From f6b3bcc4313b7d6c217a92f8e9615f0b136c9ab3 Mon Sep 17 00:00:00 2001 From: David Tolnay Date: Sat, 20 Jan 2024 09:47:53 -0800 Subject: [PATCH] Capture the rationale for -Zallow-features= in bootstrap.py --- src/bootstrap/bootstrap.py | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py index 28d96cb1cfe56..83fdcddecf27a 100644 --- a/src/bootstrap/bootstrap.py +++ b/src/bootstrap/bootstrap.py @@ -924,17 +924,29 @@ def build_bootstrap_cmd(self, env): # default toolchain is not nightly. # # But that setting has the collateral effect of rust-analyzer also - # passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various overrideCommand). - # For compiling bootstrap that can cause spurious rebuilding of bootstrap when - # rust-analyzer x.py invocations are interleaved with handwritten ones on the - # command line. + # passing RUSTC_BOOTSTRAP=1 to all x.py invocations too (the various + # overrideCommand). # - # Set RUSTC_BOOTSTRAP=1 consistently. + # Set a consistent RUSTC_BOOTSTRAP=1 here to prevent spurious rebuilds + # of bootstrap when rust-analyzer x.py invocations are interleaved with + # handwritten ones on the command line. env["RUSTC_BOOTSTRAP"] = "1" - default_rustflags = "" if env.get("RUSTFLAGS_BOOTSTRAP", "") else "-Zallow-features=" - - env.setdefault("RUSTFLAGS", default_rustflags) + # If any of RUSTFLAGS or RUSTFLAGS_BOOTSTRAP are present and nonempty, + # we allow arbitrary compiler flags in there, including unstable ones + # such as `-Zthreads=8`. + # + # But if there aren't custom flags being passed to bootstrap, then we + # cancel the RUSTC_BOOTSTRAP=1 from above by passing `-Zallow-features=` + # to ensure unstable language or library features do not accidentally + # get introduced into bootstrap over time. Distros rely on being able to + # compile bootstrap with a variety of their toolchains, not necessarily + # the same as Rust's CI uses. + if env.get("RUSTFLAGS", "") or env.get("RUSTFLAGS_BOOTSTRAP", ""): + # Preserve existing RUSTFLAGS. + env.setdefault("RUSTFLAGS", "") + else: + env["RUSTFLAGS"] = "-Zallow-features=" target_features = [] if self.get_toml("crt-static", build_section) == "true":