From 9ee10432a4b7464f0b068065a278e61ad61d0387 Mon Sep 17 00:00:00 2001
From: Asad Mehmood <asad78611@googlemail.com>
Date: Tue, 7 Jun 2022 11:28:03 +0100
Subject: rust: cargo: Use rustc and cargo built on Build

When cross-compiling a rust package, all we need is the std library compiled
for the target. This uses the final stage compiler which was built for Build
and then uses that as a stage0 compiler for target std library.

It also copies the rust binary from pkgsBuildBuild so that it find the new
lib/rustlib directory.

We also need to create a cargo wrapper which will use the "new" rust compiler

Also makes sure man pages and doc pages are propagated

Co-authored-by: Alyssa Ross <hi@alyssa.is>
Co-authored-by: Sandro <sandro.jaeckel@gmail.com>
Co-authored-by: Rick van Schijndel <Mindavi@users.noreply.github.com>
---
 pkgs/development/compilers/rust/rustc.nix | 44 ++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 4 deletions(-)

(limited to 'pkgs/development/compilers/rust/rustc.nix')

diff --git a/pkgs/development/compilers/rust/rustc.nix b/pkgs/development/compilers/rust/rustc.nix
index 53f7257ecfc58..869dd15df0be9 100644
--- a/pkgs/development/compilers/rust/rustc.nix
+++ b/pkgs/development/compilers/rust/rustc.nix
@@ -15,6 +15,10 @@
 , wezterm
 , firefox
 , thunderbird
+# This only builds std for target and reuses the rustc from build.
+, fastCross
+, lndir
+, makeWrapper
 }:
 
 let
@@ -87,13 +91,13 @@ in stdenv.mkDerivation rec {
     # (build!=target): When cross-building a compiler we need to add
     # the build platform as well so rustc can compile build.rs
     # scripts.
-    ] ++ optionals (stdenv.buildPlatform != stdenv.targetPlatform) [
+    ] ++ optionals (stdenv.buildPlatform != stdenv.targetPlatform && !fastCross) [
       (rust.toRustTargetSpec stdenv.buildPlatform)
 
     # (host!=target): When building a cross-targeting compiler we
     # need to add the host platform as well so rustc can compile
     # build.rs scripts.
-    ] ++ optionals (stdenv.hostPlatform != stdenv.targetPlatform) [
+    ] ++ optionals (stdenv.hostPlatform != stdenv.targetPlatform && !fastCross) [
       (rust.toRustTargetSpec stdenv.hostPlatform)
     ])}"
 
@@ -132,6 +136,37 @@ in stdenv.mkDerivation rec {
     "--set rust.jemalloc"
   ];
 
+  # if we already have a rust compiler for build just compile the target std
+  # library and reuse compiler
+  buildPhase = if fastCross then "
+    runHook preBuild
+
+    mkdir -p build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-{std,rustc}/${rust.toRustTargetSpec stdenv.hostPlatform}/release/
+    ln -s ${rustc}/lib/rustlib/${rust.toRustTargetSpec stdenv.hostPlatform}/libstd-*.so build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-std/${rust.toRustTargetSpec stdenv.hostPlatform}/release/libstd.so
+    ln -s ${rustc}/lib/rustlib/${rust.toRustTargetSpec stdenv.hostPlatform}/librustc_driver-*.so build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-rustc/${rust.toRustTargetSpec stdenv.hostPlatform}/release/librustc.so
+    ln -s ${rustc}/bin/rustc build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-rustc/${rust.toRustTargetSpec stdenv.hostPlatform}/release/rustc-main
+    touch build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-std/${rust.toRustTargetSpec stdenv.hostPlatform}/release/.libstd.stamp
+    touch build/${rust.toRustTargetSpec stdenv.hostPlatform}/stage0-rustc/${rust.toRustTargetSpec stdenv.hostPlatform}/release/.librustc.stamp
+    python ./x.py --keep-stage=0 --stage=1 build library/std
+
+    runHook postBuild
+  " else null;
+
+  installPhase = if fastCross then ''
+    runHook preInstall
+
+    python ./x.py --keep-stage=0 --stage=1 install library/std
+    mkdir -v $out/bin $doc $man
+    makeWrapper ${rustc}/bin/rustc $out/bin/rustc --add-flags "--sysroot $out"
+    makeWrapper ${rustc}/bin/rustdoc $out/bin/rustdoc --add-flags "--sysroot $out"
+    ln -s ${rustc}/lib/rustlib/{manifest-rust-std-,}${rust.toRustTargetSpec stdenv.hostPlatform} $out/lib/rustlib/
+    echo rust-std-${rust.toRustTargetSpec stdenv.hostPlatform} >> $out/lib/rustlib/components
+    lndir ${rustc.doc} $doc
+    lndir ${rustc.man} $man
+
+    runHook postInstall
+  '' else null;
+
   # The bootstrap.py will generated a Makefile that then executes the build.
   # The BOOTSTRAP_ARGS used by this Makefile must include all flags to pass
   # to the bootstrap builder.
@@ -179,7 +214,8 @@ in stdenv.mkDerivation rec {
   nativeBuildInputs = [
     file python3 rustc cmake
     which libffi removeReferencesTo pkg-config xz
-  ];
+  ]
+    ++ optionals fastCross [ lndir makeWrapper ];
 
   buildInputs = [ openssl ]
     ++ optionals stdenv.isDarwin [ libiconv Security ]
@@ -188,7 +224,7 @@ in stdenv.mkDerivation rec {
   outputs = [ "out" "man" "doc" ];
   setOutputFlags = false;
 
-  postInstall = lib.optionalString enableRustcDev ''
+  postInstall = lib.optionalString (enableRustcDev && !fastCross) ''
     # install rustc-dev components. Necessary to build rls, clippy...
     python x.py dist rustc-dev
     tar xf build/dist/rustc-dev*tar.gz
-- 
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