Auto merge of rust-lang#55023 - euclio:llvm-error-handler, r=cuviper

Exit with code 101 on fatal codegen errors

Fixes rust-lang#54992.

This PR installs a custom fatal error handler that prints the error from LLVM and exits with 101. There should be no visible change in the output from LLVM. This allows distinguishing a fatal LLVM error with a compilation error by exit code.

This PR also modifies the LLVM codegen backend to ICE instead of emitting a fatal error when encountering a LLVM worker thread panic for the same reason.

r? @cuviper

Author: bors

src/librustc_codegen_llvm/back/write.rs

@@ -2031,9 +2031,7 @@ fn start_executing_work(tcx: TyCtxt,
                     main_thread_worker_state = MainThreadWorkerState::Idle;
                 }
                 Message::Done { result: Err(()), worker_id: _ } => {
-                    shared_emitter.fatal("aborting due to worker thread failure");
-                    // Exit the coordinator thread
-                    return Err(())
+                    bug!("worker thread panicked");
                 }
                 Message::CodegenItem => {
                     bug!("the coordinator should not receive codegen requests")
@@ -2392,7 +2390,7 @@ impl OngoingCodegen {
                 panic!("expected abort due to worker thread errors")
             },
             Err(_) => {
-                sess.fatal("Error during codegen/LLVM phase.");
+                bug!("panic during codegen/LLVM phase");
             }
         };
 

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -482,6 +482,8 @@ pub mod debuginfo {
 extern { pub type ModuleBuffer; }
 
 extern "C" {
+    pub fn LLVMRustInstallFatalErrorHandler();
+
     // Create and destroy contexts.
     pub fn LLVMRustContextCreate(shouldDiscardNames: bool) -> &'static mut Context;
     pub fn LLVMContextDispose(C: &'static mut Context);

src/librustc_codegen_llvm/llvm_util.rs

@@ -56,6 +56,8 @@ unsafe fn configure_llvm(sess: &Session) {
     let mut llvm_c_strs = Vec::with_capacity(n_args + 1);
     let mut llvm_args = Vec::with_capacity(n_args + 1);
 
+    llvm::LLVMRustInstallFatalErrorHandler();
+
     {
         let mut add = |arg: &str| {
             let s = CString::new(arg).unwrap();

src/rustllvm/RustWrapper.cpp

@@ -17,6 +17,7 @@
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Bitcode/BitcodeWriterPass.h"
+#include "llvm/Support/Signals.h"
 
 #include "llvm/IR/CallSite.h"
 
@@ -26,6 +27,8 @@
 #include <cstdlib>
 #endif
 
+#include <iostream>
+
 //===----------------------------------------------------------------------===
 //
 // This file defines alternate interfaces to core functions that are more
@@ -62,6 +65,27 @@ static AtomicOrdering fromRust(LLVMAtomicOrdering Ordering) {
 
 static LLVM_THREAD_LOCAL char *LastError;
 
+// Custom error handler for fatal LLVM errors.
+//
+// Notably it exits the process with code 101, unlike LLVM's default of 1.
+static void FatalErrorHandler(void *UserData,
+                              const std::string& Reason,
+                              bool GenCrashDiag) {
+  // Do the same thing that the default error handler does.
+  std::cerr << "LLVM ERROR: " << Reason << std::endl;
+
+  // Since this error handler exits the process, we have to run any cleanup that
+  // LLVM would run after handling the error. This might change with an LLVM
+  // upgrade.
+  sys::RunInterruptHandlers();
+
+  exit(101);
+}
+
+extern "C" void LLVMRustInstallFatalErrorHandler() {
+  install_fatal_error_handler(FatalErrorHandler);
+}
+
 extern "C" LLVMMemoryBufferRef
 LLVMRustCreateMemoryBufferWithContentsOfFile(const char *Path) {
   ErrorOr<std::unique_ptr<MemoryBuffer>> BufOr =