Fix WASI target by getting rid of CC

.github/workflows/ci.yaml

@@ -151,10 +151,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # `wasm32-wasi-stage-final-gcc` is currently broken.
-        # https://github.com/oxalica/rust-overlay/runs/5247844387
-        # example: [cross-aarch64, cross-wasi, cross-mingw]
-        example: [cross-aarch64, cross-mingw]
+        example: [cross-aarch64, cross-wasi, cross-mingw]
 
     steps:
     - name: Checkout

examples/cross-wasi/shell.nix

@@ -7,8 +7,9 @@
   };
   overlays = [ (import ../..) ];
 }).callPackage (
-{ mkShell, stdenv, rust-bin, wasmtime }:
-mkShell {
+# We don't need WASI C compiler from nixpkgs, so use `mkShellNoCC`.
+{ mkShellNoCC, stdenv, rust-bin, wasmtime }:
+mkShellNoCC {
   nativeBuildInputs = [ rust-bin.stable.latest.minimal ];
 
   depsBuildBuild = [ wasmtime ];

mk-aggregated.nix

@@ -1,7 +1,8 @@
-{ lib, stdenv, symlinkJoin, pkgsTargetTarget, bash, gcc }:
+{ lib, stdenv, symlinkJoin, pkgsTargetTarget, bash }:
 { pname, version, components }:
 let
   inherit (lib) optional optionalString;
+  inherit (stdenv) targetPlatform;
 in
 symlinkJoin {
   name = pname + "-" + version;
@@ -15,13 +16,16 @@ symlinkJoin {
   # CC for build script linking.
   # Workaround: should be `pkgsHostHost.cc` but `stdenv`'s cc itself have -1 offset.
   depsHostHostPropagated = [ stdenv.cc ];
+
   # CC for crate linking.
   # Workaround: should be `pkgsHostTarget.cc` but `stdenv`'s cc itself have -1 offset.
-  propagatedBuildInputs = [ pkgsTargetTarget.stdenv.cc ];
+  # N.B. WASM targets don't need our CC.
+  propagatedBuildInputs =
+    optional (!targetPlatform.isWasm) pkgsTargetTarget.stdenv.cc;
 
   # Link dependency for target, required by darwin std.
   depsTargetTargetPropagated =
-    optional (stdenv.targetPlatform.isDarwin) [ pkgsTargetTarget.libiconv ];
+    optional (targetPlatform.isDarwin) [ pkgsTargetTarget.libiconv ];
 
   postBuild = ''
     # If rustc or rustdoc is in the derivation, we need to copy their
@@ -46,9 +50,8 @@ symlinkJoin {
     # symlinkJoin doesn't automatically handle it. Thus do it manually.
     mkdir $out/nix-support
     echo "$depsHostHostPropagated " >$out/nix-support/propagated-host-host-deps
-    echo "$propagatedBuildInputs " >$out/nix-support/propagated-build-inputs
-  '' + optionalString (stdenv.targetPlatform.isDarwin) ''
-    echo "$depsTargetTargetPropagated " >$out/nix-support/propagated-target-target-deps
+    [[ -z "$propagatedBuildInputs" ]] || echo "$propagatedBuildInputs " >$out/nix-support/propagated-build-inputs
+    [[ -z "$depsTargetTargetPropagated" ]] || echo "$depsTargetTargetPropagated " >$out/nix-support/propagated-target-target-deps
   '';
 
   meta.platforms = lib.platforms.all;

mk-component-set.nix

@@ -1,5 +1,5 @@
 # Define component derivations and special treatments.
-{ lib, stdenv, gnutar, autoPatchelfHook, zlib, gccForLibs
+{ lib, stdenv, stdenvNoCC, gnutar, autoPatchelfHook, bintools, zlib, gccForLibs
 , toRustTarget, removeNulls
 }:
 # Release version of the whole set.
@@ -19,7 +19,7 @@ let
     # These components link to `librustc_driver*.so` or `libLLVM*.so`.
     linksToRustc = elem pname [ "clippy-preview" "rls-preview" "miri-preview" "rustc-dev" ];
   in
-    stdenv.mkDerivation rec {
+    stdenvNoCC.mkDerivation rec {
       inherit pname version src;
       name = "${pname}-${version}-${platform}";
 
@@ -31,15 +31,23 @@ let
 
       nativeBuildInputs = [ gnutar ] ++
         # Darwin doesn't use ELF, and they usually just work due to relative RPATH.
-        optional (!dontFixup && !hostPlatform.isDarwin) autoPatchelfHook;
+        optional (!dontFixup && !hostPlatform.isDarwin) autoPatchelfHook ++
+        # For `install_name_tool`.
+        optional (hostPlatform.isDarwin && linksToRustc) bintools;
 
       buildInputs =
         optional (elem pname [ "rustc" "cargo" "llvm-tools-preview" ]) zlib ++
-        # Nightly `rustc` since 2022-02-17 links to `libstdc++.so.6` on Linux.
-        # https://github.com/oxalica/rust-overlay/issues/73
-        optional (!dontFixup && !hostPlatform.isDarwin && pname == "rustc") gccForLibs.lib ++
         optional linksToRustc self.rustc;
 
+      # Nightly `rustc` since 2022-02-17 links to `libstdc++.so.6` on Linux.
+      # https://github.com/oxalica/rust-overlay/issues/73
+      #
+      # N.B. `gcc` is a compiler which is sensitive to `targetPlatform`.
+      # We use `depsHostHost` instead of `buildInputs` to force it ignore the target,
+      # since binaries produced by `rustc` don't actually relies on this gccForLibs.
+      depsHostHost =
+        optional (!dontFixup && !hostPlatform.isDarwin && pname == "rustc") gccForLibs.lib;
+
       dontConfigure = true;
       dontBuild = true;