src/support/forkedcall.C

   1 /**
   2  *  \file forkedcall.C
   3  *  Copyright 2002 the LyX Team
   4  *  Read the file COPYING
   5  *
   6  * \author Asger Alstrup
   7  *
   8  * Interface cleaned up by
   9  * \author Angus Leeming <a.leeming@ic.ac.uk>
  10  *
  11  * An instance of Class Forkedcall represents a single child process.
  12  *
  13  * Class Forkedcall uses fork() and execvp() to lauch the child process.
  14  *
  15  * Once launched, control is returned immediately to the parent process
  16  * but a Signal can be emitted upon completion of the child.
  17  *
  18  * The child process is not killed when the Forkedcall instance goes out of
  19  * scope, but it can be killed by an explicit invocation of the kill() member
  20  * function.
  21  */
  22
  23 #include <config.h>
  24
  25 #ifdef __GNUG__
  26 #pragma implementation
  27 #endif
  28
  29 #include "forkedcall.h"
  30 #include "forkedcontr.h"
  31 #include "lstrings.h"
  32 #include "lyxlib.h"
  33 #include "filetools.h"
  34 #include "os.h"
  35 #include "debug.h"
  36 #include "frontends/Timeout.h"
  37
  38 #include <boost/bind.hpp>
  39
  40 #include <cerrno>
  41 #include <sys/types.h>
  42 #include <sys/wait.h>
  43 #include <csignal>
  44 #include <cstdlib>
  45 #include <unistd.h>
  46
  47 using std::endl;
  48
  49 #ifndef CXX_GLOBAL_CSTD
  50 using std::strerror;
  51 #endif
  52
  53
  54 Forkedcall::Forkedcall()
  55         : pid_(0), retval_(0)
  56 {}
  57
  58
  59 int Forkedcall::startscript(Starttype wait, string const & what)
  60 {
  61         if (wait == Wait) {
  62                 command_ = what;
  63                 retval_  = 0;
  64
  65                 pid_ = generateChild();
  66                 if (pid_ <= 0) { // child or fork failed.
  67                         retval_ = 1;
  68                 } else {
  69                         retval_ = waitForChild();
  70                 }
  71
  72                 return retval_;
  73         }
  74
  75         // DontWait
  76         retval_ = startscript(what, SignalTypePtr());
  77         return retval_;
  78 }
  79
  80
  81 int Forkedcall::startscript(string const & what, SignalTypePtr signal)
  82 {
  83         command_ = what;
  84         signal_  = signal;
  85         retval_  = 0;
  86
  87         pid_ = generateChild();
  88         if (pid_ <= 0) { // child or fork failed.
  89                 retval_ = 1;
  90                 return retval_;
  91         }
  92
  93         // Non-blocking execution.
  94         // Integrate into the Controller
  95         ForkedcallsController & contr = ForkedcallsController::get();
  96         contr.addCall(*this);
  97
  98         return retval_;
  99 }
 100
 101
 102 void Forkedcall::emitSignal()
 103 {
 104         if (signal_.get()) {
 105                 signal_->operator()(command_, pid_, retval_);
 106         }
 107 }
 108
 109
 110 namespace {
 111
 112 class Murder : public boost::signals::trackable {
 113 public:
 114         //
 115         static void killItDead(int secs, pid_t pid)
 116         {
 117                 if (secs > 0) {
 118                         new Murder(secs, pid);
 119                 } else if (pid != 0) {
 120                         lyx::kill(pid, SIGKILL);
 121                 }
 122         }
 123
 124         //
 125         void kill()
 126         {
 127                 if (pid_ != 0) {
 128                         lyx::kill(pid_, SIGKILL);
 129                 }
 130                 lyxerr << "Killed " << pid_ << std::endl;
 131                 delete this;
 132         }
 133
 134 private:
 135         //
 136         Murder(int secs, pid_t pid)
 137                 : timeout_(0), pid_(pid)
 138         {
 139                 timeout_ = new Timeout(1000*secs, Timeout::ONETIME);
 140                 timeout_->timeout.connect(boost::bind(&Murder::kill, this));
 141                 timeout_->start();
 142         }
 143
 144         //
 145         ~Murder()
 146         {
 147                 delete timeout_;
 148         }
 149         //
 150         Timeout * timeout_;
 151         //
 152         pid_t pid_;
 153 };
 154
 155 } // namespace anon
 156
 157
 158 void Forkedcall::kill(int tol)
 159 {
 160         lyxerr << "Forkedcall::kill(" << tol << ")" << std::endl;
 161         if (pid() == 0) {
 162                 lyxerr << "Can't kill non-existent process!" << endl;
 163                 return;
 164         }
 165
 166         int const tolerance = std::max(0, tol);
 167         if (tolerance == 0) {
 168                 // Kill it dead NOW!
