Strip unexpected debuginfo from libLLVM.so and librustc_driver.so when not requesting any debuginfo

src/bootstrap/compile.rs

@@ -23,7 +23,7 @@ use crate::builder::crate_description;
 use crate::builder::Cargo;
 use crate::builder::{Builder, Kind, PathSet, RunConfig, ShouldRun, Step, TaskPath};
 use crate::cache::{Interned, INTERNER};
-use crate::config::{LlvmLibunwind, RustcLto, TargetSelection};
+use crate::config::{DebuginfoLevel, LlvmLibunwind, RustcLto, TargetSelection};
 use crate::dist;
 use crate::llvm;
 use crate::tool::SourceType;
@@ -883,16 +883,37 @@ impl Step for Rustc {
             compiler.host,
             target,
         );
+        let stamp = librustc_stamp(builder, compiler, target);
         run_cargo(
             builder,
             cargo,
             vec![],
-            &librustc_stamp(builder, compiler, target),
+            &stamp,
             vec![],
             false,
             true, // Only ship rustc_driver.so and .rmeta files, not all intermediate .rlib files.
         );
 
+        // When building `librustc_driver.so` (like `libLLVM.so`) on linux, it can contain
+        // unexpected debuginfo from dependencies, for example from the C++ standard library used in
+        // our LLVM wrapper. Unless we're explicitly requesting `librustc_driver` to be built with
+        // debuginfo (via the debuginfo level of the executables using it): strip this debuginfo
+        // away after the fact.
+        // FIXME: to make things simpler for now, limit this to the host and target where we know
+        // `strip -g` is both available and will fix the issue, i.e. on a x64 linux host that is not
+        // cross-compiling. Expand this to other appropriate targets in the future.
+        if builder.config.rust_debuginfo_level_rustc == DebuginfoLevel::None
+            && builder.config.rust_debuginfo_level_tools == DebuginfoLevel::None
+            && target == "x86_64-unknown-linux-gnu"
+            && target == builder.config.build
+        {
+            let target_root_dir = stamp.parent().unwrap();
+            let rustc_driver = target_root_dir.join("librustc_driver.so");
+            if rustc_driver.exists() {
+                output(Command::new("strip").arg("--strip-debug").arg(rustc_driver));
+            }
+        }
+
         builder.ensure(RustcLink::from_rustc(
             self,
             builder.compiler(compiler.stage, builder.config.build),

src/bootstrap/config.rs

@@ -50,7 +50,7 @@ pub enum DryRun {
     UserSelected,
 }
 
-#[derive(Copy, Clone, Default)]
+#[derive(Copy, Clone, Default, PartialEq, Eq)]
 pub enum DebuginfoLevel {
     #[default]
     None,

src/bootstrap/llvm.rs

@@ -491,25 +491,56 @@ impl Step for Llvm {
 
         cfg.build();
 
-        // When building LLVM with LLVM_LINK_LLVM_DYLIB for macOS, an unversioned
-        // libLLVM.dylib will be built. However, llvm-config will still look
-        // for a versioned path like libLLVM-14.dylib. Manually create a symbolic
-        // link to make llvm-config happy.
-        if builder.llvm_link_shared() && target.contains("apple-darwin") {
+        // Helper to find the name of LLVM's shared library on darwin and linux.
+        let find_llvm_lib_name = |extension| {
             let mut cmd = Command::new(&res.llvm_config);
             let version = output(cmd.arg("--version"));
             let major = version.split('.').next().unwrap();
-            let lib_name = match llvm_version_suffix {
-                Some(s) => format!("libLLVM-{major}{s}.dylib"),
-                None => format!("libLLVM-{major}.dylib"),
+            let lib_name = match &llvm_version_suffix {
+                Some(version_suffix) => format!("libLLVM-{major}{version_suffix}.{extension}"),
+                None => format!("libLLVM-{major}.{extension}"),
             };
+            lib_name
+        };
 
+        // When building LLVM with LLVM_LINK_LLVM_DYLIB for macOS, an unversioned
+        // libLLVM.dylib will be built. However, llvm-config will still look
+        // for a versioned path like libLLVM-14.dylib. Manually create a symbolic
+        // link to make llvm-config happy.
+        if builder.llvm_link_shared() && target.contains("apple-darwin") {
+            let lib_name = find_llvm_lib_name("dylib");
             let lib_llvm = out_dir.join("build").join("lib").join(lib_name);
             if !lib_llvm.exists() {
                 t!(builder.symlink_file("libLLVM.dylib", &lib_llvm));
             }
         }
 
+        // When building LLVM as a shared library on linux, it can contain unexpected debuginfo:
+        // some can come from the C++ standard library. Unless we're explicitly requesting LLVM to
+        // be built with debuginfo, strip it away after the fact, to make dist artifacts smaller.
+        // FIXME: to make things simpler for now, limit this to the host and target where we know
+        // `strip -g` is both available and will fix the issue, i.e. on a x64 linux host that is not
+        // cross-compiling. Expand this to other appropriate targets in the future.
+        if builder.llvm_link_shared()
+            && builder.config.llvm_optimize
+            && !builder.config.llvm_release_debuginfo
+            && target == "x86_64-unknown-linux-gnu"
+            && target == builder.config.build
+        {
+            // Find the name of the LLVM shared library that we just built.
+            let lib_name = find_llvm_lib_name("so");
+
+            // If the shared library exists in LLVM's `/build/lib/` or `/lib/` folders, strip its
+            // debuginfo. Note: `output` will propagate any errors here.
+            let strip_if_possible = |path: PathBuf| {
+                if path.exists() {
+                    output(Command::new("strip").arg("--strip-debug").arg(path));
+                }
+            };
+            strip_if_possible(out_dir.join("lib").join(&lib_name));
+            strip_if_possible(out_dir.join("build").join("lib").join(&lib_name));
+        }
+
         t!(stamp.write());
 
         res