path: root/0002-Remove-the-prebuilt-toolchain-from-the-Android-team.patch

From 635f82e7dd5802b338a5a404f92672b1ed878df1 Mon Sep 17 00:00:00 2001
From: danakj <danakj@chromium.org>
Date: Thu, 4 May 2023 16:33:48 +0000
Subject: [PATCH] Remove the prebuilt toolchain from the Android team

We build our own compiler and stdlib for Chrome unconditionally now, so
this is no longer used.

These paths were broken while fixing the Windows build, so time for
them to go.

Bug: 1292038
Change-Id: I9d43875671245e5be08fa63aff06f13c0b2243d9
Cq-Include-Trybots: luci.chromium.try:android-rust-arm32-rel,android-rust-arm64-dbg,android-rust-arm64-rel,linux-rust-x64-rel,linux-rust-x64-dbg,win-rust-x64-rel,win-rust-x64-dbg
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4500460
Reviewed-by: Adrian Taylor <adetaylor@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1139597}
---
 DEPS                                          | 13 ----
 build/config/rust.gni                         | 75 +++++++------------
 build/rust/std/BUILD.gn                       | 57 ++++----------
 build/rust/std/find_std_rlibs.py              | 32 --------
 .../ci/android-rust-arm32-rel/properties.json |  3 +-
 .../ci/android-rust-arm64-dbg/properties.json |  3 +-
 .../ci/android-rust-arm64-rel/properties.json |  3 +-
 .../android-rust-arm32-rel/properties.json    |  3 +-
 .../android-rust-arm64-dbg/properties.json    |  3 +-
 .../android-rust-arm64-rel/properties.json    |  3 +-
 .../chromium/ci/chromium.rust.star            |  3 -
 11 files changed, 47 insertions(+), 151 deletions(-)

diff --git a/DEPS b/DEPS
index 98d20c55e07a5..9606cafe4c800 100644
--- a/DEPS
+++ b/DEPS
@@ -241,9 +241,6 @@ vars = {
   # Fetch Rust toolchain.
   'checkout_rust': 'host_os == "linux"',
 
-  # Fetch the Android team's Rust toolchain.
-  'fetch_android_chromium_rust_toolchain': False,
-
   # See //docs/testing/regression-test-selection.md
   # for info on RTS
   'checkout_rts_model': False,
@@ -560,16 +557,6 @@ deps = {
     ],
     'dep_type': 'cipd',
   },
-  'src/third_party/android_rust_toolchain/toolchain': {
-    'packages': [
-      {
-        'package': 'chromium/third_party/android_rust_toolchain/linux-amd64',
-        'version': 'version:2@1.64.0.cr2',
-      },
-    ],
-    'dep_type': 'cipd',
-    'condition': 'fetch_android_chromium_rust_toolchain',
-  },
 
   # We don't know target_cpu at deps time. At least until there's a universal
   # binary of httpd-php, pull both intel and arm versions in DEPS and then pick
diff --git a/build/config/rust.gni b/build/config/rust.gni
index c0d934ce193f2..544ca33a8e036 100644
--- a/build/config/rust.gni
+++ b/build/config/rust.gni
@@ -35,19 +35,18 @@ declare_args() {
   # all Rust features enabled.
   enable_all_rust_features = false
 
-  # Use the Rust toolchain built in-tree. See //tools/rust.
-  use_chromium_rust_toolchain = true
-
-  # Chromium currently has a Rust toolchain for Android and Linux, but
-  # if you wish to experiment on more platforms you can use this
-  # argument to specify an alternative toolchain.
-  # This should be an absolute path to a directory
-  # containing a 'bin' directory and others. Commonly
+  # Chromium provides a Rust toolchain in //third_party/rust-toolchain when
+  # checkout_rust is True (which is being rolled out by default over time).
+  #
+  # To use a custom toolchain instead, specify an absolute path to the root of
+  # a Rust sysroot, which will have a 'bin' directory and others. Commonly
   # <home dir>/.rustup/toolchains/nightly-<something>-<something>
   rust_sysroot_absolute = ""
 
