Remove outdated and no longer relevant TODO. It's more confusing
now, since symbol table must now be addressed by uint32_t indices
in order to keep Attr size down to 16 bytes on 64 bit machines.
The intention is to switch to transparent comparators from N3657 for
ordered set containers for strings and using the alias consistently
would simplify things.
This trades off some executable size for measurable lexer performance
improvements.
Note on the explicitly enabling 8bit scanner.
This is needed due to the default behavior of flex (excerpt from the manual [1]):
> Flex’s default behavior is to generate an 8-bit scanner unless you
> use the ‘-Cf’ or ‘-CF’, in which case flex defaults to generating
> 7-bit scanners unless your site was always configured to generate 8-bit
> scanners.
Some quantifyable metrics:
Nixpkgs revision: a6e3f45acf4e817532a861ab0eda4ab5485fecc1
Parsing the largest file in nixpkgs: pkgs/development/haskell-modules/hackage-packages.nix.
(Before this patch)
```
$ nix build github:nixos/nix/9fe3077d4#nix-expr
$ du --apparent-size result/lib/libnixexpr.so
2518 result/lib/libnixexpr.so
$ nix build github:nixos/nix/9fe3077d4#nix-cli
$ taskset -c 2,3 hyperfine "GC_INITIAL_HEAP_SIZE=16g \
result/bin/nix-instantiate --parse \
../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix > /dev/null"
Time (mean ± σ): 375.5 ms ± 6.3 ms [User: 316.9 ms, System: 56.7 ms]
Range (min … max): 368.5 ms … 388.3 ms 10 runs
```
(After the patch)
```
$ nix build .#nix-expr
$ du --apparent-size result/lib/libnixexpr.so
2685 result/lib/libnixexpr.so
$ nix build .#nix-cli
$ taskset -c 2,3 hyperfine "GC_INITIAL_HEAP_SIZE=16g \
result/bin/nix-instantiate --parse \
../nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix > /dev/null"
Time (mean ± σ): 326.8 ms ± 4.9 ms [User: 269.5 ms, System: 55.3 ms]
Range (min … max): 319.7 ms … 335.5 ms 10 runs
```
Overall, the change is roughly:
- 2518KiB -> 2685KiB ~ 150 KiB of machine code
- 375ms -> 325ms ~ 50ms
The perf uplift for eval-heavy test cases is obviously less noticeable,
but it doesn't make sense not to take this free perf win.
[1]: https://westes.github.io/flex/manual/Options-Affecting-Scanner-Behavior.html#Options-Affecting-Scanner-Behavior
Rather than "mounting" the store inside an empty virtual filesystem,
just return the store as a virtual filesystem. This is more modular.
(FWIW, it also supports two long term hopes of mind:
1. More capability-based Nix language mode. I dream of a "super pure
eval" where you can only use relative path literals (See #8738), and
any `fetchTree`-fetched stuff + the store are all disjoint (none is
mounted in another) file systems.
2. Windows, where the store dir may include drive letters, etc., and is
thus unsuitable to be the prefix of any `CanonPath`s.
)
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Revert most of "Hack together a fix for the public headers"
- The `libmain` change is kept, and one more libmain change is made.
(Need to update Meson and Nix per the package alike).
- The S3 situation is fixed in a different way: the variable is public
now, used in the header, and fixed accordingly.
- Fix TODO for `HAVE_EMBEDDED_SANDBOX_SHELL`
This reverts commit 2b51250534.
For example, instead of doing
#include "nix/store-config.hh"
#include "nix/derived-path.hh"
Now do
#include "nix/store/config.hh"
#include "nix/store/derived-path.hh"
This was originally planned in the issue, and also recent requested by
Eelco.
Most of the change is purely mechanical. There is just one small
additional issue. See how, in the example above, we took this
opportunity to also turn `<comp>-config.hh` into `<comp>/config.hh`.
