627 lines
17 KiB
C++
627 lines
17 KiB
C++
/* cygload.cc
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Written by Max Kaehn <slothman@electric-cloud.com>
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for details.
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Note that dynamically linking to cygwin1.dll automatically places your code
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under the GPL unless you purchase a Cygwin Contract with Red Hat, Inc.
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See http://www.redhat.com/software/cygwin/ for more information.
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cygload demonstrates how to dynamically load cygwin1.dll. The default
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build uses MinGW to compile it; the Makefile also shows how to build
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it using the Microsoft compiler.
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By default, the program will silently test basic functionality:
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* Making space on the stack for cygtls
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* Loading and initializing cygwin1.dll
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* Path translation
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* Error handling
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* Signal handling
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Options for this program:
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-v Verbose output. Normal operation is entirely silent,
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save for errors.
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-testinterrupts Pauses the program for 30 seconds so you can demonstrate
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that it handles ^C properly.
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-cygwin Name of DLL to load. Defaults to "cygwin1.dll". */
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#include "cygload.h"
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#include <iostream>
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#include <sstream>
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#include <vector>
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#include <errno.h> // for ENOENT
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#include <sys/types.h>
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#include <sys/stat.h>
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using std::cout;
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using std::cerr;
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using std::endl;
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using std::string;
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cygwin::padding *cygwin::padding::_main = NULL;
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DWORD cygwin::padding::_mainTID = 0;
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// A few cygwin constants.
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static const int SIGHUP = 1;
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static const int SIGINT = 2;
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static const int SIGTERM = 15; // Cygwin won't deliver this one to us;
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// expect unadorned "kill" to just kill
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// your process.
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static const int SIGSTOP = 17; // Cygwin insists on delivering SIGSTOP to
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// the main thread. If your main thread
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// is not interruptible, you'll miss the
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// signal and ignore the request to suspend.
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static const int SIGTSTP = 18; // ^Z on a tty.
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static const int SIGCONT = 19; // Resume a stopped process.
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static const int SIGUSR1 = 30;
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static const int SIGUSR2 = 31;
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// Using *out instead of cout. In verbose mode, out == &cout.
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static std::ostream *out = NULL;
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cygwin::padding::padding ()
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{
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_main = this;
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_mainTID = GetCurrentThreadId ();
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_end = _padding + sizeof (_padding);
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char *stackbase;
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#ifdef __GNUC__
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__asm__ (
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"movl %%fs:4, %0"
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:"=r"(stackbase)
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);
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#else
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__asm
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{
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mov eax, fs:[4];
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mov stackbase, eax;
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}
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#endif
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_stackbase = stackbase;
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// We've gotten as close as we can to the top of the stack. Even
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// subverting the entry point, though, still doesn't get us there-- I'm
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// getting 64 bytes in use before the entry point. So we back up the data
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// there and restore it when the destructor is called:
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if ((_stackbase - _end) != 0)
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{
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size_t delta = (_stackbase - _end);
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_backup.resize (delta);
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memcpy (&(_backup[0]), _end, delta);
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}
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}
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cygwin::padding::~padding ()
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{
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_main = NULL;
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if (_backup.size ())
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{
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memcpy (_end, &(_backup[0]), _backup.size ());
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}
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}
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void
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cygwin::padding::check ()
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{
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if (_main == NULL)
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throw std::runtime_error ("No padding declared!");
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if (_mainTID != GetCurrentThreadId ())
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throw std::runtime_error ("You need to initialize cygwin::connector "
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"in the same thread in which you declared the "
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"padding.");
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if (_main->_backup.size ())
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*out << "Warning! Stack base is "
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<< static_cast<void *>(_main->_stackbase)
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<< ". padding ends at " << static_cast<void *>(_main->_end)
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<< ". Delta is " << (_main->_stackbase - _main->_end)
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<< ". Stack variables could be overwritten!" << endl;
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}
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cygwin::connector::connector (const char *dll)
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{
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// This will throw if padding is not in place.
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padding::check ();
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*out << "Loading " << dll << "..." << endl;
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// This should call init.cc:dll_entry() with DLL_PROCESS_ATTACH,
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// which calls dll_crt0_0().
