.
Change-Id: I5a067b7972ac86e4d354c75ef05c86b2284c1137
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8144
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
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Change-Id: Iea248870a0ea5d38cb02ff059c968fbd563570b6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8143
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Again simplifying some code down the line, where bits of code that
construct attribute sets already have the final structure available.
Change-Id: I0bb7a1daa63298122b51be73d35d695a4f73f8b0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8140
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Tested-by: BuildkiteCI
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Change-Id: I4c02f0104c455ac00a3f299c1fbf75cbb08e8972
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8142
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Autosubmit: tazjin <tazjin@tvl.su>
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Change-Id: Ifb59ef148ea4fab613f2e4efb133c04baafa3a98
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8141
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
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This adds addresses of thunk and closure chunks to the debug output
displayed when dumping bytecode.
This makes it possible to see in the dump which thunks are referenced
by constants in other thunks.
Change-Id: I2c98de5227e7cb415666cd3134c947a56979dc80
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8137
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
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This CL removes redundant clone from value which is
going to be dropped without further use.
Change-Id: Ibd2a724853c5cfbf8ca40bf0b3adf0fab89b9be5
Signed-off-by: Aaqa Ishtyaq <aaqaishtyaq@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8125
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
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