[WIP] per profile sysroot via Cargo.toml

src/cargo/core/manifest.rs

@@ -113,6 +113,7 @@ pub struct Profile {
     pub test: bool,
     pub doc: bool,
     pub run_custom_build: bool,
+    pub sysroot: Option<PathBuf>,
 }
 
 #[derive(Default, Clone, Debug)]
@@ -466,6 +467,7 @@ impl Default for Profile {
             test: false,
             doc: false,
             run_custom_build: false,
+            sysroot: None,
         }
     }
 }

src/cargo/ops/cargo_rustc/mod.rs

@@ -3,7 +3,7 @@ use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fs;
 use std::io::prelude::*;
-use std::path::{self, PathBuf};
+use std::path::{self, Path, PathBuf};
 use std::sync::Arc;
 
 use core::{Package, PackageId, PackageSet, Target, Resolve};
@@ -446,10 +446,32 @@ fn build_base_args(cx: &Context,
                    cmd: &mut CommandPrototype,
                    unit: &Unit,
                    crate_types: &[&str]) {
+    // Check if the sysroot is applicable for this Unit
+    // For the explanation of this logic see Context::rustflags_args
+    fn applicable_sysroot<'a>(sysroot: &'a Option<PathBuf>,
+                         cx: &Context,
+                         unit: &Unit) -> Option<&'a Path> {
+        sysroot.as_ref().and_then(|sysroot| {
+            let compiling_with_target = cx.build_config.requested_target.is_some();
+            let is_target_kind = unit.kind == Kind::Target;
+            let use_sysroot = match (compiling_with_target, is_target_kind) {
+                (false, _) => true,
+                (true, true) => true,
+                (true, false) => false,
+            };
+
+            if use_sysroot {
+                Some(&**sysroot)
+            } else {
+                None
+            }
+        })
+    }
+
     let Profile {
         opt_level, lto, codegen_units, ref rustc_args, debuginfo,
         debug_assertions, rpath, test, doc: _doc, run_custom_build,
-        rustdoc_args: _,
+        ref sysroot, rustdoc_args: _,
     } = *unit.profile;
     assert!(!run_custom_build);
 
@@ -458,6 +480,10 @@ fn build_base_args(cx: &Context,
 
     cmd.arg(&root_path(cx, unit));
 
+    if let Some(sysroot) = applicable_sysroot(sysroot, cx, unit) {
+        cmd.arg("--sysroot").arg(sysroot.display().to_string());
+    }
+
     cmd.arg("--crate-name").arg(&unit.target.crate_name());
 
     for crate_type in crate_types.iter() {

src/cargo/util/toml.rs

@@ -243,6 +243,7 @@ pub struct TomlProfile {
     debug: Option<bool>,
     debug_assertions: Option<bool>,
     rpath: Option<bool>,
+    sysroot: Option<String>,
 }
 
 #[derive(RustcDecodable)]
@@ -973,7 +974,7 @@ fn build_profiles(profiles: &Option<TomlProfiles>) -> Profiles {
 
     fn merge(profile: Profile, toml: Option<&TomlProfile>) -> Profile {
         let &TomlProfile {
-            opt_level, lto, codegen_units, debug, debug_assertions, rpath
+            opt_level, lto, codegen_units, debug, debug_assertions, rpath, ref sysroot
         } = match toml {
             Some(toml) => toml,
             None => return profile,
@@ -990,6 +991,9 @@ fn build_profiles(profiles: &Option<TomlProfiles>) -> Profiles {
             test: profile.test,
             doc: profile.doc,
             run_custom_build: profile.run_custom_build,
+            // FIXME if 'sysroot' is a relative path it should be relative to the root of the cargo
+            // project (???)
+            sysroot: sysroot.as_ref().map(|s| PathBuf::from(s)),
         }
     }
 }