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if ((_library = LoadLibrary (dll)) == NULL)
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throw windows_error ("LoadLibrary", dll);
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*out << "Initializing cygwin..." << endl;
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// This calls dcrt0.cc:cygwin_dll_init(), which calls dll_crt0_1(),
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// which will, among other things:
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// * spawn the cygwin signal handling thread from sigproc_init()
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// * initialize the thread-local storage for this thread and overwrite
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// the first 4K of the stack
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void (*cyginit) ();
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get_symbol ("cygwin_dll_init", cyginit);
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(*cyginit) ();
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*out << "Loading symbols..." << endl;
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// Pick up the function pointers for the basic infrastructure.
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get_symbol ("__errno", _errno);
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get_symbol ("strerror", _strerror);
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get_symbol ("cygwin_conv_to_full_posix_path", _conv_to_full_posix_path);
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get_symbol ("cygwin_conv_to_full_win32_path", _conv_to_full_win32_path);
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// Note that you need to be running an interruptible cygwin function if
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// you want to receive signals. You can use the standard signal()
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// mechanism if you're willing to have your main thread spend all its time
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// in interruptible cygwin functions like sleep(). Christopher Faylor
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// cautions that this solution "could be slightly racy": if a second
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// signal comes in before the first one is done processing, the thread
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// won't be back in sigwait() to catch it.
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*out << "Spawning signal handling thread..." << endl;
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_waiting_for_signals = true;
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_signal_thread_done = false;
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InitializeCriticalSection (&_thread_mutex);
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DWORD tid;
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_signal_thread = CreateThread (NULL, // Default security.
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32768, // Adjust the stack size as
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// appropriate for what your signal
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// handler needs in order to run, and
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// then add 4K for cygtls.
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&signal_thread, // Function to call
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this, // Context
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0, // Flags
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&tid); // Thread ID
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if (_signal_thread == NULL)
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throw windows_error ("CreateThread", "signal_thread");
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}
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cygwin::connector::~connector ()
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{
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try
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{
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// First, shut down signal handling.
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int (*raze) (int);
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int (*pthread_join) (void *, void **);
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get_symbol ("raise", raze);
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get_symbol ("pthread_join", pthread_join);
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// Tell the listener to shut down...
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_waiting_for_signals = false;
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int err = 0;
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EnterCriticalSection (&_thread_mutex);
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if (!_signal_thread_done)
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err = raze (SIGUSR2);
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LeaveCriticalSection (&_thread_mutex);
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if (err)
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cerr << error (this, "raise", "SIGUSR2").what () << endl;
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// ...and get the thread to join.
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if (!CloseHandle (_signal_thread))
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throw windows_error ("CloseHandle", "signal_thread");
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// This should call init.cc:dll_entry() with DLL_PROCESS_DETACH.
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if (!FreeLibrary (_library))
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throw windows_error ("FreeLibrary", "cygwin1.dll");
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}
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catch (std::exception &x)
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{
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cerr << x.what () << endl;
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}
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}
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DWORD WINAPI
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cygwin::connector::signal_thread (void *param)
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{
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connector *that = reinterpret_cast < connector * > (param);
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try
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{
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that->await_signal ();
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}
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catch (std::exception &x)
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{
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cerr << "signal_thread caught " << x.what () << endl;
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return 0;
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}
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return 0;
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}
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void
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cygwin::connector::await_signal ()
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{
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// Wait for signals.
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unsigned long sigset[32];
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int sig;
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int (*empty) (void *);
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int (*add) (void *, int);
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int (*wait) (void *, int *);
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get_symbol ("sigemptyset", empty);
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get_symbol ("sigaddset", add);
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get_symbol ("sigwait", wait);
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empty (sigset);
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add (sigset, SIGHUP);
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add (sigset, SIGINT);
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// add (sigset, SIGSTOP);
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// add (sigset, SIGTSTP); // I can't get this to suspend properly, so
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// I'll leave it up to chance that the main
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// thread is interruptible.
