[experiment] Build the compiler with panic=abort

compiler/rustc/src/main.rs

@@ -1,4 +1,6 @@
 #![feature(unix_sigpipe)]
+// We need this feature as it changes `dylib` linking behavior and allows us to link to `rustc_driver`.
+#![feature(rustc_private)]
 
 // A note about jemalloc: rustc uses jemalloc when built for CI and
 // distribution. The obvious way to do this is with the `#[global_allocator]`

compiler/rustc_metadata/messages.ftl

@@ -41,6 +41,9 @@ metadata_crate_dep_multiple =
 metadata_crate_dep_not_static =
     `{$crate_name}` was unavailable as a static crate, preventing fully static linking
 
+metadata_crate_dep_rustc_driver =
+    `feature(rustc_private)` is needed to link to the compiler's `rustc_driver` library
+
 metadata_crate_location_unknown_type =
     extern location for {$crate_name} is of an unknown type: {$path}
 

compiler/rustc_metadata/src/dependency_format.rs

@@ -54,16 +54,18 @@
 use crate::creader::CStore;
 use crate::errors::{
     BadPanicStrategy, CrateDepMultiple, IncompatiblePanicInDropStrategy, LibRequired,
-    NonStaticCrateDep, RequiredPanicStrategy, RlibRequired, RustcLibRequired, TwoPanicRuntimes,
+    NonStaticCrateDep, RequiredPanicStrategy, RlibRequired, RustcDriverHelp, RustcLibRequired,
+    TwoPanicRuntimes,
 };
 
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::CrateNum;
 use rustc_middle::middle::dependency_format::{Dependencies, DependencyList, Linkage};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::CrateType;
 use rustc_session::cstore::CrateDepKind;
 use rustc_session::cstore::LinkagePreference::{self, RequireDynamic, RequireStatic};
+use rustc_span::sym;
 
 pub(crate) fn calculate(tcx: TyCtxt<'_>) -> Dependencies {
     tcx.crate_types()
@@ -158,25 +160,49 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
         Linkage::Dynamic | Linkage::IncludedFromDylib => {}
     }
 
+    let all_dylibs = || {
+        tcx.crates(()).iter().filter(|&&cnum| {
+            !tcx.dep_kind(cnum).macros_only() && tcx.used_crate_source(cnum).dylib.is_some()
+        })
+    };
+
+    let mut upstream_in_dylibs = FxHashSet::default();
+
+    if tcx.features().rustc_private {
+        // We need this to prevent users of `rustc_driver` from linking to dynamically to `std`
+        // which does not work as `std` is also statically linked into `rustc_driver`.
+
+        // Find all libraries statically linked to upstream dylibs.
+        for &cnum in all_dylibs() {
+            let deps = tcx.dylib_dependency_formats(cnum);
+            for &(depnum, style) in deps.iter() {
+                if let RequireStatic = style {
+                    upstream_in_dylibs.insert(depnum);
+                }
+            }
+        }
+    }
+
     let mut formats = FxHashMap::default();
 
     // Sweep all crates for found dylibs. Add all dylibs, as well as their
     // dependencies, ensuring there are no conflicts. The only valid case for a
     // dependency to be relied upon twice is for both cases to rely on a dylib.
-    for &cnum in tcx.crates(()).iter() {
-        if tcx.dep_kind(cnum).macros_only() {
+    for &cnum in all_dylibs() {
+        if upstream_in_dylibs.contains(&cnum) {
+            info!("skipping dylib: {}", tcx.crate_name(cnum));
+            // If this dylib is also available statically linked to another dylib
+            // we try to use that instead.
             continue;
         }
+
         let name = tcx.crate_name(cnum);
-        let src = tcx.used_crate_source(cnum);
-        if src.dylib.is_some() {
-            info!("adding dylib: {}", name);
-            add_library(tcx, cnum, RequireDynamic, &mut formats, &mut unavailable_as_static);
-            let deps = tcx.dylib_dependency_formats(cnum);
-            for &(depnum, style) in deps.iter() {
-                info!("adding {:?}: {}", style, tcx.crate_name(depnum));
-                add_library(tcx, depnum, style, &mut formats, &mut unavailable_as_static);
-            }
+        info!("adding dylib: {}", name);
+        add_library(tcx, cnum, RequireDynamic, &mut formats, &mut unavailable_as_static);
+        let deps = tcx.dylib_dependency_formats(cnum);
+        for &(depnum, style) in deps.iter() {
+            info!("adding {:?}: {}", style, tcx.crate_name(depnum));
+            add_library(tcx, depnum, style, &mut formats, &mut unavailable_as_static);
         }
     }
 