-  # If you're using an external Rust toolchain, set this to a Rust
-  # the output of rustc -V.
+  # If you're using a Rust toolchain as specified by rust_sysroot_absolute,
+  # set this to the output of `rustc -V`. Changing this string will cause all
+  # Rust targets to be rebuilt, which allows you to update your toolchain and
+  # not break incremental builds.
   rustc_version = ""
 
   # If you're using a Rust toolchain as specified by rust_sysroot_absolute,
@@ -77,10 +76,9 @@ declare_args() {
   host_toolchain_no_sanitizers = host_toolchain
 }
 
+# Use a separate declare_args so these variables' defaults can depend on the
+# ones above.
 declare_args() {
-  # Use a separate declare_args so these variables' defaults can depend on the
-  # ones above.
-
   # Individual Rust components.
 
   # Conversions between Rust types and C++ types.
@@ -105,36 +103,33 @@ declare_args() {
   enable_rust_boringssl = enable_all_rust_features
 }
 
-# Platform support for "official" toolchains (Android or Chromium)
-android_toolchain_supports_platform =
-    (!is_nacl &&
-     (is_android && (current_cpu == "arm" || current_cpu == "arm64" ||
-                     current_cpu == "x64" || current_cpu == "x86"))) ||
-    (is_linux && current_cpu == "x64")
+# Use the Rust toolchain built in-tree. When false, we use the prebuilt Rust
+# stdlibs that come with the specified custom toolchain.
+use_chromium_rust_toolchain = rust_sysroot_absolute == ""
+
+# Platform support for the Rust toolchain.
 chromium_toolchain_supports_platform = !is_nacl
 custom_toolchain_supports_platform = !is_nacl || rust_toolchain_supports_nacl
 
-toolchain_has_rust =
-    enable_rust &&
-    ((use_chromium_rust_toolchain && chromium_toolchain_supports_platform) ||
-     (!use_chromium_rust_toolchain && android_toolchain_supports_platform) ||
-     (rust_sysroot_absolute != "" && custom_toolchain_supports_platform))
+# Not all target triples (GN toolchains) are supported by the Rust compiler.
+# Define if we support the current GN toolchain.
+toolchain_has_rust = false
 
 # The rustc_revision is used to introduce a dependency on the toolchain version
 # (so e.g. rust targets are rebuilt, and the standard library is re-copied when
 # the toolchain changes). It is left empty for custom toolchains.
 rustc_revision = ""
-if (toolchain_has_rust) {
+
+if (enable_rust) {
   if (use_chromium_rust_toolchain) {
+    toolchain_has_rust = chromium_toolchain_supports_platform
     update_rust_args = [ "--print-package-version" ]
     rustc_revision = exec_script("//tools/rust/update_rust.py",
                                  update_rust_args,
                                  "trim string")
-  } else if (rust_sysroot_absolute != "") {
-    rustc_revision = rustc_version
   } else {
-    # Android toolchain version.
-    rustc_revision = "rustc 1.64.0-dev (Android Rust Toolchain version 9099361)"
+    toolchain_has_rust = custom_toolchain_supports_platform
+    rustc_revision = rustc_version
   }
 }
 
@@ -150,21 +145,10 @@ build_rust_crash = toolchain_has_rust && enable_rust_crash
 # portability. In practice if an external toolchain was specified, it might
 # be an absolute path, but we'll do our best.
 if (enable_rust) {
-  if (rust_sysroot_absolute != "") {
-    rust_sysroot = get_path_info(rust_sysroot_absolute, "abspath")
-    use_unverified_rust_toolchain = true
-  } else if (use_chromium_rust_toolchain) {
+  if (use_chromium_rust_toolchain) {
     rust_sysroot = "//third_party/rust-toolchain"
-    use_unverified_rust_toolchain = false
   } else {
-    if (host_os != "linux") {
-      assert(false,
-             "Attempt to use Android Rust toolchain on an unsupported platform")
-    }
-
-    rust_sysroot = "//third_party/android_rust_toolchain/toolchain"
-    use_unverified_rust_toolchain = false
-    extra_sysroot_libs += [ "libunwind.a" ]
+    rust_sysroot = get_path_info(rust_sysroot_absolute, "abspath")
   }
 }
 
@@ -266,13 +250,6 @@ if (current_cpu == "x86") {
 
 assert(!toolchain_has_rust || rust_target_arch != "")
 
