From 1383290afcbfa2ee88d6c086d383a7f2f17a1f44 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 20 Dec 2018 16:37:25 +0100
Subject: [PATCH] Use the official approach for building liballoc

This means that we don't have to compile core separately. We also don't need to set RUSTFLAGS for building the sysroot, which fixes an issue reported in https://github.com/rust-osdev/cargo-xbuild/commit/5a26976ea0b8271e93bd349cf376d740f53db1b8#r31742585.
---
 src/sysroot.rs | 48 ++++++++++++------------------------------------
 1 file changed, 12 insertions(+), 36 deletions(-)

diff --git a/src/sysroot.rs b/src/sysroot.rs
index 5e8701c..5425f69 100644
--- a/src/sysroot.rs
+++ b/src/sysroot.rs
@@ -44,8 +44,7 @@ fn build(
     let dst = rustlib.parent().join("lib");
     util::mkdir(&dst)?;
 
-    build_libcore(cmode, &ctoml, home, src, &dst, verbose)?;
-    build_liballoc(cmode, &ctoml, home, src, &dst, config, verbose)?;
+    build_liballoc(cmode, &ctoml, src, &dst, config, verbose)?;
 
     // Create hash file
     util::write(&rustlib.parent().join(".hash"), &hash.to_string())?;
@@ -58,7 +57,6 @@ fn build_crate(
     mut stoml: String,
     cmode: &CompilationMode,
     ctoml: &cargo::Toml,
-    home: &Home,
     dst: &Path,
     verbose: bool,
 ) -> Result<()> {
@@ -113,7 +111,6 @@ fn build_crate(
     }
 
     cmd.arg("--");
-    cmd.env("RUSTFLAGS", &format!("--sysroot {}", home.display()));
     cmd.arg("-Z");
     cmd.arg("force-unstable-if-unmarked");
 
@@ -131,39 +128,9 @@ fn build_crate(
     Ok(())
 }
 
-fn build_libcore(
-    cmode: &CompilationMode,
-    ctoml: &cargo::Toml,
-    home: &Home,
-    src: &Src,
-    dst: &Path,
-    verbose: bool,
-) -> Result<()> {
-    const TOML: &'static str = r#"
-[package]
-authors = ["The Rust Project Developers"]
-name = "sysroot"
-version = "0.0.0"
-"#;
-
-    let mut stoml = TOML.to_owned();
-
-    let path = src.path().join("libcore").display().to_string();
-    let mut core_dep = Table::new();
-    core_dep.insert("path".to_owned(), Value::String(path));
-    let mut deps = Table::new();
-    deps.insert("core".to_owned(), Value::Table(core_dep));
-    let mut map = Table::new();
-    map.insert("dependencies".to_owned(), Value::Table(deps));
-    stoml.push_str(&Value::Table(map).to_string());
-
-    build_crate("core", stoml, cmode, ctoml, home, dst, verbose)
-}
-
 fn build_liballoc(
     cmode: &CompilationMode,
     ctoml: &cargo::Toml,
-    home: &Home,
     src: &Src,
     dst: &Path,
     config: &Config,
@@ -182,9 +149,18 @@ version = "0.1.0"
     let mut stoml = TOML.to_owned();
 
     if config.memcpy {
-        stoml.push_str("features = [\"mem\"]\n");
+        stoml.push_str("features = [\"mem\", \"core\"]\n");
+    } else {
+        stoml.push_str("features = [\"rustc-std-workspace-core\"]\n");
     }
 
+    stoml.push_str("[dependencies.core]\n");
+    stoml.push_str(&format!("path = \"{}\"\n", src.path().join("libcore").display()));
+
+    stoml.push_str("[patch.crates-io.rustc-std-workspace-core]\n");
+    stoml.push_str(&format!("path = '{}'\n",
+        src.path().join("tools/rustc-std-workspace-core").display()));
+
     let path = src.path().join("liballoc/lib.rs").display().to_string();
     let mut map = Table::new();
     let mut lib = Table::new();
@@ -193,7 +169,7 @@ version = "0.1.0"
     map.insert("lib".to_owned(), Value::Table(lib));
     stoml.push_str(&Value::Table(map).to_string());
 
-    build_crate("alloc", stoml, cmode, ctoml, home, dst, verbose)
+    build_crate("alloc", stoml, cmode, ctoml, dst, verbose)
 }
 
 fn old_hash(cmode: &CompilationMode, home: &Home) -> Result<Option<u64>> {