From Postfix documentation:
With this setting, the Postfix SMTP server will not reject mail with "User
unknown in local recipient table". Don't do this on systems that receive mail
directly from the Internet. With today's worms and viruses, Postfix will become
a backscatter source: it accepts mail for non-existent recipients and then
tries to return that mail as "undeliverable" to the often forged sender
address.
The callCabal2nix function cannot reliably determine the appropriate "name" for
the package it's processing. Attempts to derive this information have led to
plenty of evaluation errors, and so I'd like to go for the obvious and reliable
solution now and let the caller specify that bit of information.
Here is an example that demonstrates how to use callCabal2nix.
let
pkgs = import <nixpkgs> {};
src = pkgs.fetchFromGitHub {
owner = "gtk2hs";
repo = "gtk2hs";
rev = "eee61d84edf1dd44f8d380d7d7cae2405de50124";
sha256 = "12i53grimni0dyjqjydl120z5amcn668w4pfhl8dxscjh4a0l5nb";
};
in
pkgs.haskellPackages.callCabal2nix "gtkhs-tools" "${src}/tools" {}
This fixes the "sliding window" principle:
0. Run packages: build = native; host = foreign; target = foreign;
1. Build packages: build = native; host = native; target = foreign;
2. Vanilla packages: build = native; host = native; target = native;
3. Vanilla packages: build = native; host = native; target = native;
n+3. ...
Each stage's build dependencies are resolved against the previous stage,
and the "foreigns" are shifted accordingly. Vanilla packages alone are
built against themsevles, since there are no more "foreign"s to shift away.
Before, build packages' build dependencies were resolved against
themselves:
0. Run packages: build = native; host = foreign; target = foreign;
1. Build packages: build = native; host = native; target = foreign;
2. Build packages: build = native; host = native; target = foreign;
n+2. ...
This is wrong because that principle is violated by the target
platform staying foreign.
This will change the hashes of many build packages and run packages, but
that is OK. This is an unavoidable cost of fixing cross compiling.
The cross compilation docs have been updated to reflect this fix.