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add (sigset, SIGUSR1);
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add (sigset, SIGUSR2);
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while (_waiting_for_signals)
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{
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int err = wait (sigset, &sig);
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if (err)
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cerr << error (this, "sigwait").what () << endl;
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else
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*out << "Received signal " << sig << "." << endl;
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switch (sig)
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{
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case SIGUSR2:
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if (!_waiting_for_signals)
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{
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// SIGUSR2 is how ~connector wakes this thread
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goto done;
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}
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break;
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default:
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break;
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}
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handle_signals (sig);
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}
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done:
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EnterCriticalSection (&_thread_mutex);
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_signal_thread_done = true;
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LeaveCriticalSection (&_thread_mutex);
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*out << "await_signal done." << endl;
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}
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cygwin::connector::signal_handler *
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cygwin::connector::set_handler (int signal, signal_handler *handler)
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{
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signal_handler *retval = _signal_handlers[signal];
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if (handler == NULL)
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_signal_handlers.erase (signal);
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else
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_signal_handlers[signal] = handler;
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return retval;
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}
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void
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cygwin::connector::handle_signals (int sig)
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{
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callback_list::iterator h = _signal_handlers.find (sig);
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if (h != _signal_handlers.end ())
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{
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try
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{
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signal_handler *handler = h->second;
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(*handler) (sig);
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return;
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}
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catch (std::exception &x)
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{
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cerr << "cygwin::connector::handle_signals caught "
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<< x.what () << "!" << endl;
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return;
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}
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}
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cerr << "No handler for signal " << sig << "!" << endl;
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}
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int
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cygwin::connector::err_no () const
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{
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int *e = (*_errno) ();
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if (e == NULL)
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{
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return -1;
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}
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return *e;
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}
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string
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cygwin::connector::str_error (int err_no) const
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{
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string retval;
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const char *s = (*_strerror) (err_no);
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if (s != NULL)
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{
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retval = s;
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}
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else
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{
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std::ostringstream o;
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o << "Unexpected errno " << err_no;
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retval = o.str ();
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}
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return retval;
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}
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string
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cygwin::connector::unix_path (const string &windows) const
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{
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char buf[MAX_PATH];
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_conv_to_full_posix_path (windows.c_str (), buf);
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return string (buf);
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}
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string
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cygwin::connector::win_path (const string &unix) const
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{
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char buf[MAX_PATH];
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_conv_to_full_win32_path (unix.c_str (), buf);
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return string (buf);
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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string
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cygwin::error::format (cygwin::connector *c,
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int err_no, const char *message, const char *detail)
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{
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std::ostringstream ret;
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ret << message;
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if (detail)
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{
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ret << "(" << detail << ")";
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}
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ret << ": " << c->str_error (err_no);
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return ret.str ();
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}
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string
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windows_error::format (DWORD error, const char *message, const char *detail)
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{
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std::ostringstream ret;
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char buf[512];
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DWORD bytes;
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ret << message;
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if (detail)
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ret << "(" << detail << ")";
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ret << ": ";
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bytes = FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM, 0, error,
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MAKELANGID (LANG_NEUTRAL, SUBLANG_DEFAULT),
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buf, sizeof (buf), 0);
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if (bytes == 0)
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ret << "Unexpected Windows error " << error;
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else
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{
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// Remove trailing whitespace
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char *p = buf + bytes - 1;
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while (isspace (*p))
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*p-- = '\0';
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ret << buf << " (" << error << ")";
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}
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return ret.str ();
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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extern "C" int mainCRTStartup ();
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// This just pushes 4K onto the stack, backs up the original stack, and
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// jumps into the regular startup code. This avoids having to worry about
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// backing up argc and argv.
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extern "C" int __stdcall
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cygloadCRTStartup ()
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{
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cygwin::padding padding;
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return mainCRTStartup ();
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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static void
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hangup (int sig)
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{
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cout << "Hangup (" << sig << ")." << endl;
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}
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static void
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interrupt (int sig)
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{
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cerr << "Interrupt (" << sig << ")!" << endl;
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exit (0);
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}
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static int caught = false;
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static void
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catch_signal (int)
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{
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*out << "Signals are working." << endl;
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caught = true;
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}
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int
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main (int argc, char *argv[])
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{
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// If you do not want to use cygloadCRTStartup() as an entry point,
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// uncomment this line, but be sure to have *everything* you want
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// from the stack below it backed up before you call the
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// constructor for cygwin::connector.
