Auto merge of #55660 - alexcrichton:cleanup-alloc-system, r=dtolnay,SimonSapin

Remove the `alloc_system` crate

In what's hopefully one of the final nails in the coffin of the "old allocator story of yore" this PR deletes the `alloc_system` crate and all traces of it from the compiler. The compiler no longer needs to inject allocator crates anywhere and the `alloc_system` crate has no real reason to exist outside the standard library.

The unstable `alloc_system` crate is folded directly into the standard library where its stable interface, the `System` type, remains the same. All unstable traces of `alloc_system` are removed, however.

Author: bors

src/Cargo.lock

@@ -15,16 +15,6 @@ dependencies = [
  "rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
-[[package]]
-name = "alloc_system"
-version = "0.0.0"
-dependencies = [
- "compiler_builtins 0.0.0",
- "core 0.0.0",
- "dlmalloc 0.0.0",
- "libc 0.0.0",
-]
-
 [[package]]
 name = "ammonia"
 version = "1.1.0"
@@ -2104,7 +2094,6 @@ name = "rustc_asan"
 version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
- "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "compiler_builtins 0.0.0",
@@ -2276,7 +2265,6 @@ name = "rustc_lsan"
 version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
- "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "compiler_builtins 0.0.0",
@@ -2328,7 +2316,6 @@ name = "rustc_msan"
 version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
- "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "compiler_builtins 0.0.0",
@@ -2440,7 +2427,6 @@ name = "rustc_tsan"
 version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
- "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "compiler_builtins 0.0.0",
@@ -2679,11 +2665,11 @@ name = "std"
 version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
- "alloc_system 0.0.0",
  "build_helper 0.1.0",
  "cc 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)",
  "compiler_builtins 0.0.0",
  "core 0.0.0",
+ "dlmalloc 0.0.0",
  "libc 0.0.0",
  "panic_abort 0.0.0",
  "panic_unwind 0.0.0",

src/bootstrap/dist.rs

@@ -859,7 +859,6 @@ impl Step for Src {
             "src/build_helper",
             "src/dlmalloc",
             "src/liballoc",
-            "src/liballoc_system",
             "src/libbacktrace",
             "src/libcompiler_builtins",
             "src/libcore",

src/ci/docker/wasm32-unknown/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
   g++ \

src/liballoc/tests/heap.rs

@@ -8,8 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use alloc_system::System;
-use std::alloc::{Global, Alloc, Layout};
+use std::alloc::{Global, Alloc, Layout, System};
 
 /// https://github.com/rust-lang/rust/issues/45955
 #[test]

src/liballoc/tests/lib.rs

@@ -9,7 +9,6 @@
 // except according to those terms.
 
 #![feature(allocator_api)]
-#![feature(alloc_system)]
 #![feature(box_syntax)]
 #![feature(drain_filter)]
 #![feature(exact_size_is_empty)]
@@ -20,7 +19,6 @@
 #![feature(unboxed_closures)]
 #![feature(repeat_generic_slice)]
 
-extern crate alloc_system;
 extern crate core;
 extern crate rand;