Sigaction and porting Linux code to Windows

Question

I am trying to port caffe (developed for Linux) source code to Windows environment. The problem is at sigaction structure at signal_handler.cpp and signal_handler.h. The source codes are shown below. My query is which library or code replacement can be done to make this sigaction works in Windows.

///Header file

#ifndef INCLUDE_CAFFE_UTIL_SIGNAL_HANDLER_H_
#define INCLUDE_CAFFE_UTIL_SIGNAL_HANDLER_H_

#include "caffe/proto/caffe.pb.h"
#include "caffe/solver.hpp"

namespace caffe {

class SignalHandler {
 public:
  // Contructor. Specify what action to take when a signal is received.
  SignalHandler(SolverAction::Enum SIGINT_action,
                SolverAction::Enum SIGHUP_action);
  ~SignalHandler();
  ActionCallback GetActionFunction();
 private:
  SolverAction::Enum CheckForSignals() const;
  SolverAction::Enum SIGINT_action_;
  SolverAction::Enum SIGHUP_action_;
};

}  // namespace caffe

#endif  // INCLUDE_CAFFE_UTIL_SIGNAL_HANDLER_H_

///Source file

    #include <boost/bind.hpp>
    #include <glog/logging.h>

    #include <signal.h>
    #include <csignal>

    #include "caffe/util/signal_handler.h"

    namespace {
      static volatile sig_atomic_t got_sigint = false;
      static volatile sig_atomic_t got_sighup = false;
      static bool already_hooked_up = false;

      void handle_signal(int signal) {
        switch (signal) {
        case SIGHUP:
          got_sighup = true;
          break;
        case SIGINT:
          got_sigint = true;
          break;
        }
      }

      void HookupHandler() {
        if (already_hooked_up) {
          LOG(FATAL) << "Tried to hookup signal handlers more than once.";
        }
        already_hooked_up = true;

        struct sigaction sa;
        // Setup the handler
        sa.sa_handler = &handle_signal;
        // Restart the system call, if at all possible
        sa.sa_flags = SA_RESTART;
        // Block every signal during the handler
        sigfillset(&sa.sa_mask);
        // Intercept SIGHUP and SIGINT
        if (sigaction(SIGHUP, &sa, NULL) == -1) {
          LOG(FATAL) << "Cannot install SIGHUP handler.";
        }
        if (sigaction(SIGINT, &sa, NULL) == -1) {
          LOG(FATAL) << "Cannot install SIGINT handler.";
        }
      }

      // Set the signal handlers to the default.
      void UnhookHandler() {
        if (already_hooked_up) {
          struct sigaction sa;
          // Setup the sighub handler
          sa.sa_handler = SIG_DFL;
          // Restart the system call, if at all possible
          sa.sa_flags = SA_RESTART;
          // Block every signal during the handler
          sigfillset(&sa.sa_mask);
          // Intercept SIGHUP and SIGINT
          if (sigaction(SIGHUP, &sa, NULL) == -1) {
            LOG(FATAL) << "Cannot uninstall SIGHUP handler.";
          }
          if (sigaction(SIGINT, &sa, NULL) == -1) {
            LOG(FATAL) << "Cannot uninstall SIGINT handler.";
          }

          already_hooked_up = false;
        }
      }

      // Return true iff a SIGINT has been received since the last time this
      // function was called.
      bool GotSIGINT() {
        bool result = got_sigint;
        got_sigint = false;
        return result;
      }

      // Return true iff a SIGHUP has been received since the last time this
      // function was called.
      bool GotSIGHUP() {
        bool result = got_sighup;
        got_sighup = false;
        return result;
      }
    }  // namespace

    namespace caffe {

    SignalHandler::SignalHandler(SolverAction::Enum SIGINT_action,
                                 SolverAction::Enum SIGHUP_action):
      SIGINT_action_(SIGINT_action),
      SIGHUP_action_(SIGHUP_action) {
      HookupHandler();
    }

    SignalHandler::~SignalHandler() {
      UnhookHandler();
    }

    SolverAction::Enum SignalHandler::CheckForSignals() const {
      if (GotSIGHUP()) {
        return SIGHUP_action_;
      }
      if (GotSIGINT()) {
        return SIGINT_action_;
      }
      return SolverAction::NONE;
    }

    // Return the function that the solver can use to find out if a snapshot or
    // early exit is being requested.
    ActionCallback SignalHandler::GetActionFunction() {
      return boost::bind(&SignalHandler::CheckForSignals, this);
    }

