add rust.rustflags and per target rustflags options to bootstrap.toml

bootstrap.example.toml

@@ -705,6 +705,12 @@
 # desired in distributions, for example.
 #rust.rpath = true
 
+# Additional flags to pass to `rustc`.
+# Passed before everything else (including per target `rustflags`).
+# Applies to all stages and targets.
+#
+#rust.rustflags = []
+
 # Indicates whether symbols should be stripped using `-Cstrip=symbols`.
 #rust.strip = false
 
@@ -1005,6 +1011,12 @@
 # and will override the same option under [rust] section. It only works on Unix platforms
 #rpath = rust.rpath (bool)
 
+# Additional flags to pass to `rustc`.
+# Passed after global `rust.rustflags` but before everything else.
+# Applies to all stages.
+#
+#rustflags = []
+
 # Force static or dynamic linkage of the standard library for this target. If
 # this target is a host for rustc, this will also affect the linkage of the
 # compiler itself. This is useful for building rustc on targets that normally

src/bootstrap/src/core/builder/cargo.rs

@@ -25,9 +25,7 @@ struct Rustflags(String, TargetSelection);
 
 impl Rustflags {
     fn new(target: TargetSelection) -> Rustflags {
-        let mut ret = Rustflags(String::new(), target);
-        ret.propagate_cargo_env("RUSTFLAGS");
-        ret
+        Rustflags(String::new(), target)
     }
 
     /// By default, cargo will pick up on various variables in the environment. However, bootstrap
@@ -601,6 +599,22 @@ impl Builder<'_> {
         }
 
         let mut rustflags = Rustflags::new(target);
+
+        for arg in &self.config.rust_rustflags {
+            rustflags.arg(arg);
+        }
+
+        // target specific rustflags take precedence over general rustflags
+        if let Some(target_rustflags) =
+            self.config.target_config.get(&target).map(|t| &t.rustflags[..])
+        {
+            for arg in target_rustflags {
+                rustflags.arg(arg);
+            }
+        }
+
+        rustflags.propagate_cargo_env("RUSTFLAGS");
+
         if build_compiler_stage != 0 {
             if let Ok(s) = env::var("CARGOFLAGS_NOT_BOOTSTRAP") {
                 cargo.args(s.split_whitespace());

src/bootstrap/src/core/config/config.rs

@@ -224,6 +224,7 @@ pub struct Config {
     pub rust_std_features: BTreeSet<String>,
     pub rust_break_on_ice: bool,
     pub rust_parallel_frontend_threads: Option<u32>,
+    pub rust_rustflags: Vec<String>,
 
     pub llvm_profile_use: Option<String>,
     pub llvm_profile_generate: bool,
@@ -571,6 +572,7 @@ impl Config {
             bootstrap_override_lld_legacy: rust_bootstrap_override_lld_legacy,
             std_features: rust_std_features,
             break_on_ice: rust_break_on_ice,
+            rustflags: rust_rustflags,
         } = toml.rust.unwrap_or_default();
 
         let Llvm {
@@ -854,6 +856,7 @@ impl Config {
                     sanitizers: target_sanitizers,
                     profiler: target_profiler,
                     rpath: target_rpath,
+                    rustflags: target_rustflags,
                     crt_static: target_crt_static,
                     musl_root: target_musl_root,
                     musl_libdir: target_musl_libdir,
@@ -937,6 +940,7 @@ impl Config {
                 target.sanitizers = target_sanitizers;
                 target.profiler = target_profiler;
                 target.rpath = target_rpath;
+                target.rustflags = target_rustflags.unwrap_or_default();
                 target.optimized_compiler_builtins = target_optimized_compiler_builtins;
                 target.jemalloc = target_jemalloc;
                 if let Some(backends) = target_codegen_backends {
@@ -1431,6 +1435,7 @@ impl Config {
             rust_randomize_layout: rust_randomize_layout.unwrap_or(false),
             rust_remap_debuginfo: rust_remap_debuginfo.unwrap_or(false),
             rust_rpath: rust_rpath.unwrap_or(true),
+            rust_rustflags: rust_rustflags.unwrap_or_default(),
             rust_stack_protector,
             rust_std_features: rust_std_features
                 .unwrap_or(BTreeSet::from([String::from("panic-unwind")])),

src/bootstrap/src/core/config/toml/rust.rs

@@ -33,6 +33,7 @@ define_config! {
         channel: Option<String> = "channel",
         musl_root: Option<String> = "musl-root",
         rpath: Option<bool> = "rpath",
+        rustflags: Option<Vec<String>> = "rustflags",
         strip: Option<bool> = "strip",
         frame_pointers: Option<bool> = "frame-pointers",
         stack_protector: Option<String> = "stack-protector",
@@ -373,6 +374,7 @@ pub fn check_incompatible_options_for_ci_rustc(
         parallel_frontend_threads: _,
         bootstrap_override_lld: _,
         bootstrap_override_lld_legacy: _,
+        rustflags: _,
     } = ci_rust_config;
 
     // There are two kinds of checks for CI rustc incompatible options:

src/bootstrap/src/core/config/toml/target.rs

@@ -37,6 +37,7 @@ define_config! {
         sanitizers: Option<bool> = "sanitizers",
         profiler: Option<StringOrBool> = "profiler",
         rpath: Option<bool> = "rpath",
+        rustflags: Option<Vec<String>> = "rustflags",
         crt_static: Option<bool> = "crt-static",
         musl_root: Option<String> = "musl-root",
         musl_libdir: Option<String> = "musl-libdir",
@@ -70,6 +71,7 @@ pub struct Target {
     pub sanitizers: Option<bool>,
     pub profiler: Option<StringOrBool>,
     pub rpath: Option<bool>,
+    pub rustflags: Vec<String>,
     pub crt_static: Option<bool>,
     pub musl_root: Option<PathBuf>,
     pub musl_libdir: Option<PathBuf>,

src/bootstrap/src/utils/change_tracker.rs

@@ -581,4 +581,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "The `build.python` option is now respected on macOS (previously ignored and forced to be /usr/bin/python3).",
     },
+    ChangeInfo {
+        change_id: 148795,
+        severity: ChangeSeverity::Info,
+        summary: "New options `rust.rustflags` for all targets and `rustflags` par target that will pass specified flags to rustc for all stages. Target specific flags override (are passed after) global `rust.rustflags` ones.",
+    },
 ];