Respect RUSTC_LINK_STD_INTO_RUSTC_DRIVER=0 in link_std_into_rustc_driver

[DeepeshWR]

This patch allows users to opt out of statically linking std into rustc_driver by setting the existing environment variable RUSTC_LINK_STD_INTO_RUSTC_DRIVER=0.

• If the variable is unset or set to any other value, the function falls back to the default behavior (linking std on all platforms except Windows).

• Note: This does not introduce a new environment variable; it only respects an existing one.

• Defaults remain unchanged, so normal builds are unaffected.

Example usage:

export RUSTC_LINK_STD_INTO_RUSTC_DRIVER=0
./x.py build

[rustbot]

r? @jieyouxu

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[bjorn3]

This should probably be an option in bootstrap.toml rather than an env var.

Note: This does not introduce a new environment variable; it only respects an existing one.

The existing env var is just an implementation detail of how the main bootstrap executable and the rustc wrapper of bootstrap communicate.

[DeepeshWR]

This should probably be an option in bootstrap.toml rather than an env var.

Note: This does not introduce a new environment variable; it only respects an existing one.

The existing env var is just an implementation detail of how the main bootstrap executable and the rustc wrapper of bootstrap communicate.

Hi @bjorn3,
Thanks for the suggestion.
I’ve updated the patch as follows:

diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index ae91b204062..b444952d16d 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -1125,6 +1125,10 @@ fn run_step_descriptions(&self, v: &[StepDescription], paths: &[PathBuf]) {
     /// Returns if `std` should be statically linked into `rustc_driver`.
     /// It's currently not done on `windows-gnu` due to linker bugs.
     pub fn link_std_into_rustc_driver(&self, target: TargetSelection) -> bool {
+        // Respect bootstrap.toml override if provided
+        if let Some(value) = self.config.link_std_into_rustc_driver {
+            return value;
+        }
         !target.triple.ends_with("-windows-gnu")
     }

diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 17f256188e1..3bd01c0f7b2 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -282,6 +282,7 @@ pub struct Config {
     pub windows_rc: Option<PathBuf>,
     pub reuse: Option<PathBuf>,
     pub cargo_native_static: bool,
+    pub link_std_into_rustc_driver: Option<bool>,
     pub configure_args: Vec<String>,
     pub out: PathBuf,
     pub rust_info: channel::GitInfo,
@@ -485,6 +486,7 @@ pub(crate) fn parse_inner(
             sanitizers: build_sanitizers,
             profiler: build_profiler,
             cargo_native_static: build_cargo_native_static,
+            link_std_into_rustc_driver: build_link_std_into_rustc_driver,
             low_priority: build_low_priority,
             configure_args: build_configure_args,
             local_rebuild: build_local_rebuild,
@@ -1364,6 +1366,7 @@ pub(crate) fn parse_inner(
             libdir: install_libdir.map(PathBuf::from),
             libgccjit_libs_dir: gcc_libgccjit_libs_dir,
             library_docs_private_items: build_library_docs_private_items.unwrap_or(false),
+            link_std_into_rustc_driver: build_link_std_into_rustc_driver,
             lld_enabled,
             lldb: build_lldb.map(PathBuf::from),
             llvm_allow_old_toolchain: llvm_allow_old_toolchain.unwrap_or(false),
diff --git a/src/bootstrap/src/core/config/toml/build.rs b/src/bootstrap/src/core/config/toml/build.rs
index 27bf753f691..042f1216ac7 100644
--- a/src/bootstrap/src/core/config/toml/build.rs
+++ b/src/bootstrap/src/core/config/toml/build.rs
@@ -52,6 +52,7 @@ struct Build {
         sanitizers: Option<bool> = "sanitizers",
         profiler: Option<bool> = "profiler",
         cargo_native_static: Option<bool> = "cargo-native-static",
+        link_std_into_rustc_driver: Option<bool> = "link-std-into-rustc-driver",
         low_priority: Option<bool> = "low-priority",
         configure_args: Option<Vec<String>> = "configure-args",
         local_rebuild: Option<bool> = "local-rebuild",

Is this what you were suggesting ?