rust: avoid using nightly for sanitizer (ASAN, TSAN).

Use Rust stable for ASAN with RUSTC_BOOTSTRAP environment variable.

RUSTC_BOOTSTRAP is discouraged, but we want to have some stability on
the different compilers that we want to use.

Change-Id: Ia1a9978cb49e1bec5925d3747cf6031637dba069
Priv-Id: fbcda92854c98f4864d32f82b5a8de6197ca729b

Author: nicopauss

build/tests/zcargo.py

@@ -260,8 +260,7 @@ def get_cargo_test_cmd(pkg: str, argv: list[str]) -> list[str]:
         # and
         # https://github.com/rust-lang/wg-cargo-std-aware/issues/29#issuecomment-549950466
         # for panic-abort strategy.
-        cmd.extend(['+nightly', '-Zbuild-std=panic_abort,std',
-                    '-Zpanic-abort-tests'])
+        cmd.extend(['-Zbuild-std=panic_abort,std', '-Zpanic-abort-tests'])
 
     cmd.append('test')
 
@@ -285,6 +284,11 @@ def run_cargo_test_for_pkg(pkg: str, argv: list[str]) -> None:
     env = os.environ.copy()
     env['CARGO_TERM_COLOR'] = 'never'
 
+    if 'USE_SANITIZER' in os.environ:
+        # In order to use unstable features on stable Rust.
+        # See https://doc.rust-lang.org/beta/unstable-book/compiler-environment-variables/RUSTC_BOOTSTRAP.html#rustc_bootstrap
+        env['RUSTC_BOOTSTRAP'] = '1'
+
     # Use a suppression file to avoid leak in rustlib:
     # https://github.com/rust-lang/rust/issues/151367
     prev_lsan_opts = env.get('LSAN_OPTIONS', '')

build/waftools/rust.py

@@ -291,18 +291,17 @@ def run_cargo(self) -> None:
         ]
 
         # When using a sanitizer, we need to:
-        # - Use nightly with '+nightly' passed before the command.
+        # - Set 'RUSTC_BOOTSTRAP' to use unstable features on stable Rust.
+        #   See https://doc.rust-lang.org/beta/unstable-book/compiler-environment-variables/RUSTC_BOOTSTRAP.html#rustc_bootstrap
         # - Set the environment variable 'RUSTFLAGS' and 'RUSTDOCFLAGS' to
         #   '-Zsanitizer={sanitizer}'.
         # - Build the standard Rust library itself with '-Z build-std'.
         # - Set the explicit target 'x86_64-unknown-linux-gnu'.
         if self.env.USE_SANITIZER and not self.env.USE_PIC:
-            cargo_exec_cmd += [
-                '+nightly',
-            ]
             sanitizer = self.env.SANITIZER
             old_rustflags = os.environ.get('RUSTFLAGS', '')
             old_rustdocflags = os.environ.get('RUSTDOCFLAGS', '')
+            cmd_env['RUSTC_BOOTSTRAP'] = '1'
             cmd_env['RUSTFLAGS'] = f'-Zsanitizer={sanitizer} {old_rustflags}'
             cmd_env['RUSTDOCFLAGS'] = (
                 f'-Zsanitizer={sanitizer} {old_rustdocflags}'
@@ -553,7 +552,6 @@ def sanitizer_add_toolchain(ctx: ConfigurationContext) -> None:
     # '-Zbuild-std=panic_abort,std'.
     ctx.exec_command(ctx.env.RUSTUP + [
         'component', 'add', 'rust-src',
-        '--toolchain', 'nightly-x86_64-unknown-linux-gnu',
     ], stdout=None, stderr=None)