1 //===-- Host.cpp ------------------------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 // C includes
11 #include <errno.h>
12 #include <limits.h>
13 #include <stdlib.h>
14 #include <sys/types.h>
15 #ifndef _WIN32
16 #include <dlfcn.h>
17 #include <grp.h>
18 #include <netdb.h>
19 #include <pwd.h>
20 #include <sys/stat.h>
21 #include <unistd.h>
22 #endif
23 
24 #if defined(__APPLE__)
25 #include <mach-o/dyld.h>
26 #include <mach/mach_init.h>
27 #include <mach/mach_port.h>
28 #endif
29 
30 #if defined(__linux__) || defined(__FreeBSD__) ||                              \
31     defined(__FreeBSD_kernel__) || defined(__APPLE__) ||                       \
32     defined(__NetBSD__) || defined(__OpenBSD__)
33 #if !defined(__ANDROID__)
34 #include <spawn.h>
35 #endif
36 #include <sys/syscall.h>
37 #include <sys/wait.h>
38 #endif
39 
40 #if defined(__FreeBSD__)
41 #include <pthread_np.h>
42 #endif
43 
44 #if defined(__NetBSD__)
45 #include <lwp.h>
46 #endif
47 
48 #include <csignal>
49 
50 #include "lldb/Host/FileSystem.h"
51 #include "lldb/Host/Host.h"
52 #include "lldb/Host/HostInfo.h"
53 #include "lldb/Host/HostProcess.h"
54 #include "lldb/Host/MonitoringProcessLauncher.h"
55 #include "lldb/Host/ProcessLauncher.h"
56 #include "lldb/Host/ThreadLauncher.h"
57 #include "lldb/Host/posix/ConnectionFileDescriptorPosix.h"
58 #include "lldb/Target/FileAction.h"
59 #include "lldb/Target/ProcessLaunchInfo.h"
60 #include "lldb/Target/UnixSignals.h"
61 #include "lldb/Utility/DataBufferLLVM.h"
62 #include "lldb/Utility/FileSpec.h"
63 #include "lldb/Utility/Log.h"
64 #include "lldb/Utility/Predicate.h"
65 #include "lldb/Utility/Status.h"
66 #include "lldb/lldb-private-forward.h"
67 #include "llvm/ADT/SmallString.h"
68 #include "llvm/ADT/StringSwitch.h"
69 #include "llvm/Support/Errno.h"
70 #include "llvm/Support/FileSystem.h"
71 
72 #if defined(_WIN32)
73 #include "lldb/Host/windows/ConnectionGenericFileWindows.h"
74 #include "lldb/Host/windows/ProcessLauncherWindows.h"
75 #else
76 #include "lldb/Host/posix/ProcessLauncherPosixFork.h"
77 #endif
78 
79 #if defined(__APPLE__)
80 #ifndef _POSIX_SPAWN_DISABLE_ASLR
81 #define _POSIX_SPAWN_DISABLE_ASLR 0x0100
82 #endif
83 
84 extern "C" {
85 int __pthread_chdir(const char *path);
86 int __pthread_fchdir(int fildes);
87 }
88 
89 #endif
90 
91 using namespace lldb;
92 using namespace lldb_private;
93 
94 #if !defined(__APPLE__) && !defined(_WIN32)
95 struct MonitorInfo {
96   lldb::pid_t pid; // The process ID to monitor
97   Host::MonitorChildProcessCallback
98       callback; // The callback function to call when "pid" exits or signals
99   bool monitor_signals; // If true, call the callback when "pid" gets signaled.
100 };
101 
102 static thread_result_t MonitorChildProcessThreadFunction(void *arg);
103 
104 HostThread Host::StartMonitoringChildProcess(
105     const Host::MonitorChildProcessCallback &callback, lldb::pid_t pid,
106     bool monitor_signals) {
107   MonitorInfo *info_ptr = new MonitorInfo();
108 
109   info_ptr->pid = pid;
110   info_ptr->callback = callback;
111   info_ptr->monitor_signals = monitor_signals;
112 
113   char thread_name[256];
114   ::snprintf(thread_name, sizeof(thread_name),
115              "<lldb.host.wait4(pid=%" PRIu64 ")>", pid);
116   return ThreadLauncher::LaunchThread(
117       thread_name, MonitorChildProcessThreadFunction, info_ptr, NULL);
118 }
119 
120 #ifndef __linux__
121 //------------------------------------------------------------------
122 // Scoped class that will disable thread canceling when it is constructed, and
123 // exception safely restore the previous value it when it goes out of scope.
