Auto merge of #43589 - aidanhs:aphs-fix-system-malloc, r=alexcrichton

Make a disable-jemalloc build work

Fixes #43510. I've tested this up to building a stage1 compiler.

r? @alexcrichton

cc @cuviper @vorner

@cuviper your fix was almost correct, you just had a stray `!` in there which caused the second error you saw.

src/librustc_trans/back/symbol_export.rs

@@ -13,6 +13,7 @@ use rustc::util::nodemap::{FxHashMap, NodeSet};
 use rustc::hir::def_id::{DefId, CrateNum, LOCAL_CRATE, INVALID_CRATE, CRATE_DEF_INDEX};
 use rustc::session::config;
 use rustc::ty::TyCtxt;
+use rustc_allocator::ALLOCATOR_METHODS;
 use syntax::attr;
 
 /// The SymbolExportLevel of a symbols specifies from which kinds of crates
@@ -83,6 +84,14 @@ impl ExportedSymbols {
                               SymbolExportLevel::C));
         }
 
+        if tcx.sess.allocator_kind.get().is_some() {
+            for method in ALLOCATOR_METHODS {
+                local_crate.push((format!("__rust_{}", method.name),
+                                  INVALID_DEF_ID,
+                                  SymbolExportLevel::Rust));
+            }
+        }
+
         if let Some(id) = tcx.sess.derive_registrar_fn.get() {
             let def_id = tcx.hir.local_def_id(id);
             let idx = def_id.index;

src/libstd/lib.rs

@@ -318,6 +318,22 @@
 
 #![default_lib_allocator]
 
+// Always use alloc_system during stage0 since we don't know if the alloc_*
+// crate the stage0 compiler will pick by default is enabled (e.g.
+// if the user has disabled jemalloc in `./configure`).
+// `force_alloc_system` is *only* intended as a workaround for local rebuilds
+// with a rustc without jemalloc.
+// The not(stage0+msvc) gates will only last until the next stage0 bump
+#![cfg_attr(all(
+        not(all(stage0, target_env = "msvc")),
+        any(stage0, feature = "force_alloc_system")),
+    feature(global_allocator))]
+#[cfg(all(
+    not(all(stage0, target_env = "msvc")),
+    any(stage0, feature = "force_alloc_system")))]
+#[global_allocator]
+static ALLOC: alloc_system::System = alloc_system::System;
+
 // Explicitly import the prelude. The compiler uses this same unstable attribute
 // to import the prelude implicitly when building crates that depend on std.
 #[prelude_import]

src/tools/tidy/src/pal.rs

@@ -69,6 +69,7 @@ const EXCEPTION_PATHS: &'static [&'static str] = &[
     "src/libstd/path.rs",
     "src/libstd/f32.rs",
     "src/libstd/f64.rs",
+    "src/libstd/lib.rs", // Until next stage0 snapshot bump
     "src/libstd/sys_common/mod.rs",
     "src/libstd/sys_common/net.rs",
     "src/libterm", // Not sure how to make this crate portable, but test needs it