Build rustc from source, fix a few issues with the RTS build system

default.nix

@@ -18,17 +18,83 @@ let ic-ref = ic-ref-pkgs.ic-ref; in
 let haskellPackages = nixpkgs.haskellPackages.override {
       overrides = import nix/haskell-packages.nix nixpkgs subpath;
     }; in
+
+let
+  rustc-custom = stdenv.mkDerivation rec {
+    name = "rustc-custom";
+    rev = "e327a823d8b64e294e490efeca7829f383aa119d";
+    src = nixpkgs.fetchgit {
+      url = "https://github.com/rust-lang/rust";
+      rev = "e327a823d8b64e294e490efeca7829f383aa119d";
+      sha256 = "1jw64zdf0ikvgnxn72rpbl548s5wzgbc47sx920944872651b7bl";
+    };
+
+    buildInputs = [
+      nixpkgs.llvm_10
+      nixpkgs.python3
+      nixpkgs.curl
+      nixpkgs.cacert
+      nixpkgs.cmake
+      nixpkgs.ninja
+      nixpkgs.libxml2
+      nixpkgs.openssl
+      nixpkgs.pkgconfig
+      # https://github.com/sfackler/rust-openssl/issues/948
+      nixpkgs.libiconv
+    ];
+
+    configurePhase = ''
+      echo -n "Using llvm-config version "
+      ${nixpkgs.llvm_10}/bin/llvm-config --version
+
+      {
+        echo 'changelog-seen = 2'
+
+        echo '[build]'
+        echo 'extended = true'
+        echo 'tools = ["cargo", "src"]'
+
+        echo '[target.x86_64-unknown-linux-gnu]'
+        echo 'llvm-config = "${nixpkgs.llvm_10}/bin/llvm-config"'
+
+        echo '[install]'
+        echo "prefix = \"$out\""
+        echo "sysconfdir = \"$out/etc\""
+      } > config.toml
+
+      echo "config.toml contents:"
+      echo "-------------------------------------------------------------------"
+      cat config.toml
+      echo "-------------------------------------------------------------------"
+    '';
+
+    buildPhase = ''
+      mkdir home
+      export HOME=$PWD/home
+      patchShebangs .
+      ./x.py build
+    '';
+
+    installPhase = ''
+      ./x.py install
+    '';
+  };
+in
+
 let
-  rtsBuildInputs = with nixpkgs; [
-    clang_10 # for native/wasm building
-    lld_10 # for wasm building
-    llvmPackages_10.bintools
-    rustc-nightly
-    cargo-nightly
-    xargo
-    wasmtime
-    rust-bindgen
-    rustfmt
+  rtsBuildInputs = [
+    nixpkgs.clang_10 # for native/wasm building
+    nixpkgs.lld_10 # for wasm building
+    nixpkgs.llvmPackages_10.bintools
+    nixpkgs.wasmtime
+    nixpkgs.rust-bindgen
+
+    rustc-custom
+
+    # For some reason we can't build rustfmt component in the rustc-custom
+    # derivation above (probably a bug in the Rust repo) so we use the one from
+    # nixpkgs
+    nixpkgs.rustfmt
   ];
 
   llvmEnv = ''
@@ -152,7 +218,6 @@ rec {
       buildInputs = rtsBuildInputs;
 
       preBuild = ''
-        export XARGO_HOME=$PWD/xargo-home
         export CARGO_HOME=$PWD/cargo-home
 
         # this replicates logic from nixpkgs’ pkgs/build-support/rust/default.nix
@@ -414,7 +479,6 @@ rec {
   inherit (nixpkgs) wabt wasmtime wasm;
   filecheck = nixpkgs.linkFarm "FileCheck"
     [ { name = "bin/FileCheck"; path = "${nixpkgs.llvm}/bin/FileCheck";} ];
-  inherit (nixpkgs) xargo;
 
   # gitMinimal is used by nix/gitSource.nix; building it here warms the nix cache
   inherit (nixpkgs) gitMinimal;

nix/default.nix

@@ -57,7 +57,6 @@ let
             rustc = rustc-nightly;
             cargo = cargo-nightly;
           };
-          xargo = self.callPackage ./xargo.nix {};
         })
 