124 //------------------------------------------------------------------
125 class ScopedPThreadCancelDisabler {
126 public:
127   ScopedPThreadCancelDisabler() {
128     // Disable the ability for this thread to be cancelled
129     int err = ::pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &m_old_state);
130     if (err != 0)
131       m_old_state = -1;
132   }
133 
134   ~ScopedPThreadCancelDisabler() {
135     // Restore the ability for this thread to be cancelled to what it
136     // previously was.
137     if (m_old_state != -1)
138       ::pthread_setcancelstate(m_old_state, 0);
139   }
140 
141 private:
142   int m_old_state; // Save the old cancelability state.
143 };
144 #endif // __linux__
145 
146 #ifdef __linux__
147 #if defined(__GNUC__) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8))
148 static __thread volatile sig_atomic_t g_usr1_called;
149 #else
150 static thread_local volatile sig_atomic_t g_usr1_called;
151 #endif
152 
153 static void SigUsr1Handler(int) { g_usr1_called = 1; }
154 #endif // __linux__
155 
156 static bool CheckForMonitorCancellation() {
157 #ifdef __linux__
158   if (g_usr1_called) {
159     g_usr1_called = 0;
160     return true;
161   }
162 #else
163   ::pthread_testcancel();
164 #endif
165   return false;
166 }
167 
168 static thread_result_t MonitorChildProcessThreadFunction(void *arg) {
169   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS));
170   const char *function = __FUNCTION__;
171   if (log)
172     log->Printf("%s (arg = %p) thread starting...", function, arg);
173 
174   MonitorInfo *info = (MonitorInfo *)arg;
175 
176   const Host::MonitorChildProcessCallback callback = info->callback;
177   const bool monitor_signals = info->monitor_signals;
178 
179   assert(info->pid <= UINT32_MAX);
180   const ::pid_t pid = monitor_signals ? -1 * getpgid(info->pid) : info->pid;
181 
182   delete info;
183 
184   int status = -1;
185 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__OpenBSD__)
186 #define __WALL 0
187 #endif
188   const int options = __WALL;
189 
190 #ifdef __linux__
191   // This signal is only used to interrupt the thread from waitpid
192   struct sigaction sigUsr1Action;
193   memset(&sigUsr1Action, 0, sizeof(sigUsr1Action));
194   sigUsr1Action.sa_handler = SigUsr1Handler;
195   ::sigaction(SIGUSR1, &sigUsr1Action, nullptr);
196 #endif // __linux__
197 
198   while (1) {
199     log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS);
200     if (log)
201       log->Printf("%s ::waitpid (pid = %" PRIi32 ", &status, options = %i)...",
202                   function, pid, options);
203 
204     if (CheckForMonitorCancellation())
205       break;
206 
207     // Get signals from all children with same process group of pid
208     const ::pid_t wait_pid = ::waitpid(pid, &status, options);
209 
210     if (CheckForMonitorCancellation())
211       break;
212 
213     if (wait_pid == -1) {
214       if (errno == EINTR)
215         continue;
216       else {
217         LLDB_LOG(log,
218                  "arg = {0}, thread exiting because waitpid failed ({1})...",
219                  arg, llvm::sys::StrError());
220         break;
221       }
222     } else if (wait_pid > 0) {
223       bool exited = false;
224       int signal = 0;
225       int exit_status = 0;
226       const char *status_cstr = NULL;
227       if (WIFSTOPPED(status)) {
228         signal = WSTOPSIG(status);
229         status_cstr = "STOPPED";
230       } else if (WIFEXITED(status)) {
231         exit_status = WEXITSTATUS(status);
232         status_cstr = "EXITED";
233         exited = true;
234       } else if (WIFSIGNALED(status)) {
235         signal = WTERMSIG(status);
236         status_cstr = "SIGNALED";
237         if (wait_pid == abs(pid)) {
238           exited = true;
239           exit_status = -1;
240         }
241       } else {
242         status_cstr = "(\?\?\?)";