    }  // namespace caffe

The errors are

.\src\caffe\util\signal_handler.cpp(39): error C2065: 'SIGHUP' : undeclared identifier
1>..\src\caffe\util\signal_handler.cpp(42): error C2514: '`anonymous-namespace'::HookupHandler::sigaction' : class has no constructors
1>          ..\src\caffe\util\signal_handler.cpp(31) : see declaration of '`anonymous-namespace'::HookupHandler::sigaction'
1>..\src\caffe\util\signal_handler.cpp(50): error C2079: 'sa' uses undefined struct '`anonymous-namespace'::UnhookHandler::sigaction'
1>..\src\caffe\util\signal_handler.cpp(52): error C2228: left of '.sa_handler' must have class/struct/union
1>          type is 'int'
1>..\src\caffe\util\signal_handler.cpp(54): error C2228: left of '.sa_flags' must have class/struct/union
1>          type is 'int'
1>..\src\caffe\util\signal_handler.cpp(54): error C2065: 'SA_RESTART' : undeclared identifier
1>..\src\caffe\util\signal_handler.cpp(56): error C2228: left of '.sa_mask' must have class/struct/union

Dinadinah

if still relevant, the following github repo ports Caffe to Windows: github.com/happynear/caffe-windows – Duiker

There is an ANSI C signal() function that probably handles the interrupts you want. The constants you want are in signal.h, or <csignal> in C++. – Methodist

Answer 1

sigaction is part of the UNIX signals API. Windows provides only signal, which doesn't support SIGHUP or any flags (such as SA_RESTART). However, the very basic support is still there, so the code should still work reasonably correctly if you use just signal (and not sigaction).

Amling

I can't replace sigaction. But can I replace the functionality, I mean the action supported by sigaction will be replaced with signal. Signal is provided in Windows. How do you think? – Dinadinah

Yeah current solution is just to comment out that sigaction functions as I don't have time to solve at the moment. Windows doesn't provide SIGHUP flag, I'll replace with a flag that Windows supports and useful. – Dinadinah

Answer 2

Based on @nneonneo:

void handle_signal(int signal) {
    switch (signal) {
#ifdef _WIN32
    case SIGTERM:
    case SIGABRT:
    case SIGBREAK:
#else
    case SIGHUP:
#endif
      got_sighup = true;
      break;
    case SIGINT:
      got_sigint = true;
      break;
    }
  }
void HookupHandler() {
    if (already_hooked_up) {
      LOG(FATAL) << "Tried to hookup signal handlers more than once.";
    }
    already_hooked_up = true;
#ifdef _WIN32
    signal(SIGINT, handle_signal);
    signal(SIGTERM, handle_signal);
    signal(SIGABRT, handle_signal);
#else
    struct sigaction sa;
    // Setup the handler
    sa.sa_handler = &handle_signal;
    // Restart the system call, if at all possible
    sa.sa_flags = SA_RESTART;
    // Block every signal during the handler
    sigfillset(&sa.sa_mask);
    // Intercept SIGHUP and SIGINT
    if (sigaction(SIGHUP, &sa, NULL) == -1) {
      LOG(FATAL) << "Cannot install SIGHUP handler.";
    }
    if (sigaction(SIGINT, &sa, NULL) == -1) {
      LOG(FATAL) << "Cannot install SIGINT handler.";
    }
#endif
  }
 void UnhookHandler() {
    if (already_hooked_up) {
#ifdef _WIN32
        signal(SIGINT, SIG_DFL);
        signal(SIGTERM, SIG_DFL);
        signal(SIGABRT, SIG_DFL);
#else
      struct sigaction sa;
      // Setup the sighub handler
      sa.sa_handler = SIG_DFL;
      // Restart the system call, if at all possible
      sa.sa_flags = SA_RESTART;
      // Block every signal during the handler
      sigfillset(&sa.sa_mask);
      // Intercept SIGHUP and SIGINT
      if (sigaction(SIGHUP, &sa, NULL) == -1) {
        LOG(FATAL) << "Cannot uninstall SIGHUP handler.";
      }
      if (sigaction(SIGINT, &sa, NULL) == -1) {
        LOG(FATAL) << "Cannot uninstall SIGINT handler.";
      }
#endif

      already_hooked_up = false;
    }
  }

Duiker