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//cygwin::padding padding;
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std::ostringstream output;
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bool verbose = false, testinterrupts = false;
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const char *dll = "cygwin1.dll";
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out = &output;
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for (int i = 1; i < argc; ++i)
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{
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string arg = string (argv[i]);
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if (arg == "-v")
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{
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verbose = true;
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out = &cout;
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}
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else if (arg == "-testinterrupts")
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testinterrupts = true;
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else if (arg == "-cygwin")
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{
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if (i+1 >= argc)
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{
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cerr << "Need to supply an argument with -cygwin." << endl;
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return 255;
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}
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dll = argv[++i];
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}
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}
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try
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{
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*out << "Connecting to cygwin..." << endl;
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cygwin::connector cygwin (dll);
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*out << "Successfully connected." << endl;
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string result = cygwin.str_error (ENOENT);
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if (result != "No such file or directory")
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{
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cerr << "strerror(ENOENT) returned \""
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<< result
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<< "\" instead of \"No such file or directory\"!"
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<< endl;
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return 1;
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}
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else if (verbose)
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{
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*out << "strerror(ENOENT) = " << result << endl;
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}
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// Path conversion: from cygwin to Windows...
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result = cygwin.win_path ("/usr");
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struct _stat statbuf;
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if (::_stat (result.c_str (), &statbuf) < 0)
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{
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cerr << "stat(\"" << result << "\") failed!" << endl;
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return 2;
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}
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else if (verbose)
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{
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*out << "/usr == " << result << endl;
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}
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// ...and back:
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char buf[MAX_PATH], scratch[256];
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GetSystemDirectory (buf, sizeof(buf));
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int (*cygstat) (const char *, void *);
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cygwin.get_symbol ("stat", cygstat);
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if (cygstat (buf, scratch) < 0)
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{
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cerr << "cygwin stat(\"" << buf << "\") failed!" << endl;
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return 3;
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}
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else if (verbose)
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{
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*out << buf << " == " << cygwin.unix_path(buf) << endl;
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}
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// Test error handling. This should output
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// "open(/potrzebie/furshlugginer): No such file or directory"
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{
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int (*cygopen) (const char *, int);
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cygwin.get_symbol ("open", cygopen);
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if (cygopen ("/potrzebie/furshlugginer", 0 /* O_RDONLY */ ) < 0)
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{
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int err = cygwin.err_no ();
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if (err != ENOENT)
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{
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cerr << "cygwin open(\"/potrzebie/furshlugginer\", "
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"O_RDONLY): expected to fail with ENOENT, got "
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<< err << "!" << endl;
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return 4;
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}
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if (verbose)
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*out << cygwin::error (&cygwin, "open",
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"/potrzebie/furshlugginer").what ()
|
|
<< endl;
|
|
}
|
|
else
|
|
{
|
|
cerr << "/potrzebie/furshlugginer should not exist!"
|
|
<< endl;
|
|
return 5;
|
|
}
|
|
}
|
|
|
|
// And signal handling:
|
|
std::pointer_to_unary_function < int , void > h1 (&hangup);
|
|
std::pointer_to_unary_function < int , void > h2 (&interrupt);
|
|
std::pointer_to_unary_function < int , void > h3 (&catch_signal);
|
|
cygwin.set_handler (SIGHUP, &h1);
|
|
cygwin.set_handler (SIGINT, &h2);
|
|
cygwin.set_handler (SIGUSR1, &h3);
|
|
|
|
// Make sure the signal handler thread has had time to start...
|
|
Sleep (100);
|
|
// Send a test signal to set "caught" to true...
|
|
int (*raze) (int);
|
|
cygwin.get_symbol ("raise", raze);
|
|
raze (SIGUSR1);
|
|
// And give the thread time to wait for the shutdown signal.
|
|
Sleep (100);
|
|
|
|
if (testinterrupts)
|
|
{
|
|
// This is a worst case scenario for testing interrupts: the
|
|
// main thread is in a long-duration Windows API call. This
|
|
// makes the main thread uninterruptible; cygwin will retry
|
|
// 20 times, with a low_priority_sleep(0) between each try.
|
|
cout << "Sleeping for 30 seconds, waiting for a signal..." << endl;
|
|
Sleep (30000);
|
|
cout << "Done waiting." << endl;
|
|
}
|
|
}
|
|
catch (std::exception &x)
|
|
{
|
|
cerr << x.what () << endl;
|
|
return 2;
|
|
}
|
|
|
|
if (caught)
|
|
return 0;
|
|
else
|
|
{
|
|
cerr << "Never received SIGUSR1." << endl;
|
|
return 1;
|
|
}
|
|
}
|