From e819e1a63120b984da408c167aa3c4bdf1880b7d Mon Sep 17 00:00:00 2001
From: Alex Auvolat <lx@deuxfleurs.fr>
Date: Sat, 1 Feb 2025 23:22:13 +0100
Subject: [PATCH] cross compilation seems to work

---
 .cargo/config.toml |  6 +++---
 nix/compile.nix    | 51 ++++++++++++++++++++++++++++++++++++----------
 2 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/.cargo/config.toml b/.cargo/config.toml
index d29d6c33..7e2ad9f3 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -1,3 +1,3 @@
-[target.x86_64-unknown-linux-gnu]
-linker = "clang"
-rustflags = ["-C", "link-arg=-fuse-ld=mold"]
+#[target.x86_64-unknown-linux-gnu]
+#linker = "clang"
+#rustflags = ["-C", "link-arg=-fuse-ld=mold"]
diff --git a/nix/compile.nix b/nix/compile.nix
index 7520a271..ad068c21 100644
--- a/nix/compile.nix
+++ b/nix/compile.nix
@@ -15,18 +15,34 @@
 let
   log = v: builtins.trace v v;
 
-  pkgs =
+  targetEnvMap = {
+        "armv6l-unknown-linux-musleabihf" = "ARMV6L_UNKNOWN_LINUX_MUSLEABIHF";
+        "aarch64-unknown-linux-musl" = "AARCH64_UNKNOWN_LINUX_MUSL";
+        "i686-unknown-linux-musl" = "I686_UNKNOWN_LINUX_MUSL";
+        "x86_64-unknown-linux-musl" = "X86_64_UNKNOWN_LINUX_MUSL";
+      };
+
+  pkgs = if target != null then
+    import nixpkgs {
+      inherit system;
+      crossSystem = {
+        config = target;
+        isStatic = true;
+      };
+      overlays = [ (import rust-overlay) ];
+    }
+  else
     import nixpkgs {
       inherit system;
       overlays = [ (import rust-overlay) ];
     };
 
-  inherit (pkgs) lib;
+  inherit (pkgs) lib stdenv;
 
-  toolchain = pkgs.symlinkJoin {
+  toolchain = (p: p.symlinkJoin {
     name = "garage-rust-toolchain-1.78";
     paths = [
-      (pkgs.rust-bin.stable."1.78.0".default.override {
+      (p.rust-bin.stable."1.78.0".default.override {
         targets = [
           "arm-unknown-linux-musleabihf"
           "aarch64-unknown-linux-musl"
@@ -38,11 +54,12 @@ let
           "rustfmt"
         ];
       })
-      pkgs.clang
-      pkgs.mold
-      pkgs.protobuf
+      p.protobuf
+    ] ++ lib.optionals (target == null) [
+      # p.clang
+      # p.mold
     ];
-  };
+  });
 
   craneLib = (crane.mkLib pkgs).overrideToolchain toolchain;
 
@@ -100,7 +117,7 @@ let
     target;
 
   codegenOpts = if target != null then codegenOptsMap.${target} else [
-    "link-args=-fuse-ld=mold"
+    # "link-args=-fuse-ld=mold"
   ];
 
   commonArgs =
@@ -112,6 +129,11 @@ let
       strictDeps = true;
       cargoExtraArgs = "--features ${featuresStr}";
 
+      nativeBuildInputs = with pkgs; [
+        pkg-config
+        stdenv.cc
+      ];
+
       GIT_VERSION = git_version;
 
       CARGO_PROFILE = if release then "release" else "dev";
@@ -123,10 +145,17 @@ let
   //
     (if rustTarget != null then {
       CARGO_BUILD_TARGET = rustTarget;
-    } else {});
+
+      "CARGO_TARGET_${targetEnvMap.${target}}_LINKER" = "${stdenv.cc.targetPrefix}cc";
+
+      HOST_CC = "${stdenv.cc.nativePrefix}cc";
+      TARGET_CC = "${stdenv.cc.targetPrefix}cc";
+    } else {
+      # CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER = "clang";
+    });
 
 in rec {
-  inherit toolchain;
+  toolchain = toolchain pkgs;
 
   devShell = pkgs.mkShell {
     buildInputs = [