243       }
244 
245       // Scope for pthread_cancel_disabler
246       {
247 #ifndef __linux__
248         ScopedPThreadCancelDisabler pthread_cancel_disabler;
249 #endif
250 
251         log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS);
252         if (log)
253           log->Printf("%s ::waitpid (pid = %" PRIi32
254                       ", &status, options = %i) => pid = %" PRIi32
255                       ", status = 0x%8.8x (%s), signal = %i, exit_state = %i",
256                       function, pid, options, wait_pid, status, status_cstr,
257                       signal, exit_status);
258 
259         if (exited || (signal != 0 && monitor_signals)) {
260           bool callback_return = false;
261           if (callback)
262             callback_return = callback(wait_pid, exited, signal, exit_status);
263 
264           // If our process exited, then this thread should exit
265           if (exited && wait_pid == abs(pid)) {
266             if (log)
267               log->Printf("%s (arg = %p) thread exiting because pid received "
268                           "exit signal...",
269                           __FUNCTION__, arg);
270             break;
271           }
272           // If the callback returns true, it means this process should exit
273           if (callback_return) {
274             if (log)
275               log->Printf("%s (arg = %p) thread exiting because callback "
276                           "returned true...",
277                           __FUNCTION__, arg);
278             break;
279           }
280         }
281       }
282     }
283   }
284 
285   log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_PROCESS);
286   if (log)
287     log->Printf("%s (arg = %p) thread exiting...", __FUNCTION__, arg);
288 
289   return NULL;
290 }
291 
292 #endif // #if !defined (__APPLE__) && !defined (_WIN32)
293 
294 #if !defined(__APPLE__)
295 
296 void Host::SystemLog(SystemLogType type, const char *format, va_list args) {
297   vfprintf(stderr, format, args);
298 }
299 
300 #endif
301 
302 void Host::SystemLog(SystemLogType type, const char *format, ...) {
303   va_list args;
304   va_start(args, format);
305   SystemLog(type, format, args);
306   va_end(args);
307 }
308 
309 lldb::pid_t Host::GetCurrentProcessID() { return ::getpid(); }
310 
311 #ifndef _WIN32
312 
313 lldb::thread_t Host::GetCurrentThread() {
314   return lldb::thread_t(pthread_self());
315 }
316 
317 const char *Host::GetSignalAsCString(int signo) {
318   switch (signo) {
319   case SIGHUP:
320     return "SIGHUP"; // 1    hangup
321   case SIGINT:
322     return "SIGINT"; // 2    interrupt
323   case SIGQUIT:
324     return "SIGQUIT"; // 3    quit
325   case SIGILL:
326     return "SIGILL"; // 4    illegal instruction (not reset when caught)
327   case SIGTRAP:
328     return "SIGTRAP"; // 5    trace trap (not reset when caught)
329   case SIGABRT:
330     return "SIGABRT"; // 6    abort()
331 #if defined(SIGPOLL)
332 #if !defined(SIGIO) || (SIGPOLL != SIGIO)
333   // Under some GNU/Linux, SIGPOLL and SIGIO are the same. Causing the build to
334   // fail with 'multiple define cases with same value'
335   case SIGPOLL:
336     return "SIGPOLL"; // 7    pollable event ([XSR] generated, not supported)
337 #endif
338 #endif
339 #if defined(SIGEMT)
340   case SIGEMT:
341     return "SIGEMT"; // 7    EMT instruction
342 #endif
343   case SIGFPE:
344     return "SIGFPE"; // 8    floating point exception
345   case SIGKILL:
346     return "SIGKILL"; // 9    kill (cannot be caught or ignored)
347   case SIGBUS:
348     return "SIGBUS"; // 10    bus error
349   case SIGSEGV:
350     return "SIGSEGV"; // 11    segmentation violation
351   case SIGSYS:
352     return "SIGSYS"; // 12    bad argument to system call
353   case SIGPIPE:
354     return "SIGPIPE"; // 13    write on a pipe with no one to read it