@@ -266,12 +292,15 @@ fn add_library(
             // This error is probably a little obscure, but I imagine that it
             // can be refined over time.
             if link2 != link || link == RequireStatic {
+                let linking_to_rustc_driver = tcx.sess.psess.unstable_features.is_nightly_build()
+                    && tcx.crates(()).iter().any(|&cnum| tcx.crate_name(cnum) == sym::rustc_driver);
                 tcx.dcx().emit_err(CrateDepMultiple {
                     crate_name: tcx.crate_name(cnum),
                     non_static_deps: unavailable_as_static
                         .drain(..)
                         .map(|cnum| NonStaticCrateDep { crate_name: tcx.crate_name(cnum) })
                         .collect(),
+                    rustc_driver_help: linking_to_rustc_driver.then_some(RustcDriverHelp),
                 });
             }
         }

compiler/rustc_metadata/src/errors.rs

@@ -40,6 +40,8 @@ pub struct CrateDepMultiple {
     pub crate_name: Symbol,
     #[subdiagnostic]
     pub non_static_deps: Vec<NonStaticCrateDep>,
+    #[subdiagnostic]
+    pub rustc_driver_help: Option<RustcDriverHelp>,
 }
 
 #[derive(Subdiagnostic)]
@@ -48,6 +50,10 @@ pub struct NonStaticCrateDep {
     pub crate_name: Symbol,
 }
 
+#[derive(Subdiagnostic)]
+#[help(metadata_crate_dep_rustc_driver)]
+pub struct RustcDriverHelp;
+
 #[derive(Diagnostic)]
 #[diag(metadata_two_panic_runtimes)]
 pub struct TwoPanicRuntimes {

compiler/rustc_span/src/symbol.rs

@@ -1573,6 +1573,7 @@ symbols! {
         rustc_dirty,
         rustc_do_not_const_check,
         rustc_doc_primitive,
+        rustc_driver,
         rustc_dummy,
         rustc_dump_env_program_clauses,
         rustc_dump_program_clauses,

src/bootstrap/src/bin/rustc.rs

@@ -91,6 +91,23 @@ fn main() {
         rustc_real
     };
 
+    // Get the name of the crate we're compiling, if any.
+    let crate_name = arg("--crate-name");
+
+    // We want everything statically linked into `rustc_driver`, so remove `-C prefer-dynamic`
+    if crate_name == Some("rustc_driver") && stage != "0" {
+        // Remove `-C prefer-dynamic` to link `std` statically into `rustc_driver`
+        if let Some(pos) = args.iter().enumerate().position(|(i, a)| {
+            a == "-C" && args.get(i + 1).map(|a| a == "prefer-dynamic").unwrap_or(false)
+        }) {
+            args.remove(pos);
+            args.remove(pos);
+        }
+        if let Some(pos) = args.iter().position(|a| a == "-Cprefer-dynamic") {
+            args.remove(pos);
+        }
+    }
+
     let mut cmd = if let Some(wrapper) = env::var_os("RUSTC_WRAPPER_REAL") {
         let mut cmd = Command::new(wrapper);
         cmd.arg(rustc_driver);
@@ -100,9 +117,6 @@ fn main() {
     };
     cmd.args(&args).env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
-    // Get the name of the crate we're compiling, if any.
-    let crate_name = arg("--crate-name");
-
     if let Some(crate_name) = crate_name {
         if let Some(target) = env::var_os("RUSTC_TIME") {
             if target == "all"