-# Must use Chromium Rust toolchain to get precisely matching LLVM versions
-# in order to enable LTO. Some say that LTO probably works if LLVM is "close
-# enough", but we don't want to take that risk.
-assert(!use_thin_lto || !enable_rust || use_chromium_rust_toolchain ||
-           use_unverified_rust_toolchain,
-       "Must use Chromium Rust toolchain for LTO")
-
 # Arguments for Rust invocation.
 # This is common between gcc/clang, Mac and Windows toolchains so specify once,
 # here. This is not the complete command-line: toolchains should add -o
diff --git a/build/rust/std/BUILD.gn b/build/rust/std/BUILD.gn
index 03b894327c0d0..60aea480a42a1 100644
--- a/build/rust/std/BUILD.gn
+++ b/build/rust/std/BUILD.gn
@@ -70,12 +70,6 @@ if (toolchain_has_rust) {
     "unwind",
   ]
 
-  # rlibs explicitly ignored when copying prebuilt sysroot libraries.
-  # find_std_rlibs.py rightfully errors out if an unexpected prebuilt lib is
-  # encountered, since it usually indicates we missed something. This ignore
-  # list is also passed to it. This has no effect on the local std build.
-  ignore_stdlib_files = []
-
   # proc_macro is special: we only run proc macros on the host, so we only want
   # it for our host toolchain.
   if (current_toolchain == host_toolchain_no_sanitizers) {
@@ -83,10 +77,6 @@ if (toolchain_has_rust) {
     # includes proc_macro in the prebuilts copied in find_stdlib. Otherwise it
     # is not built or copied.
     stdlib_files += [ "proc_macro" ]
-  } else {
-    # Explicitly ignore it from the prebuilts. Nothing needs to be done for the
-    # local std build.
-    ignore_stdlib_files += [ "proc_macro" ]
   }
 
   # Different Rust toolchains may add or remove files relative to the above
@@ -198,9 +188,11 @@ if (toolchain_has_rust) {
     }
 
     group("local_stdlib_libs") {
-      assert(
-          enable_rust,
-          "Some C++ target is including Rust code even though enable_rust=false")
+      assert(toolchain_has_rust,
+             "Some C++ target is depending on Rust code even though " +
+                 "toolchain_has_rust=false. Usually this would mean" +
+                 "a NaCl target is depending on Rust, as there's no Rust " +
+                 "toolchain targetting NaCl.")
       all_dependent_configs = [ ":stdlib_dependent_libs" ]
       deps = []
       foreach(libname, stdlib_files + skip_stdlib_files) {
@@ -212,9 +204,6 @@ if (toolchain_has_rust) {
     # Builds the stdlib and points the rustc `--sysroot` to them. Used by
     # targets for which linking is driven by Rust (bins and dylibs).
     group("stdlib_for_rustc") {
-      assert(
-          enable_rust,
-          "Some C++ target is including Rust code even though enable_rust=false")
       all_dependent_configs = [ ":local_stdlib_sysroot" ]
       public_deps = [ ":local_stdlib_libs" ]
     }
@@ -228,27 +217,25 @@ if (toolchain_has_rust) {
         ":remap_alloc",
       ]
     }
-
-    not_needed([ "ignore_stdlib_files" ])
   } else {
     action("find_stdlib") {
-      # Collect prebuilt Rust libraries from toolchain package and copy to a known
-      # location.
+      # Collect prebuilt Rust libraries from toolchain package and copy to a
+      # known location.
       #
       # The Rust toolchain contains prebuilt rlibs for the standard library and
       # its dependencies. However, they have unstable names: an unpredictable
       # metadata hash is appended to the known crate name.
       #
       # We must depend on these rlibs explicitly when rustc is not in charge of
-      # linking. However, it is difficult to construct GN rules to do so when the
-      # names can't be known statically.
+      # linking. However, it is difficult to construct GN rules to do so when
+      # the names can't be known statically.
       #
       # This action copies the prebuilt rlibs to a known location, removing the
       # metadata part of the name. In the process it verifies we have all the
-      # libraries we expect and none that we don't. A depfile is generated so this
-      # step is re-run when any libraries change. The action script additionally
-      # verifies rustc matches the expected version, which is unrelated but this
-      # is a convenient place to do so.
+      # libraries we expect and none that we don't. A depfile is generated so
+      # this step is re-run when any libraries change. The action script
+      # additionally verifies rustc matches the expected version, which is
+      # unrelated but this is a convenient place to do so.
       #
       # The action refers to `stdlib_files`, `skip_stdlib_files`, and the
       # associated //build/config/rust.gni vars `removed_rust_stdlib_libs` and
@@ -259,8 +246,8 @@ if (toolchain_has_rust) {
       out_libdir = rebase_path(target_out_dir, root_build_dir)
       out_depfile = rebase_path(depfile, root_build_dir)
 
