This makes it possible to build with -DGC_DEBUG.

This reduces the risk of object liveness misdetection. For example,
Glibc has an internal variable "mp_" that often points to a Boehm
object, keeping it alive unnecessarily. Since we don't store any
actual roots in global variables, we can just disable data segment
scanning.

With this, the max RSS doing 100 evaluations of
nixos.tests.firefox.x86_64-linux.drvPath went from 718 MiB to 455 MiB.

This prevents EvalState::resetFileCache() from parsing everything all
over again.

Fix #2162: use getaddrinfo instead of curl to preload NSS

libstore/gc.cc: ignore ESRCH when reading /proc

If a process disappears between the time /proc/[pid]/maps is opened and
the time it is read, the read() syscall will return ESRCH. This should be ignored.

tests: more robust check for user namespaces availability (canUseSand…

manual: builtins.fromJSON: remove the claim that floats are not allowed

floating-point numbers are supported now, including the fromJSON
builtin. Reported on IRC by inquisitiv3

use debug instead of printTalkative to avoid spamming hydra queue-runner

runner logs.

Dockerfile: 2.0.4

Issue https://github.com/NixOS/nix/issues/2165

I'm not sure if curl ever asks for enough data at once
for truncation to occur but better safe than sorry.

Don't say "download" when we mean "upload".

Note: this means that for those doing 'curl | sh', you can now pin a
specific version, e.g.

  curl https://nixos.org/releases/nix/nix-2.0.4/install | sh

https://nixos.org/nix/{install,install.sig} are now just symlinks to
the corresponding files in the latest release directory.

Implement --delete-generations + flag for keeping last N number of gens

Nix profile & installation: handle set -u installations

If the profile is sourced inside a script with `set -u`, the check for
__ETC_PROFILE_NIX_SOURCED and NIX_SSL_CERT_FILE would raise an error.
A simple guard around this check allows the script to operate under
standard environments (where it is fairly reasonable to assume USER
and HOME are set.)

Explain fetchTarball timeout behavior in the doc

E.g.

  nix-build --store ~/my-nix/ -E 'import <nix/fetchurl.nix> { url = https://cache.nixos.org/nar/0nwi996rgq4b914qyx0mv2wq4k80hjac7xilikavagw7kxmn2iiv.nar.xz; sha256 = "0nwi996rgq4b914qyx0mv2wq4k80hjac7xilikavagw7kxmn2iiv"; }'

now runs in 17 MiB (was 70 MiB), while

  nix-build --store ~/my-nix/ -E 'import <nix/fetchurl.nix> { url = https://cache.nixos.org/nar/0nwi996rgq4b914qyx0mv2wq4k80hjac7xilikavagw7kxmn2iiv.nar.xz; sha256 = "0d2fxljdih3nc5dqx41hjzic3141ajil94m8kdbpryq569dpsbvb"; unpack = true; }'

runs in 17 MiB (was 346 MiB).