From 92669f8e219037dff5bd1929fd658ed3843f2097 Mon Sep 17 00:00:00 2001
From: Julius Michaelis <gitter@liftm.de>
Date: Thu, 13 Jun 2024 22:44:59 +0900
Subject: [PATCH] rustc: set up sysroot for wasm32-wasi and fix build

---
 lib/systems/examples.nix                        | 1 +
 pkgs/development/compilers/rust/rustc.nix       | 4 +++-
 pkgs/development/libraries/wasilibc/default.nix | 6 ++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/systems/examples.nix b/lib/systems/examples.nix
index 178536efb0091..ba85060d53b48 100644
--- a/lib/systems/examples.nix
+++ b/lib/systems/examples.nix
@@ -353,6 +353,7 @@ rec {
 
   wasi32 = {
     config = "wasm32-unknown-wasi";
+    rustc.config = "wasm32-wasip1";
     useLLVM = true;
   };
 
diff --git a/pkgs/development/compilers/rust/rustc.nix b/pkgs/development/compilers/rust/rustc.nix
index a68e117658fad..656038da4e80b 100644
--- a/pkgs/development/compilers/rust/rustc.nix
+++ b/pkgs/development/compilers/rust/rustc.nix
@@ -146,7 +146,7 @@ in stdenv.mkDerivation (finalAttrs: {
     # Since fastCross only builds std, it doesn't make sense (and
     # doesn't work) to build a linker.
     "--disable-llvm-bitcode-linker"
-  ] ++ optionals (stdenv.isLinux && !stdenv.targetPlatform.isRedox) [
+  ] ++ optionals (stdenv.isLinux && !stdenv.targetPlatform.isRedox && !stdenv.targetPlatform.isWasi) [
     "--enable-profiler" # build libprofiler_builtins
   ] ++ optionals stdenv.buildPlatform.isMusl [
     "${setBuild}.musl-root=${pkgsBuildBuild.targetPackages.stdenv.cc.libc}"
@@ -154,6 +154,8 @@ in stdenv.mkDerivation (finalAttrs: {
     "${setHost}.musl-root=${pkgsBuildHost.targetPackages.stdenv.cc.libc}"
   ] ++ optionals stdenv.targetPlatform.isMusl [
     "${setTarget}.musl-root=${pkgsBuildTarget.targetPackages.stdenv.cc.libc}"
+  ] ++ optionals stdenv.targetPlatform.isWasi [
+    "${setTarget}.wasi-root=${pkgsBuildTarget.targetPackages.stdenv.cc.libc}"
   ] ++ optionals stdenv.targetPlatform.rust.isNoStdTarget [
     "--disable-docs"
   ] ++ optionals (stdenv.isDarwin && stdenv.isx86_64) [
diff --git a/pkgs/development/libraries/wasilibc/default.nix b/pkgs/development/libraries/wasilibc/default.nix
index c0714a78556a3..d32bd668ff1ef 100644
--- a/pkgs/development/libraries/wasilibc/default.nix
+++ b/pkgs/development/libraries/wasilibc/default.nix
@@ -51,6 +51,12 @@ stdenv.mkDerivation {
 
   preFixup = ''
     ln -s $share/share/undefined-symbols.txt $out/lib/wasi.imports
+    # rustc build expects lib at the path where a make install would put them without the SYSROOT_* overrides
+    TARGET_TRIPLE=wasm32-wasi
+    test -d build/$TARGET_TRIPLE # target triple might change if this is adapted to build p2 or threads, make sure the following doesn't break
+    ln -s $out/lib/ $out/lib/$TARGET_TRIPLE
+    ln -s $dev/include $dev/include/$TARGET_TRIPLE
+    ln -s $share/share $share/share/$TARGET_TRIPLE
   '';
 
   passthru.tests = {