-      # For the rustc sysroot we must include even the rlibs we don't pass to the
-      # C++ linker.
+      # For the rustc sysroot we must include even the rlibs we don't pass to
+      # the C++ linker.
       all_stdlibs_to_copy = stdlib_files + skip_stdlib_files
       args = [
         "--rust-bin-dir",
@@ -282,20 +269,6 @@ if (toolchain_has_rust) {
         rustc_revision,
       ]
 
-      if (!use_unverified_rust_toolchain) {
-        args += [
-          "--stdlibs",
-          string_join(",", all_stdlibs_to_copy),
-        ]
-
-        if (ignore_stdlib_files != []) {
-          args += [
-            "--ignore-stdlibs",
-            string_join(",", ignore_stdlib_files),
-          ]
-        }
-      }
-
       if (extra_sysroot_libs != []) {
         args += [
           "--extra-libs",
diff --git a/build/rust/std/find_std_rlibs.py b/build/rust/std/find_std_rlibs.py
index 85ab477a9450c..386258f890c01 100755
--- a/build/rust/std/find_std_rlibs.py
+++ b/build/rust/std/find_std_rlibs.py
@@ -33,10 +33,6 @@ def main():
   parser.add_argument("--depfile-target",
                       help="Target to key depfile around",
                       required=True)
-  parser.add_argument("--stdlibs",
-                      help="Expected list of standard library libraries")
-  parser.add_argument("--ignore-stdlibs",
-                      help="List of sysroot libraries to ignore")
   parser.add_argument("--extra-libs",
                       help="List of extra non-libstd sysroot libraries")
   parser.add_argument("--rustc-revision",
@@ -44,24 +40,6 @@ def main():
                       " on the rustc version.")
   args = parser.parse_args()
 
-  # Expected rlibs by concise name (the crate name, plus a disambiguating suffix
-  # e.g. "-2" when necessary).
-  if args.stdlibs:
-    rlibs_expected = set()
-    for lib in args.stdlibs.split(','):
-      # The version is only included if there's more than one of `name`, and
-      # even then is only included for the 2nd onward.
-      (name, version) = EXPECTED_STDLIB_INPUT_REGEX.match(lib).group(1, 2)
-      if version is None:
-        rlibs_expected.add(name)
-      else:
-        rlibs_expected.add(f"{name}-{version}")
-    ignore_rlibs = set()
-    if args.ignore_stdlibs is not None:
-      ignore_rlibs = set(args.ignore_stdlibs.split(','))
-  else:
-    rlibs_expected = None
-
   extra_libs = set()
   if args.extra_libs:
     for lib in args.extra_libs.split(','):
@@ -138,13 +116,6 @@ def copy_file(infile, outfile):
 
       output_filename = f"lib{concise_name}.rlib"
 
-      if rlibs_expected is not None:
-        if concise_name in ignore_rlibs:
-          continue
-        if concise_name not in rlibs_expected:
-          raise Exception("Found stdlib rlib that wasn't expected: %s" % f)
-        rlibs_expected.remove(concise_name)
-
       infile = os.path.join(rustlib_dir, f)
       outfile = os.path.join(args.output, output_filename)
       copy_file(infile, outfile)
@@ -155,9 +126,6 @@ def copy_file(infile, outfile):
       copy_file(infile, outfile)
 
     depfile.write("\n")
-    if rlibs_expected:
-      raise Exception("We failed to find all expected stdlib rlibs: %s" %
-                      ','.join(rlibs_expected))
 
 
 if __name__ == '__main__':