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 <cerrno>
  39 #include <sys/types.h>
  40 #include <sys/wait.h>
  41 #include <csignal>
  42 #include <cstdlib>
  43 #include <unistd.h>
  44
  45 using std::endl;
  46
  47 #ifndef CXX_GLOBAL_CSTD
  48 using std::strerror;
  49 #endif
  50
  51
  52 Forkedcall::Forkedcall()
  53         : pid_(0), retval_(0)
  54 {}
  55
  56
  57 int Forkedcall::startscript(Starttype wait, string const & what)
  58 {
  59         if (wait == Wait) {
  60                 command_ = what;
  61                 retval_  = 0;
  62
  63                 pid_ = generateChild();
  64                 if (pid_ <= 0) { // child or fork failed.
  65                         retval_ = 1;
  66                 } else {
  67                         retval_ = waitForChild();
  68                 }
  69
  70                 return retval_;
  71         }
  72
  73         // DontWait
  74         retval_ = startscript(what, SignalTypePtr());
  75         return retval_;
  76 }
  77
  78
  79 int Forkedcall::startscript(string const & what, SignalTypePtr signal)
  80 {
  81         command_ = what;
  82         signal_  = signal;
  83         retval_  = 0;
  84
  85         pid_ = generateChild();
  86         if (pid_ <= 0) { // child or fork failed.
  87                 retval_ = 1;
  88                 return retval_;
  89         }
  90
  91         // Non-blocking execution.
  92         // Integrate into the Controller
  93         ForkedcallsController & contr = ForkedcallsController::get();
  94         contr.addCall(*this);
  95
  96         return retval_;
  97 }
  98
  99
 100 void Forkedcall::emitSignal()
 101 {
 102         if (signal_.get()) {
 103                 signal_->emit(command_, pid_, retval_);
 104         }
 105 }
 106
 107
 108 namespace {
 109
 110 class Murder : public SigC::Object {
 111 public:
 112         //
 113         static void killItDead(int secs, pid_t pid)
 114         {
 115                 if (secs > 0) {
 116                         new Murder(secs, pid);
 117                 } else if (pid != 0) {
 118                         lyx::kill(pid, SIGKILL);
 119                 }
 120         }
 121
 122         //
 123         void kill()
 124         {
 125                 if (pid_ != 0) {
 126                         lyx::kill(pid_, SIGKILL);
 127                 }
 128                 lyxerr << "Killed " << pid_ << std::endl;
 129                 delete this;
 130         }
 131
 132 private:
 133         //
 134         Murder(int secs, pid_t pid)
 135                 : timeout_(0), pid_(pid)
 136         {
 137                 timeout_ = new Timeout(1000*secs, Timeout::ONETIME);
 138                 timeout_->timeout.connect(SigC::slot(this, &Murder::kill));
 139                 timeout_->start();
 140         }
 141
 142         //
 143         ~Murder()
 144         {
 145                 delete timeout_;
 146         }
 147         //
 148         Timeout * timeout_;
 149         //
 150         pid_t pid_;
 151 };
 152
 153 } // namespace anon
 154
 155
 156 void Forkedcall::kill(int tol)
 157 {
 158         lyxerr << "Forkedcall::kill(" << tol << ")" << std::endl;
 159         if (pid() == 0) {
 160                 lyxerr << "Can't kill non-existent process!" << endl;
 161                 return;
 162         }
 163
 164         int const tolerance = std::max(0, tol);
 165         if (tolerance == 0) {
 166                 // Kill it dead NOW!
 167                 Murder::killItDead(0, pid());
 168
 169         } else {
 170                 int ret = lyx::kill(pid(), SIGHUP);
 171
 172                 // The process is already dead if wait_for_death is false
 173                 bool const wait_for_death = (ret == 0 && errno != ESRCH);
 174
 175                 if (wait_for_death) {
 176                         Murder::killItDead(tolerance, pid());
 177                 }
 178         }
 179 }
 180
 181
 182 // Wait for child process to finish. Returns returncode from child.
 183 int Forkedcall::waitForChild() {
 184         // We'll pretend that the child returns 1 on all error conditions.
 185         retval_ = 1;
 186         int status;
 187         bool wait = true;
 188         while (wait) {
 189                 pid_t waitrpid = waitpid(pid_, &status, WUNTRACED);
 190                 if (waitrpid == -1) {
 191                         lyxerr << "LyX: Error waiting for child:"
 192                                << strerror(errno) << endl;
 193                         wait = false;
 194                 } else if (WIFEXITED(status)) {
 195                         // Child exited normally. Update return value.
 196                         retval_ = WEXITSTATUS(status);
 197                         wait = false;
 198                 } else if (WIFSIGNALED(status)) {
 199                         lyxerr << "LyX: Child didn't catch signal "
 200                                << WTERMSIG(status)
 201                                << "and died. Too bad." << endl;
 202                         wait = false;
 203                 } else if (WIFSTOPPED(status)) {
 204                         lyxerr << "LyX: Child (pid: " << pid_
 205                                << ") stopped on signal "
 206                                << WSTOPSIG(status)
 207                                << ". Waiting for child to finish." << endl;
 208                 } else {
 209                         lyxerr << "LyX: Something rotten happened while "
 210                                 "waiting for child " << pid_ << endl;
 211                         wait = false;
 212                 }
 213         }
 214         return retval_;
 215 }
 216
 217
 218 // generate child in background
 219 pid_t Forkedcall::generateChild()
 220 {
 221         const int MAX_ARGV = 255;
 222         char *syscmd = 0;
 223         char *argv[MAX_ARGV];
 224
 225         string childcommand(command_); // copy
 226         bool more = true;
 227         string rest = split(command_, childcommand, ' ');
 228
 229         int  index = 0;
 230         while (more) {
 231                 childcommand = frontStrip(childcommand);
 232                 if (syscmd == 0) {
 233                         syscmd = new char[childcommand.length() + 1];
 234                         childcommand.copy(syscmd, childcommand.length());
 235                         syscmd[childcommand.length()] = '\0';
 236                 }
 237                 if (!childcommand.empty()) {
 238                         char * tmp = new char[childcommand.length() + 1];
 239                         childcommand.copy(tmp, childcommand.length());
 240                         tmp[childcommand.length()] = '\0';
 241                         argv[index++] = tmp;
 242                 }
 243
 244                 // reinit
 245                 more = !rest.empty();
 246                 if (more)
 247                         rest = split(rest, childcommand, ' ');
 248         }
 249         argv[index] = 0;
 250
 251 #ifndef __EMX__
 252         pid_t cpid = ::fork();
 253         if (cpid == 0) { // child
 254                 execvp(syscmd, argv);
 255                 // If something goes wrong, we end up here:
 256                 lyxerr << "execvp failed: "
 257                        << strerror(errno) << endl;
 258         }
 259 #else
 260         pid_t cpid = spawnvp(P_SESSION|P_DEFAULT|P_MINIMIZE|P_BACKGROUND,
 261                              syscmd, argv);
 262 #endif
 263
 264         if (cpid < 0) { // error
 265                 lyxerr << "Could not fork: "
 266                        << strerror(errno) << endl;
 267         }
 268
 269         return cpid;
 270 }