 169                 Murder::killItDead(0, pid());
 170
 171         } else {
 172                 int ret = lyx::kill(pid(), SIGHUP);
 173
 174                 // The process is already dead if wait_for_death is false
 175                 bool const wait_for_death = (ret == 0 && errno != ESRCH);
 176
 177                 if (wait_for_death) {
 178                         Murder::killItDead(tolerance, pid());
 179                 }
 180         }
 181 }
 182
 183
 184 // Wait for child process to finish. Returns returncode from child.
 185 int Forkedcall::waitForChild() {
 186         // We'll pretend that the child returns 1 on all error conditions.
 187         retval_ = 1;
 188         int status;
 189         bool wait = true;
 190         while (wait) {
 191                 pid_t waitrpid = waitpid(pid_, &status, WUNTRACED);
 192                 if (waitrpid == -1) {
 193                         lyxerr << "LyX: Error waiting for child:"
 194                                << strerror(errno) << endl;
 195                         wait = false;
 196                 } else if (WIFEXITED(status)) {
 197                         // Child exited normally. Update return value.
 198                         retval_ = WEXITSTATUS(status);
 199                         wait = false;
 200                 } else if (WIFSIGNALED(status)) {
 201                         lyxerr << "LyX: Child didn't catch signal "
 202                                << WTERMSIG(status)
 203                                << "and died. Too bad." << endl;
 204                         wait = false;
 205                 } else if (WIFSTOPPED(status)) {
 206                         lyxerr << "LyX: Child (pid: " << pid_
 207                                << ") stopped on signal "
 208                                << WSTOPSIG(status)
 209                                << ". Waiting for child to finish." << endl;
 210                 } else {
 211                         lyxerr << "LyX: Something rotten happened while "
 212                                 "waiting for child " << pid_ << endl;
 213                         wait = false;
 214                 }
 215         }
 216         return retval_;
 217 }
 218
 219
 220 // generate child in background
 221 pid_t Forkedcall::generateChild()
 222 {
 223         const int MAX_ARGV = 255;
 224         char *syscmd = 0;
 225         char *argv[MAX_ARGV];
 226
 227         string childcommand(command_); // copy
 228         bool more = true;
 229         string rest = split(command_, childcommand, ' ');
 230
 231         int  index = 0;
 232         while (more) {
 233                 childcommand = frontStrip(childcommand);
 234                 if (syscmd == 0) {
 235                         syscmd = new char[childcommand.length() + 1];
 236                         childcommand.copy(syscmd, childcommand.length());
 237                         syscmd[childcommand.length()] = '\0';
 238                 }
 239                 if (!childcommand.empty()) {
 240                         char * tmp = new char[childcommand.length() + 1];
 241                         childcommand.copy(tmp, childcommand.length());
 242                         tmp[childcommand.length()] = '\0';
 243                         argv[index++] = tmp;
 244                 }
 245
 246                 // reinit
 247                 more = !rest.empty();
 248                 if (more)
 249                         rest = split(rest, childcommand, ' ');
 250         }
 251         argv[index] = 0;
 252
 253 #ifndef __EMX__
 254         pid_t cpid = ::fork();
 255         if (cpid == 0) { // child
 256                 execvp(syscmd, argv);
 257                 // If something goes wrong, we end up here:
 258                 lyxerr << "execvp failed: "
 259                        << strerror(errno) << endl;
 260         }
 261 #else
 262         pid_t cpid = spawnvp(P_SESSION|P_DEFAULT|P_MINIMIZE|P_BACKGROUND,
 263                              syscmd, argv);
 264 #endif
 265
 266         if (cpid < 0) { // error
 267                 lyxerr << "Could not fork: "
 268                        << strerror(errno) << endl;
 269         }
 270
 271         return cpid;
 272 }