355   case SIGALRM:
356     return "SIGALRM"; // 14    alarm clock
357   case SIGTERM:
358     return "SIGTERM"; // 15    software termination signal from kill
359   case SIGURG:
360     return "SIGURG"; // 16    urgent condition on IO channel
361   case SIGSTOP:
362     return "SIGSTOP"; // 17    sendable stop signal not from tty
363   case SIGTSTP:
364     return "SIGTSTP"; // 18    stop signal from tty
365   case SIGCONT:
366     return "SIGCONT"; // 19    continue a stopped process
367   case SIGCHLD:
368     return "SIGCHLD"; // 20    to parent on child stop or exit
369   case SIGTTIN:
370     return "SIGTTIN"; // 21    to readers pgrp upon background tty read
371   case SIGTTOU:
372     return "SIGTTOU"; // 22    like TTIN for output if (tp->t_local&LTOSTOP)
373 #if defined(SIGIO)
374   case SIGIO:
375     return "SIGIO"; // 23    input/output possible signal
376 #endif
377   case SIGXCPU:
378     return "SIGXCPU"; // 24    exceeded CPU time limit
379   case SIGXFSZ:
380     return "SIGXFSZ"; // 25    exceeded file size limit
381   case SIGVTALRM:
382     return "SIGVTALRM"; // 26    virtual time alarm
383   case SIGPROF:
384     return "SIGPROF"; // 27    profiling time alarm
385 #if defined(SIGWINCH)
386   case SIGWINCH:
387     return "SIGWINCH"; // 28    window size changes
388 #endif
389 #if defined(SIGINFO)
390   case SIGINFO:
391     return "SIGINFO"; // 29    information request
392 #endif
393   case SIGUSR1:
394     return "SIGUSR1"; // 30    user defined signal 1
395   case SIGUSR2:
396     return "SIGUSR2"; // 31    user defined signal 2
397   default:
398     break;
399   }
400   return NULL;
401 }
402 
403 #endif
404 
405 #if !defined(__APPLE__) // see Host.mm
406 
407 bool Host::GetBundleDirectory(const FileSpec &file, FileSpec &bundle) {
408   bundle.Clear();
409   return false;
410 }
411 
412 bool Host::ResolveExecutableInBundle(FileSpec &file) { return false; }
413 #endif
414 
415 #ifndef _WIN32
416 
417 FileSpec Host::GetModuleFileSpecForHostAddress(const void *host_addr) {
418   FileSpec module_filespec;
419 #if !defined(__ANDROID__)
420   Dl_info info;
421   if (::dladdr(host_addr, &info)) {
422     if (info.dli_fname) {
423       module_filespec.SetFile(info.dli_fname, FileSpec::Style::native);
424       FileSystem::Instance().Resolve(module_filespec);
425     }
426   }
427 #endif
428   return module_filespec;
429 }
430 
431 #endif
432 
433 #if !defined(__linux__)
434 bool Host::FindProcessThreads(const lldb::pid_t pid, TidMap &tids_to_attach) {
435   return false;
436 }
437 #endif
438 
439 struct ShellInfo {
440   ShellInfo()
441       : process_reaped(false), pid(LLDB_INVALID_PROCESS_ID), signo(-1),
442         status(-1) {}
443 
444   lldb_private::Predicate<bool> process_reaped;
445   lldb::pid_t pid;
446   int signo;
447   int status;
448 };
449 
450 static bool
451 MonitorShellCommand(std::shared_ptr<ShellInfo> shell_info, lldb::pid_t pid,
452                     bool exited, // True if the process did exit
453                     int signo,   // Zero for no signal
454                     int status)  // Exit value of process if signal is zero
455 {
456   shell_info->pid = pid;
457   shell_info->signo = signo;
458   shell_info->status = status;
459   // Let the thread running Host::RunShellCommand() know that the process
460   // exited and that ShellInfo has been filled in by broadcasting to it
461   shell_info->process_reaped.SetValue(true, eBroadcastAlways);
462   return true;
463 }
464 
465 Status Host::RunShellCommand(const char *command, const FileSpec &working_dir,
466                              int *status_ptr, int *signo_ptr,
467                              std::string *command_output_ptr,
468                              const Timeout<std::micro> &timeout,
469                              bool run_in_default_shell) {
470   return RunShellCommand(Args(command), working_dir, status_ptr, signo_ptr,