src/bootstrap/src/core/build_steps/compile.rs

@@ -1079,6 +1079,11 @@ pub fn rustc_cargo(
         ));
     }
 
+    if compiler.stage != 0 {
+        cargo.rustflag("-Cpanic=abort");
+        cargo.rustflag("-Cforce-unwind-tables=yes");
+    }
+
     rustc_cargo_env(builder, cargo, target, compiler.stage);
 }
 
@@ -1780,7 +1785,12 @@ impl Step for Assemble {
         let src_libdir = builder.sysroot_libdir(build_compiler, host);
         for f in builder.read_dir(&src_libdir) {
             let filename = f.file_name().into_string().unwrap();
-            if (is_dylib(&filename) || is_debug_info(&filename)) && !proc_macros.contains(&filename)
+            let can_be_rustc_dep = filename.starts_with("rustc_driver-")
+                || filename.starts_with("librustc_driver-")
+                || build_compiler.stage == 0;
+            if can_be_rustc_dep
+                && (is_dylib(&filename) || is_debug_info(&filename))
+                && !proc_macros.contains(&filename)
             {
                 builder.copy_link(&f.path(), &rustc_libdir.join(&filename));
             }

src/bootstrap/src/core/build_steps/tool.rs

@@ -166,6 +166,19 @@ pub fn prepare_tool_cargo(
         }
     }
 
+    if compiler.stage != 0 {
+        if path.ends_with("rls")
+            || path.ends_with("clippy")
+            || path.ends_with("miri")
+            || path.ends_with("rustfmt")
+            || path.ends_with("rustdoc")
+            || path.ends_with("rustdoc-tool")
+        {
+            cargo.rustflag("-Cpanic=abort");
+            cargo.rustflag("-Cforce-unwind-tables=yes");
+        }
+    }
+
     // clippy tests need to know about the stage sysroot. Set them consistently while building to
     // avoid rebuilding when running tests.
     cargo.env("SYSROOT", builder.sysroot(compiler));

src/bootstrap/src/core/builder.rs

@@ -2064,7 +2064,7 @@ impl<'a> Builder<'a> {
         // When we build Rust dylibs they're all intended for intermediate
         // usage, so make sure we pass the -Cprefer-dynamic flag instead of
         // linking all deps statically into the dylib.
-        if matches!(mode, Mode::Std | Mode::Rustc) {
+        if matches!(mode, Mode::Std) {
             rustflags.arg("-Cprefer-dynamic");
         }
 

src/ci/github-actions/jobs.yml

@@ -84,7 +84,7 @@ pr:
 try:
   - image: dist-x86_64-linux
     env:
-      CODEGEN_BACKENDS: llvm,cranelift
+      CODEGEN_BACKENDS: llvm
     <<: *job-linux-16c
 
 # Main CI jobs that have to be green to merge a commit into master

src/tools/clippy/src/main.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
 // warn on lints, that are included in `rust-lang/rust`s bootstrap
 #![warn(rust_2018_idioms, unused_lifetimes)]

src/tools/clippy/tests/compile-test.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
 #![feature(lazy_cell)]
 #![feature(is_sorted)]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]

src/tools/rustdoc/main.rs

@@ -1,4 +1,6 @@
 #![feature(unix_sigpipe)]
+// We need this feature as it changes `dylib` linking behavior and allows us to link to `rustc_driver`.
+#![feature(rustc_private)]
 
 #[unix_sigpipe = "sig_dfl"]
 fn main() {

src/tools/rustfmt/src/git-rustfmt/main.rs

@@ -1,3 +1,7 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
+
 #[macro_use]
 extern crate tracing;