bootstrap: add std_features config to rust section

Author: shrirambalaji

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

@@ -287,6 +287,7 @@ pub struct Config {
     pub rust_profile_generate: Option<String>,
     pub rust_lto: RustcLto,
     pub rust_validate_mir_opts: Option<u32>,
+    pub rust_std_features: Option<Vec<String>>,
     pub llvm_profile_use: Option<String>,
     pub llvm_profile_generate: bool,
     pub llvm_libunwind_default: Option<LlvmLibunwind>,
@@ -1141,6 +1142,7 @@ define_config! {
         download_rustc: Option<StringOrBool> = "download-rustc",
         lto: Option<String> = "lto",
         validate_mir_opts: Option<u32> = "validate-mir-opts",
+        std_features: Option<Vec<String>> = "std_features",
     }
 }
 
@@ -1621,6 +1623,7 @@ impl Config {
         let mut optimize = None;
         let mut omit_git_hash = None;
         let mut lld_enabled = None;
+        let mut std_features = None;
 
         let mut is_user_configured_rust_channel = false;
 
@@ -1679,6 +1682,7 @@ impl Config {
                 stack_protector,
                 strip,
                 lld_mode,
+                std_features: std_features_toml,
             } = rust;
 
             is_user_configured_rust_channel = channel.is_some();
@@ -1698,6 +1702,7 @@ impl Config {
             debuginfo_level_tools = debuginfo_level_tools_toml;
             debuginfo_level_tests = debuginfo_level_tests_toml;
             lld_enabled = lld_enabled_toml;
+            std_features = std_features_toml;
 
             optimize = optimize_toml;
             omit_git_hash = omit_git_hash_toml;
@@ -2103,6 +2108,9 @@ impl Config {
             );
         }
 
+        // std_features chosen during bootstrap
+        config.rust_std_features = std_features;
+
         let default = debug == Some(true);
         config.rust_debug_assertions = debug_assertions.unwrap_or(default);
         config.rust_debug_assertions_std =
@@ -2949,6 +2957,7 @@ fn check_incompatible_options_for_ci_rustc(
         download_rustc: _,
         validate_mir_opts: _,
         frame_pointers: _,
+        std_features: _,
     } = ci_rust_config;
 
     // There are two kinds of checks for CI rustc incompatible options:

src/bootstrap/src/lib.rs

@@ -655,27 +655,37 @@ impl Build {
     }
 
     /// Gets the space-separated set of activated features for the standard
-    /// library.
+    /// library. This can be configured with the `std_features` key in config.toml.
     fn std_features(&self, target: TargetSelection) -> String {
-        let mut features = " panic-unwind".to_string();
+        let mut features = if let Some(features) = &self.config.rust_std_features {
+            features.iter().map(|s| s.as_ref()).collect::<Vec<&str>>()
+        } else {
+            vec![]
+        };
+
+        if !features.contains(&"panic-unwind") {
+            features.push("panic-unwind");
+        }
 
         match self.config.llvm_libunwind(target) {
-            LlvmLibunwind::InTree => features.push_str(" llvm-libunwind"),
-            LlvmLibunwind::System => features.push_str(" system-llvm-libunwind"),
+            LlvmLibunwind::InTree => features.push("llvm-libunwind"),
+            LlvmLibunwind::System => features.push("system-llvm-libunwind"),
             LlvmLibunwind::No => {}
         }
         if self.config.backtrace {
-            features.push_str(" backtrace");
+            features.push("backtrace");
         }
         if self.config.profiler_enabled(target) {
-            features.push_str(" profiler");
+            features.push("profiler");
         }
         // Generate memcpy, etc.  FIXME: Remove this once compiler-builtins
         // automatically detects this target.
         if target.contains("zkvm") {
-            features.push_str(" compiler-builtins-mem");
+            features.push("compiler-builtins-mem");
         }
-        features
+
+        // remove duplicates
+        features.into_iter().collect::<HashSet<_>>().into_iter().collect::<Vec<_>>().join(" ")
     }
 
     /// Gets the space-separated set of activated features for the compiler.