Unsetting `build-users-group` (without `auto-allocate-uids` enabled)
gives the following error:
```
src/libstore/lock.cc:25: static std::unique_ptr<nix::UserLock> nix::SimpleUserLock::acquire(): Assertion `settings.buildUsersGroup != ""' failed.
```
Fix the logic in `useBuildUsers` and document the default value
for `build-users-group`.
This makes the position object used in exceptions abstract, with a
method getSource() to get the source code of the file in which the
error originated. This is needed for lazy trees because source files
don't necessarily exist in the filesystem, and we don't want to make
libutil depend on the InputAccessor type in libfetcher.
Make everything be in the form "while ..." (most things were already),
and in particular *don't* use other propositions that must go after or
before specific "while ..." clauses to make sense.
When debugging nix expressions the outermost trace tends to be more useful
than the innermost. It is therefore printed last to save developers from
scrolling.
We used to set enforceDeterminism to true in the settings (by default)
and thus did send a non-zero value over the wire. The value should
probably be ignored as it should only matter if nrRounds is non-zero
as well.
Having the old code here where the value is expected to be zero only
works with the same version of Nix where we are sending zero. We
should always test this against older Nix versions being client or
server as otherwise upgrade in larger networks might be a pain.
Fixes 8e0946e8df
These only functioned if a very narrow combination of conditions held:
- The result path does not yet exist (--check did not result in
repeated builds), AND
- The result path is not available from any configured substituters, AND
- No remote builders that can build the path are available.
If any of these do not hold, a derivation would be built 0 or 1 times
regardless of the repeat option. Thus, remove it to avoid confusion.
The old way was not correct.
Here is an example:
```
$ nix-instantiate --eval --expr 'let x = a: throw "asdf"; in x 1' --show-trace
error: asdf
… while evaluating 'x'
at «string»:1:9:
1| let x = a: throw "asdf"; in x 1
| ^
… from call site
at «string»:1:29:
1| let x = a: throw "asdf"; in x 1
| ^
```
and yet also:
```
$ nix-instantiate --eval --expr 'let x = a: throw "asdf"; in x' --show-trace
<LAMBDA>
```
Here is the thing: in both cases we are evaluating `x`!
Nix is a higher-order languages, and functions are a sort of value. When
we write `x = a: ...`, `a: ...` is the expression that `x` is being
defined to be, and that is already a value. Therefore, we should *never*
get an trace that says "while evaluating `x`", because evaluating `a:
...` is *trival* and nothing happens during it!
What is actually happening here is we are applying `x` and evaluating
its *body* with arguments substituted for parameters. I think the
simplest way to say is just "while *calling* `x`", and so that is what I
changed it to.
We need to close the GC server socket before shutting down the active
GC client connections, otherwise a client may (re)connect and get
ECONNRESET. But also handle ECONNRESET for resilience.
Fixes random failures like
GC socket disconnected
connecting to '/tmp/nix-shell.y07M0H/nix-test/default/var/nix/gc-socket/socket'
sending GC root '/tmp/nix-shell.y07M0H/nix-test/default/store/kb5yzija0f1x5xkqkgclrdzldxj6nnc6-non-blocking'
reading GC root from client: error: unexpected EOF reading a line
1 store paths deleted, 0.00 MiB freed
error: reading from file: Connection reset by peer
in gc-non-blocking.sh.
It calls strlen() on the input (rather than simply copying at most
`size` bytes), which can fail if the input is not zero-terminated and
is inefficient in any case.
Fixes#7347.
why-depends assumed that we knew the output path of the second argument.
For CA derivations, we might not know until it's built. One way to solve
this would be to build the second installable to get the output path.
In this case we don't need to, though. If the first installable (A)
depends on the second (B), then getting the store path of A will
necessitate having the store path B. The contrapositive is, if the store
path of B is not known (i.e. it's a CA derivation which hasn't been
built), then A does not depend on B.
We shouldn't skip this if the supplementary group list is empty,
because then the sandbox won't drop the supplementary groups of the
parent (like "root").
The new experimental feature 'cgroups' enables the use of cgroups for
all builds. This allows better containment and enables setting
resource limits and getting some build stats.
Linus Heckemann
Jörg Thalheim
Yorick