Well, there was already a `nix/util/config.{cc,hh}`. Even though there
is not a public configuration header for libutil (which also would be
called `nix/util/config.{cc,hh}`) that's still confusing, To avoid any
such confusion, we renamed that to `nix/util/configuration.{cc,hh}`.
Finally, note that the libflake headers already did this, so we didn't
need to do anything to them. We wouldn't want to mistakenly get
`nix/flake/flake/flake.hh`!
Progress on #7876
There are two big changes:
1. Public and private config is now separated. Configuration variables
that are only used internally do not go in a header which is
installed.
(Additionally, libutil has a unix-specific private config header,
which should only be used in unix-specific code. This keeps things a
bit more organized, in a purely private implementation-internal way.)
2. Secondly, there is no more `-include`. There are very few config
items that need to be publically exposed, so now it is feasible to
just make the headers that need them just including the (public)
configuration header.
And there are also a few more small cleanups on top of those:
- The configuration files have better names.
- The few CPP variables that remain exposed in the public headers are
now also renamed to always start with `NIX_`. This ensures they should
not conflict with variables defined elsewhere.
- We now always use `#if` and not `#ifdef`/`#ifndef` for our
configuration variables, which helps avoid bugs by requiring that
variables must be defined in all cases.
The short answer for why we need to do this is so we can consistently do
`#include "nix/..."`. Without this change, there are ways to still make
that work, but they are hacky, and they have downsides such as making it
harder to make sure headers from the wrong Nix library (e..g.
`libnixexpr` headers in `libnixutil`) aren't being used.
The C API alraedy used `nix_api_*`, so its headers are *not* put in
subdirectories accordingly.
Progress on #7876
We resisted doing this for a while because it would be annoying to not
have the header source file pairs close by / easy to change file
path/name from one to the other. But I am ameliorating that with
symlinks in the next commit.
We rely on `yyerror()` instead.
> The variable yynerrs contains the number of syntax errors reported so
> far.
> Normally this variable is global; but if you request a pure parser
> (see A Pure (Reentrant) Parser) then it is a local variable which only
> the actions can access.
https://www.gnu.org/software/bison/manual/html_node/Error-Reporting-Function.html
The underlying issue is that debugger code path was
calling PosTable::operator[] in each eval method.
This has become incredibly expensive since 5d9fdab3de.
While we are it it, I've reworked the code to
not use std::shared_ptr where it really isn't necessary.
As I've documented in previous commits, this is actually
more a workaround for recursive header dependencies now
and is only necessary in `error.hh` code.
Some ad-hoc benchmarking:
After this commit:
```
Benchmark 1: nix eval nixpkgs#hello --impure --ignore-try --no-eval-cache --debugger
Time (mean ± σ): 784.2 ms ± 7.1 ms [User: 561.4 ms, System: 147.7 ms]
Range (min … max): 773.5 ms … 792.6 ms 10 runs
```
On master 3604c7c51:
```
Benchmark 1: nix eval nixpkgs#hello --impure --ignore-try --no-eval-cache --debugger
Time (mean ± σ): 22.914 s ± 0.178 s [User: 18.524 s, System: 4.151 s]
Range (min … max): 22.738 s … 23.290 s 10 runs
```
All of this code doesn't actually depend on anything from
libexpr. Because Pos is so tigtly coupled with Error, it
makes sense to have in the same library.
This fixes a few of the property tests, now that the property tests
are actually generating arbitrary data - some of that data now
requiring experimental features to function properly.
It's not very clear what the ownership model is here, but one thing
is certain: `.up` can't be destroyed before the StaticEnv that refers
to it is.
Changing a non-owning pointer to taking shared ownership of the parent
`StaticEnv` prevents the `.up` from being freed.
I'm not a huge fan of the inverted ownership, where child `StaticEnv`
takes a refcount of the parent, but this seems like the least intrusive
way to fix the use-after-free.
This shouldn't cause any shared_ptr cycles to appear (hopefully).
Note that in pure mode, we don't need to use the union FS even when
using a chroot store, since the user shouldn't have access to the
physical /nix/store.
