This replaces the 'patches' argument to builtins.fetchTree with
something more generic. So instead of 'builtins.fetchTree { patches =
... }' you can do 'builtins.patch { src = builtins.fetchTree { ... };
patchFiles = ... }'.
this slightly increases the amount of memory used for any given symbol, but this
increase is more than made up for if the symbol is referenced more than once in
the EvalState that holds it. on average every symbol should be referenced at
least twice (once to introduce a binding, once to use it), so we expect no
increase in memory on average.
symbol tables are limited to 2³² entries like position tables, and similar
arguments apply to why overflow is not likely: 2³² symbols would require as many
string instances (at 24 bytes each) and map entries (at 24 bytes or more each,
assuming that the map holds on average at most one item per bucket as the docs
say). a full symbol table would require at least 192GB of memory just for
symbols, which is well out of reach. (an ofborg eval of nixpks today creates
less than a million symbols!)
Pos objects are somewhat wasteful as they duplicate the origin file name and
input type for each object. on files that produce more than one Pos when parsed
this a sizeable waste of memory (one pointer per Pos). the same goes for
ptr<Pos> on 64 bit machines: parsing enough source to require 8 bytes to locate
a position would need at least 8GB of input and 64GB of expression memory. it's
not likely that we'll hit that any time soon, so we can use a uint32_t index to
locate positions instead.
You can now write
fetchTree {
type = "github";
owner = "NixOS";
repo = "nixpkgs";
rev = "0f316e4d72daed659233817ffe52bf08e081b5de";
patches = [ ./thunderbird-1.patch ./thunderbird-2.patch ];
};
to apply a list of patches to a tree. These are applied lazily - the
patched tree is not materialized unless you do something that causes
the entire tree to be copied to the store (like 'src = fetchTree {
... }'). The equivalent of '-p1' is implied.
File additions/deletions/renames are not yet handled.
Issue #3920.
This allows closures to be imported at evaluation time, without
requiring the user to configure substituters. E.g.
builtins.fetchClosure {
storePath = /nix/store/f89g6yi63m1ywfxj96whv5sxsm74w5ka-python3.9-sqlparse-0.4.2;
from = "https://cache.ngi0.nixos.org";
}
1. `DerivationOutput` now as the `std::variant` as a base class. And the
variants are given hierarchical names under `DerivationOutput`.
In 8e0d0689be @matthewbauer and I
didn't know a better idiom, and so we made it a field. But this sort
of "newtype" is anoying for literals downstream.
Since then we leaned the base class, inherit the constructors trick,
e.g. used in `DerivedPath`. Switching to use that makes this more
ergonomic, and consistent.
2. `store-api.hh` and `derivations.hh` are now independent.
In bcde5456cc I swapped the dependency,
but I now know it is better to just keep on using incomplete types as
much as possible for faster compilation and good separation of
concerns.
This was introduced in #6174. However fetch{url,Tarball} are legacy
and we shouldn't have an undocumented attribute that does the same
thing as one that already exists ('sha256').
