[clang] [llvm] [clang][MBD] set up module build daemon infrastructure (PR #67562)

[Michael Spencer via llvm-commits]

================
@@ -0,0 +1,289 @@
+//===------- cc1modbuildd_main.cpp - Clang CC1 Module Build Daemon --------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/ModuleBuildDaemon/SocketSupport.h"
+#include "clang/Tooling/ModuleBuildDaemon/Utils.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/ThreadPool.h"
+
+#include <csignal>
+#include <cstdbool>
+#include <cstdio>
+#include <cstring>
+#include <fstream>
+#include <optional>
+#include <string>
+#include <system_error>
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+
+using namespace llvm;
+using namespace clang::tooling::cc1modbuildd;
+
+// Create unbuffered STDOUT stream so that any logging done by the module build
+// daemon can be viewed without having to terminate the process
+static raw_fd_ostream &unbuff_outs() {
+  static raw_fd_ostream S(fileno(stdout), false, true);
+  return S;
+}
+
+static bool LogVerbose = false;
+static void logVerbose(const llvm::Twine &message) {
+  if (LogVerbose) {
+    unbuff_outs() << message << '\n';
+  }
+}
+
+static void modifySignals(decltype(SIG_DFL) handler) {
+
+  if (std::signal(SIGTERM, handler) == SIG_ERR) {
+    errs() << "failed to handle SIGTERM" << '\n';
+    exit(EXIT_FAILURE);
+  }
+
+  if (std::signal(SIGINT, handler) == SIG_ERR) {
+    errs() << "failed to handle SIGINT" << '\n';
+    exit(EXIT_FAILURE);
+  }
+
+#ifdef SIGHUP
+  if (::signal(SIGHUP, SIG_IGN) == SIG_ERR) {
+    errs() << "failed to handle SIGHUP" << '\n';
+    exit(EXIT_FAILURE);
+  }
+#endif
+}
+
+namespace {
+
+class ModuleBuildDaemonServer {
+public:
+  SmallString<256> SocketPath;
+  SmallString<256> Stderr; // path to stderr
+  SmallString<256> Stdout; // path to stdout
+
+  explicit ModuleBuildDaemonServer(StringRef Path)
+      : SocketPath(Path), Stderr(Path), Stdout(Path) {
+    llvm::sys::path::append(SocketPath, SocketFileName);
+    llvm::sys::path::append(Stdout, StdoutFileName);
+    llvm::sys::path::append(Stderr, StderrFileName);
+  }
+
+  void setupDaemonEnv();
+  void createDaemonSocket();
+  void listenForClients();
+
+  static void handleConnection(std::shared_ptr<raw_socket_stream> Connection);
+
+  // TODO: modify so when shutdownDaemon is called the daemon stops accepting
+  // new client connections and waits for all existing client connections to
+  // terminate before closing the file descriptor and exiting
+  void shutdownDaemon() {
+    RunServiceLoop = false;
+    if (ServerListener.has_value())
+      ServerListener.value().shutdown();
+  }
+
+private:
+  std::atomic<bool> RunServiceLoop = true;
+  std::optional<llvm::ListeningSocket> ServerListener;
+};
+
+// Used to handle signals
+ModuleBuildDaemonServer *DaemonPtr = nullptr;
+void handleSignal(int) { DaemonPtr->shutdownDaemon(); }
+} // namespace
+
+// Sets up file descriptors and signals for module build daemon
+void ModuleBuildDaemonServer::setupDaemonEnv() {
+
+#ifdef _WIN32
+  if (std::freopen("NUL", "r", stdin) == NULL) {
+#else
+  if (std::freopen("/dev/null", "r", stdin) == NULL) {
+#endif
+    llvm::errs() << "Failed to close stdin" << '\n';
+    exit(EXIT_FAILURE);
+  }
+
+  if (std::freopen(Stdout.c_str(), "a", stdout) == NULL) {
+    llvm::errs() << "Failed to redirect stdout to " << Stdout << '\n';
+    exit(EXIT_FAILURE);
+  }
+  if (std::freopen(Stderr.c_str(), "a", stderr) == NULL) {
+    llvm::errs() << "Failed to redirect stderr to " << Stderr << '\n';
+    exit(EXIT_FAILURE);
+  }
+
+  modifySignals(handleSignal);
+}
+
+// Creates unix socket for IPC with frontends
+void ModuleBuildDaemonServer::createDaemonSocket() {
+
+  while (true) {
+    Expected<ListeningSocket> MaybeServerListener =
+        llvm::ListeningSocket::createUnix(SocketPath);
+
+    if (llvm::Error Err = MaybeServerListener.takeError()) {
+      llvm::handleAllErrors(std::move(Err), [&](const llvm::StringError &SE) {
+        std::error_code EC = SE.convertToErrorCode();
+
+        // Exit successfully if the socket address is already in use. When
+        // TUs are compiled in parallel, until the socket file is created, all
+        // clang invocations will try to spawn a module build daemon.
+#ifdef _WIN32
+        if (EC.value() == WSAEADDRINUSE) {
+#else
+        if (EC == std::errc::address_in_use) {
+#endif
+          exit(EXIT_SUCCESS);
+        } else if (EC == std::errc::file_exists) {
+          if (std::remove(SocketPath.c_str()) != 0) {
+            llvm::errs() << "Failed to remove " << SocketPath << ": "
+                         << strerror(errno) << '\n';
+            exit(EXIT_FAILURE);
+          }
+          // If a previous module build daemon invocation crashes, the socket
+          // file will need to be removed before the address can be binded to
+          logVerbose("Removing ineligible file: " + SocketPath);
+        } else {
+          llvm::errs() << "MBD failed to create unix socket: "
+                       << SE.getMessage() << ": " << EC.message() << '\n';
+          exit(EXIT_FAILURE);
+        }
+      });
+    } else {
+      logVerbose("MBD created and binded to socket at: " + SocketPath);
+      ServerListener.emplace(std::move(*MaybeServerListener));
+      break;
+    }
+  }
+}
+
+// Function submitted to thread pool with each frontend connection. Not
+// responsible for closing frontend socket connections
+void ModuleBuildDaemonServer::handleConnection(
+    std::shared_ptr<llvm::raw_socket_stream> MovableConnection) {
+
+  llvm::raw_socket_stream &Connection = *MovableConnection;
+
+  // Read request from frontend
+  Expected<HandshakeMsg> MaybeHandshakeMsg =
+      readMsgStructFromSocket<HandshakeMsg>(Connection);
+  if (!MaybeHandshakeMsg) {
+    errs() << "MBD failed to read frontend request: "
+           << llvm::toString(MaybeHandshakeMsg.takeError()) << '\n';
+    return;
+  }
+
+  // Send response to frontend
+  HandshakeMsg Msg(ActionType::HANDSHAKE, StatusType::SUCCESS);
+  if (llvm::Error WriteErr = writeMsgStructToSocket(Connection, Msg)) {
+    errs() << "MBD failed to respond to frontend request: "
+           << llvm::toString(std::move(WriteErr)) << '\n';
+    return;
+  }
+  return;
----------------
Bigcheese wrote:

Don't need the return in the if here.

https://github.com/llvm/llvm-project/pull/67562