[WIP] Build nixpkgs with gcc 8 by default

.github/CODEOWNERS

@@ -139,3 +139,14 @@
 
 # Bazel
 /pkgs/development/tools/build-managers/bazel @mboes @Profpatsch
+
+# NixOS modules for e-mail and dns services
+/nixos/modules/services/mail/mailman.nix    @peti
+/nixos/modules/services/mail/postfix.nix    @peti
+/nixos/modules/services/networking/bind.nix @peti
+/nixos/modules/services/mail/rspamd.nix     @peti
+
+# Emacs
+/pkgs/applications/editors/emacs-modes @adisbladis
+/pkgs/applications/editors/emacs       @adisbladis
+/pkgs/top-level/emacs-packages.nix     @adisbladis

doc/languages-frameworks/android.section.md

@@ -185,10 +185,9 @@ with import <nixpkgs> {};
 
 androidenv.emulateApp {
   name = "emulate-MyAndroidApp";
-  platformVersion = "24";
-  abiVersion = "armeabi-v7a"; # mips, x86 or x86_64
-  systemImageType = "default";
-  useGoogleAPIs = false;
+  platformVersion = "28";
+  abiVersion = "x86_64"; # armeabi-v7a, mips, x86
+  systemImageType = "google_apis_playstore";
 }
 ```
 
@@ -201,7 +200,7 @@ with import <nixpkgs> {};
 androidenv.emulateApp {
   name = "emulate-MyAndroidApp";
   platformVersion = "24";
-  abiVersion = "armeabi-v7a"; # mips, x86 or x86_64
+  abiVersion = "armeabi-v7a"; # mips, x86, x86_64
   systemImageType = "default";
   useGoogleAPIs = false;
   app = ./MyApp.apk;

doc/languages-frameworks/crystal.section.md

@@ -0,0 +1,71 @@
+# Crystal
+
+## Building a Crystal package
+
+This section uses [Mint](https://github.com/mint-lang/mint) as an example for how to build a Crystal package.
+
+If the Crystal project has any dependencies, the first step is to get a `shards.nix` file encoding those. Get a copy of the project and go to its root directory such that its `shard.lock` file is in the current directory, then run `crystal2nix` in it
+```bash
+$ git clone https://github.com/mint-lang/mint
+$ cd mint
+$ git checkout 0.5.0
+$ nix-shell -p crystal2nix --run crystal2nix
+```
+
+This should have generated a `shards.nix` file.
+
+Next create a Nix file for your derivation and use `pkgs.crystal.buildCrystalPackage` as follows:
+```nix
+with import <nixpkgs> {};
+crystal.buildCrystalPackage rec {
+  pname = "mint";
+  version = "0.5.0";
+
+  src = fetchFromGitHub {
+    owner = "mint-lang";
+    repo = "mint";
+    rev = version;
+    sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
+  };
+
+  # Insert the path to your shards.nix file here
+  shardsFile = ./shards.nix;
+
+  ...
+}
+```
+
+This won't build anything yet, because we haven't told it what files build. We can specify a mapping from binary names to source files with the `crystalBinaries` attribute. The project's compilation instructions should show this. For Mint, the binary is called "mint", which is compiled from the source file `src/mint.cr`, so we'll specify this as follows:
+
+```nix
+  crystalBinaries.mint.src = "src/mint.cr";
+
+  # ...
+```
+
+Additionally you can override the default `crystal build` options (which are currently `--release --progress --no-debug --verbose`) with
+
+```nix
+  crystalBinaries.mint.options = [ "--release" "--verbose" ];
+```
+
+Depending on the project, you might need additional steps to get it to compile successfully. In Mint's case, we need to link against openssl, so in the end the Nix file looks as follows:
+
+```nix
+with import <nixpkgs> {};
+crystal.buildCrystalPackage rec {
+  version = "0.5.0";
+  pname = "mint";
+  src = fetchFromGitHub {
+    owner = "mint-lang";
+    repo = "mint";
+    rev = version;
+    sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
+  };
+
+  shardsFile = ./shards.nix;
+  crystalBinaries.mint.src = "src/mint.cr";
+
+  buildInputs = [ openssl_1_0_2 ];
+}
+```

doc/languages-frameworks/index.xml

@@ -32,4 +32,5 @@
  <xi:include href="titanium.section.xml" />
  <xi:include href="vim.section.xml" />
  <xi:include href="emscripten.section.xml" />
+ <xi:include href="crystal.section.xml" />
 </chapter>

doc/languages-frameworks/perl.xml

@@ -75,7 +75,8 @@ foo = import ../path/to/foo.nix {
      It adds the contents of the <envar>PERL5LIB</envar> environment variable
      to <literal>#! .../bin/perl</literal> line of Perl scripts as
      <literal>-I<replaceable>dir</replaceable></literal> flags. This ensures
-     that a script can find its dependencies.
+     that a script can find its dependencies. (This can cause this shebang line
+     to become too long for Darwin to handle; see the note below.)
     </para>
    </listitem>
    <listitem>
@@ -137,6 +138,36 @@ ClassC3Componentised = buildPerlPackage rec {
 </programlisting>
  </para>
 
+ <para>
+  On Darwin, if a script has too many
+  <literal>-I<replaceable>dir</replaceable></literal> flags in its first line
+  (its “shebang line”), it will not run. This can be worked around by calling
+  the <literal>shortenPerlShebang</literal> function from the
+  <literal>postInstall</literal> phase:
+<programlisting>
+{ stdenv, buildPerlPackage, fetchurl, shortenPerlShebang }:
+
+ImageExifTool = buildPerlPackage {
+  pname = "Image-ExifTool";
+  version = "11.50";
+
+  src = fetchurl {
+    url = "https://www.sno.phy.queensu.ca/~phil/exiftool/Image-ExifTool-11.50.tar.gz";
+    sha256 = "0d8v48y94z8maxkmw1rv7v9m0jg2dc8xbp581njb6yhr7abwqdv3";
+  };
+
+  buildInputs = stdenv.lib.optional stdenv.isDarwin shortenPerlShebang;
+  postInstall = stdenv.lib.optional stdenv.isDarwin ''
+    shortenPerlShebang $out/bin/exiftool
+  '';
+};
+</programlisting>
+ This will remove the <literal>-I</literal> flags from the shebang line,
+ rewrite them in the <literal>use lib</literal> form, and put them on the next
+ line instead. This function can be given any number of Perl scripts as
+ arguments; it will modify them in-place.
+ </para>
+
  <section xml:id="ssec-generation-from-CPAN">
   <title>Generation from CPAN</title>