Auto merge of #39086 - aidanhs:aphs-local-rebuild-no-jemalloc, r=alexcrichton

Make rustbuild force_alloc_system rather than relying on stage0

This 'fixes' jemalloc-less local rebuilds, where we tell cargo that we're actually stage1 (this only fixes the rustbuild path, since I wasn't enthusiastic to dive into the makefiles).

There should be one effect from this PR: `--enable-local-rebuild --disable-jemalloc` will successfully build a stage0 std (rather than erroring). Ideally I think it'd be nice to specify an allocator preference in Cargo.toml/cargo command line (used when an allocator must be picked i.e. dylibs, not rlibs), but since that's not possible we can make do with a force_alloc_system feature. Sadly this locks you into a single allocator in the build libstd, making any eventual implementation of #38575 not quite right in this edge case, but clearly not many people exercise the combination of these two flags.

This PR is also a substitute for #37975 I think. The crucial difference is that the feature name here is distinct from the jemalloc feature (reused in the previous PR) - we don't want someone to be forced into alloc_system just for disabling jemalloc!

Fixes #39054

r? @alexcrichton

1 files changed, 10 insertions, 1 deletions

diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 079f93e7331..7bc11d88eba 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -42,7 +42,16 @@ pub fn std(build: &Build, target: &str, compiler: &Compiler) {
     let out_dir = build.cargo_out(compiler, Mode::Libstd, target);
     build.clear_if_dirty(&out_dir, &build.compiler_path(compiler));
     let mut cargo = build.cargo(compiler, Mode::Libstd, target, "build");
-    cargo.arg("--features").arg(build.std_features())
+    let mut features = build.std_features();
+    // When doing a local rebuild we tell cargo that we're stage1 rather than
+    // stage0. This works fine if the local rust and being-built rust have the
+    // same view of what the default allocator is, but fails otherwise. Since
+    // we don't have a way to express an allocator preference yet, work
+    // around the issue in the case of a local rebuild with jemalloc disabled.
+    if compiler.stage == 0 && build.local_rebuild && !build.config.use_jemalloc {
+        features.push_str(" force_alloc_system");
+    }
+    cargo.arg("--features").arg(features)
          .arg("--manifest-path")
          .arg(build.src.join("src/rustc/std_shim/Cargo.toml"));