471                          command_output_ptr, timeout, run_in_default_shell);
472 }
473 
474 Status Host::RunShellCommand(const Args &args, const FileSpec &working_dir,
475                              int *status_ptr, int *signo_ptr,
476                              std::string *command_output_ptr,
477                              const Timeout<std::micro> &timeout,
478                              bool run_in_default_shell) {
479   Status error;
480   ProcessLaunchInfo launch_info;
481   launch_info.SetArchitecture(HostInfo::GetArchitecture());
482   if (run_in_default_shell) {
483     // Run the command in a shell
484     launch_info.SetShell(HostInfo::GetDefaultShell());
485     launch_info.GetArguments().AppendArguments(args);
486     const bool localhost = true;
487     const bool will_debug = false;
488     const bool first_arg_is_full_shell_command = false;
489     launch_info.ConvertArgumentsForLaunchingInShell(
490         error, localhost, will_debug, first_arg_is_full_shell_command, 0);
491   } else {
492     // No shell, just run it
493     const bool first_arg_is_executable = true;
494     launch_info.SetArguments(args, first_arg_is_executable);
495   }
496 
497   if (working_dir)
498     launch_info.SetWorkingDirectory(working_dir);
499   llvm::SmallString<PATH_MAX> output_file_path;
500 
501   if (command_output_ptr) {
502     // Create a temporary file to get the stdout/stderr and redirect the output
503     // of the command into this file. We will later read this file if all goes
504     // well and fill the data into "command_output_ptr"
505     if (FileSpec tmpdir_file_spec = HostInfo::GetProcessTempDir()) {
506       tmpdir_file_spec.AppendPathComponent("lldb-shell-output.%%%%%%");
507       llvm::sys::fs::createUniqueFile(tmpdir_file_spec.GetPath(),
508                                       output_file_path);
509     } else {
510       llvm::sys::fs::createTemporaryFile("lldb-shell-output.%%%%%%", "",
511                                          output_file_path);
512     }
513   }
514 
515   FileSpec output_file_spec(output_file_path.c_str());
516 
517   launch_info.AppendSuppressFileAction(STDIN_FILENO, true, false);
518   if (output_file_spec) {
519     launch_info.AppendOpenFileAction(STDOUT_FILENO, output_file_spec, false,
520                                      true);
521     launch_info.AppendDuplicateFileAction(STDOUT_FILENO, STDERR_FILENO);
522   } else {
523     launch_info.AppendSuppressFileAction(STDOUT_FILENO, false, true);
524     launch_info.AppendSuppressFileAction(STDERR_FILENO, false, true);
525   }
526 
527   std::shared_ptr<ShellInfo> shell_info_sp(new ShellInfo());
528   const bool monitor_signals = false;
529   launch_info.SetMonitorProcessCallback(
530       std::bind(MonitorShellCommand, shell_info_sp, std::placeholders::_1,
531                 std::placeholders::_2, std::placeholders::_3,
532                 std::placeholders::_4),
533       monitor_signals);
534 
535   error = LaunchProcess(launch_info);
536   const lldb::pid_t pid = launch_info.GetProcessID();
537 
538   if (error.Success() && pid == LLDB_INVALID_PROCESS_ID)
539     error.SetErrorString("failed to get process ID");
540 
541   if (error.Success()) {
542     if (!shell_info_sp->process_reaped.WaitForValueEqualTo(true, timeout)) {
543       error.SetErrorString("timed out waiting for shell command to complete");
544 
545       // Kill the process since it didn't complete within the timeout specified
546       Kill(pid, SIGKILL);
547       // Wait for the monitor callback to get the message
548       shell_info_sp->process_reaped.WaitForValueEqualTo(
549           true, std::chrono::seconds(1));
550     } else {
551       if (status_ptr)
552         *status_ptr = shell_info_sp->status;
553 
554       if (signo_ptr)
555         *signo_ptr = shell_info_sp->signo;
556 
557       if (command_output_ptr) {
