rust: Clean up target configs and test some more

See the new docs for details. The difference is vis-a-vis older versions
of this PR, not master.

1 files changed, 37 insertions, 23 deletions

diff --git a/pkgs/test/rust-sysroot/default.nix b/pkgs/test/rust-sysroot/default.nix
index cd07ef53c32d..3a786ad6f00b 100644
--- a/pkgs/test/rust-sysroot/default.nix
+++ b/pkgs/test/rust-sysroot/default.nix
@@ -1,6 +1,7 @@
-{ lib, rustPlatform, fetchFromGitHub, writeText }:
+{ lib, rust, rustPlatform, fetchFromGitHub }:
 
-rustPlatform.buildRustPackage rec {
+let
+  mkBlogOsTest = target: rustPlatform.buildRustPackage rec {
     name = "blog_os-sysroot-test";
 
     src = fetchFromGitHub {
@@ -12,27 +13,7 @@ rustPlatform.buildRustPackage rec {
 
     cargoSha256 = "1cbcplgz28yxshyrp2krp1jphbrcqdw6wxx3rry91p7hiqyibd30";
 
-    # The book uses rust-lld for linking, but rust-lld is not currently packaged for NixOS.
-    # The justification in the book for using rust-lld suggests that gcc can still be used for testing:
-    # > Instead of using the platform's default linker (which might not support Linux targets),
-    # > we use the cross platform LLD linker that is shipped with Rust for linking our kernel.
-    # https://github.com/phil-opp/blog_os/blame/7212ffaa8383122b1eb07fe1854814f99d2e1af4/blog/content/second-edition/posts/02-minimal-rust-kernel/index.md#L157
-    target = writeText "x86_64-blog_os.json" ''
-        {
-            "llvm-target": "x86_64-unknown-none",
-            "data-layout": "e-m:e-i64:64-f80:128-n8:16:32:64-S128",
-            "arch": "x86_64",
-            "target-endian": "little",
-            "target-pointer-width": "64",
-            "target-c-int-width": "32",
-            "os": "none",
-            "executables": true,
-            "linker-flavor": "gcc",
-            "panic-strategy": "abort",
-            "disable-redzone": true,
-            "features": "-mmx,-sse,+soft-float"
-        }
-    '';
+    inherit target;
 
     RUSTFLAGS = "-C link-arg=-nostartfiles";
 
@@ -42,5 +23,38 @@ rustPlatform.buildRustPackage rec {
     meta = with lib; {
         description = "Test for using custom sysroots with buildRustPackage";
         maintainers = with maintainers; [ aaronjanse ];
+        platforms = lib.platforms.x86_64;
     };
+  };
+
+  # The book uses rust-lld for linking, but rust-lld is not currently packaged for NixOS.
+  # The justification in the book for using rust-lld suggests that gcc can still be used for testing:
+  # > Instead of using the platform's default linker (which might not support Linux targets),
+  # > we use the cross platform LLD linker that is shipped with Rust for linking our kernel.
+  # https://github.com/phil-opp/blog_os/blame/7212ffaa8383122b1eb07fe1854814f99d2e1af4/blog/content/second-edition/posts/02-minimal-rust-kernel/index.md#L157
+  targetContents = {
+    "llvm-target" = "x86_64-unknown-none";
+    "data-layout" = "e-m:e-i64:64-f80:128-n8:16:32:64-S128";
+    "arch" = "x86_64";
+    "target-endian" = "little";
+    "target-pointer-width" = "64";
+    "target-c-int-width" = "32";
+    "os" = "none";
+    "executables" = true;
+    "linker-flavor" = "gcc";
+    "panic-strategy" = "abort";
+    "disable-redzone" = true;
+    "features" = "-mmx,-sse,+soft-float";
+  };
+
+in {
+  blogOS-targetByFile = mkBlogOsTest (builtins.toFile "x86_64-blog_os.json" (builtins.toJSON targetContents));
+  blogOS-targetByNix = let
+    plat = lib.systems.elaborate { config = "x86_64-none"; } // {
+      rustc = {
+        config = "x86_64-blog_os";
+        platform = targetContents;
+      };
+    };
+    in mkBlogOsTest (rust.toRustTargetSpec plat);
 }