From ea02729ebd784729d5028e5051512c7b3f92ab3e Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walther@technowledgy.de>
Date: Sun, 4 Feb 2024 17:37:51 +0100
Subject: [PATCH] nix: Use -split-sections with pkgsStatic to make static
 executable smaller again

This works around https://github.com/NixOS/nixpkgs/issues/286285 to use -split-sections
in a cross-compiling scenario. This will reduce the size of the static executable and also
remove the remaining references to /nix/store/.. reducing closure size dramatically.

This also fixes the docker image blowing up in size since we switched to pkgsStatic.
---
 default.nix                    | 10 ++++++++--
 nix/split-sections-cross.patch | 14 ++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)
 create mode 100644 nix/split-sections-cross.patch

diff --git a/default.nix b/default.nix
index 6cf227b66a..426464a256 100644
--- a/default.nix
+++ b/default.nix
@@ -28,6 +28,12 @@ let
       sha256 = nixpkgsVersion.tarballHash;
     };
 
+  nixpkgs-patched = (import nixpkgs { inherit overlays system; }).applyPatches {
+    name = "nixpkgs-patched";
+    src = nixpkgs;
+    patches = [ nix/split-sections-cross.patch ];
+  };
+
   allOverlays =
     import nix/overlays;
 
@@ -46,7 +52,7 @@ let
 
   # Evaluated expression of the Nixpkgs repository.
   pkgs =
-    import nixpkgs { inherit overlays system; };
+    import nixpkgs-patched { inherit overlays system; };
 
   postgresqlVersions =
     [
@@ -82,7 +88,7 @@ let
   inherit (pkgs.haskell) lib;
 in
 rec {
-  inherit nixpkgs pkgs;
+  inherit nixpkgs-patched pkgs;
 
   # Derivation for the PostgREST Haskell package, including the executable,
   # libraries and documentation. We disable running the test suite on Nix
diff --git a/nix/split-sections-cross.patch b/nix/split-sections-cross.patch
new file mode 100644
index 0000000000..22d1fc59dc
--- /dev/null
+++ b/nix/split-sections-cross.patch
@@ -0,0 +1,14 @@
+This works around https://github.com/NixOS/nixpkgs/issues/286285 by passing --enable-split-sections instead of ghc-options.
+---
+--- a/pkgs/development/haskell-modules/generic-builder.nix
++++ b/pkgs/development/haskell-modules/generic-builder.nix
+@@ -245,8 +245,7 @@ let
+     (enableFeature doBenchmark "benchmarks")
+     "--enable-library-vanilla"  # TODO: Should this be configurable?
+     (enableFeature enableLibraryForGhci "library-for-ghci")
+-  ] ++ optionals (enableDeadCodeElimination && (lib.versionOlder "8.0.1" ghc.version)) [
+-     "--ghc-option=-split-sections"
++    (enableFeature enableDeadCodeElimination "split-sections")
+   ] ++ optionals dontStrip [
+     "--disable-library-stripping"
+     "--disable-executable-stripping"