 	# wasm-profiler

rts/Makefile

@@ -201,11 +201,11 @@ $(TOMMATH_BINDINGS_RS): | _build
 
 
 $(RTS_RUST_WASM_A): $(TOMMATH_BINDINGS_RS) $(wildcard motoko-rts/src/*.rs) | _build/wasm
-	cd motoko-rts && xargo build --release --target=wasm32-unknown-emscripten
+	cd motoko-rts && cargo build --release --target=wasm32-unknown-emscripten -Z build-std=core
 	cp motoko-rts/target/wasm32-unknown-emscripten/release/libmotoko_rts.a $@
 
 $(RTS_RUST_DEBUG_WASM_A): $(TOMMATH_BINDINGS_RS) $(wildcard motoko-rts/src/*.rs) | _build/wasm
-	cd motoko-rts && xargo build --target=wasm32-unknown-emscripten
+	cd motoko-rts && cargo build --target=wasm32-unknown-emscripten -Z build-std=core
 	cp motoko-rts/target/wasm32-unknown-emscripten/debug/libmotoko_rts.a $@
 
 #
@@ -214,7 +214,7 @@ $(RTS_RUST_DEBUG_WASM_A): $(TOMMATH_BINDINGS_RS) $(wildcard motoko-rts/src/*.rs)
 
 .PHONY: test
 test: $(TOMMATH_WASM_A) $(TOMMATH_BINDINGS_RS)
-	cd motoko-rts-tests && cargo build --target=wasm32-wasi
+	cd motoko-rts-tests && cargo build --target=wasm32-wasi -Z build-std=core
 	wasmtime --disable-cache --cranelift motoko-rts-tests/target/wasm32-wasi/debug/motoko-rts-tests.wasm
 
 #
@@ -259,5 +259,4 @@ clean:
 	  mo-rts-debug.wasm \
 	  motoko-rts/target \
 	  motoko-rts-tests/target \
-	  motoko-rts/xargo-home \
 	  motoko-rts/cargo-home

rts/README.md

@@ -58,7 +58,7 @@ See `motoko-rts/src/bigint.rs` for the technical details.
 Rust build
 ----------
 
-The Rust parts are built from `motoko-rts`, using `xargo` and `cargo`.
+The Rust parts are built from `motoko-rts`, using `cargo`.
 
 To build this in nix, we need pre-fetch some dependencies (currently
 `compiler_builtins` and `libc`). This works in `nix-build` by:

rts/motoko-rts/Cargo.toml

@@ -22,20 +22,6 @@ panic_handler = []
 [dependencies]
 libc = { version = "0.2.81", default_features = false }
 
-# Added here so that it ends up in Cargo.lock, so that nix will pre-fetch it
-[dependencies.compiler_builtins]
-version = "0.1.39"
-# Without this feature we get dozens of duplicate symbol errors when generating
-# the final shared .wasm file:
-#
-#     wasm-ld: error: duplicate symbol: __multi3
-#     >>> defined in _build/wasm/libmotoko_rts.a(compiler_builtins-d709bd899857aa61.compiler_builtins.3abndchk-cgu.0.rcgu.o)
-#     >>> defined in _build/wasm/libmotoko_rts.a(compiler_builtins-06d1ead628e1f468.compiler_builtins.6moz1ltd-cgu.0.rcgu.o)
-#
-# It seems like we're linking multiple versions of compiler_builtins in the same
-# shared library, which we should fix at some point. TODO
-features = ["mangled-names"]
-
 [profile.dev]
 panic = "abort"
 

rts/motoko-rts/native/Cargo.toml

@@ -11,10 +11,6 @@ path = "../src/lib.rs"
 [dependencies]
 libc = { version = "0.2.73", default_features = false }
 
-[dependencies.compiler_builtins]
-version = "0.1.39"
-features = ["mangled-names"]
-
 [profile.dev]
 panic = "abort"