558         command_output_ptr->clear();
559         uint64_t file_size =
560             FileSystem::Instance().GetByteSize(output_file_spec);
561         if (file_size > 0) {
562           if (file_size > command_output_ptr->max_size()) {
563             error.SetErrorStringWithFormat(
564                 "shell command output is too large to fit into a std::string");
565           } else {
566             auto Buffer =
567                 FileSystem::Instance().CreateDataBuffer(output_file_spec);
568             if (error.Success())
569               command_output_ptr->assign(Buffer->GetChars(),
570                                          Buffer->GetByteSize());
571           }
572         }
573       }
574     }
575   }
576 
577   llvm::sys::fs::remove(output_file_spec.GetPath());
578   return error;
579 }
580 
581 // The functions below implement process launching for non-Apple-based
582 // platforms
583 #if !defined(__APPLE__)
584 Status Host::LaunchProcess(ProcessLaunchInfo &launch_info) {
585   std::unique_ptr<ProcessLauncher> delegate_launcher;
586 #if defined(_WIN32)
587   delegate_launcher.reset(new ProcessLauncherWindows());
588 #else
589   delegate_launcher.reset(new ProcessLauncherPosixFork());
590 #endif
591   MonitoringProcessLauncher launcher(std::move(delegate_launcher));
592 
593   Status error;
594   HostProcess process = launcher.LaunchProcess(launch_info, error);
595 
596   // TODO(zturner): It would be better if the entire HostProcess were returned
597   // instead of writing it into this structure.
598   launch_info.SetProcessID(process.GetProcessId());
599 
600   return error;
601 }
602 #endif // !defined(__APPLE__)
603 
604 #ifndef _WIN32
605 void Host::Kill(lldb::pid_t pid, int signo) { ::kill(pid, signo); }
606 
607 #endif
608 
609 #if !defined(__APPLE__)
610 bool Host::OpenFileInExternalEditor(const FileSpec &file_spec,
611                                     uint32_t line_no) {
612   return false;
613 }
614 
615 #endif
616 
617 const UnixSignalsSP &Host::GetUnixSignals() {
618   static const auto s_unix_signals_sp =
619       UnixSignals::Create(HostInfo::GetArchitecture());
620   return s_unix_signals_sp;
621 }
622 
623 std::unique_ptr<Connection> Host::CreateDefaultConnection(llvm::StringRef url) {
624 #if defined(_WIN32)
625   if (url.startswith("file://"))
626     return std::unique_ptr<Connection>(new ConnectionGenericFile());
627 #endif
628   return std::unique_ptr<Connection>(new ConnectionFileDescriptor());
629 }
630 
631 #if defined(LLVM_ON_UNIX)
632 WaitStatus WaitStatus::Decode(int wstatus) {
633   if (WIFEXITED(wstatus))
634     return {Exit, uint8_t(WEXITSTATUS(wstatus))};
635   else if (WIFSIGNALED(wstatus))
636     return {Signal, uint8_t(WTERMSIG(wstatus))};
637   else if (WIFSTOPPED(wstatus))
638     return {Stop, uint8_t(WSTOPSIG(wstatus))};
639   llvm_unreachable("Unknown wait status");
640 }
641 #endif
642 
643 void llvm::format_provider<WaitStatus>::format(const WaitStatus &WS,
644                                                raw_ostream &OS,
645                                                StringRef Options) {
646   if (Options == "g") {
647     char type;
648     switch (WS.type) {
649     case WaitStatus::Exit:
650       type = 'W';
651       break;
652     case WaitStatus::Signal:
653       type = 'X';
654       break;
655     case WaitStatus::Stop:
656       type = 'S';
657       break;
658     }
659     OS << formatv("{0}{1:x-2}", type, WS.status);
660     return;
661   }
662 
663   assert(Options.empty());
664   const char *desc;
665   switch(WS.type) {
666   case WaitStatus::Exit:
667     desc = "Exited with status";
668     break;
669   case WaitStatus::Signal:
670     desc = "Killed by signal";
671     break;
672   case WaitStatus::Stop:
673     desc = "Stopped by signal";
674     break;
675   }
676   OS << desc << " " << int(WS.status);
677 }
678