diff -r e3a32a79a10a -r 4355e72ffd47 src/crashcatcher.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/crashcatcher.cpp	Wed Oct 23 12:46:10 2013 +0300
@@ -0,0 +1,109 @@
+#ifdef __unix__
+
+#include <QString>
+#include <QProcess>
+#include <QTemporaryFile>
+#include <QMessageBox>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/prctl.h>
+#include "crashcatcher.h"
+#include "types.h"
+#include "dialogs.h"
+
+// Is the crash catcher active now?
+static bool g_crashCatcherActive = false;
+
+// If an assertion failed, what was it?
+static str g_assertionFailure;
+
+// List of signals to catch and crash on
+static QList<int> g_signalsToCatch ({
+	SIGSEGV, // segmentation fault
+	SIGABRT, // abort() calls
+	SIGFPE, // floating point exceptions (e.g. division by zero)
+	SIGILL, // illegal instructions
+});
+
+// =============================================================================
+// -----------------------------------------------------------------------------
+static void handleCrash (int sig)
+{	printf ("%s: crashed with signal %d, launching gdb\n", __func__, sig);
+
+	if (g_crashCatcherActive)
+	{	printf ("caught signal while crash catcher is active!\n");
+		exit (149);
+	}
+
+	const pid_t pid = getpid();
+	QProcess proc;
+	QTemporaryFile commandsFile;
+
+	g_crashCatcherActive = true;
+
+	if (commandsFile.open())
+	{	commandsFile.write (fmt ("attach %1\n", pid).toLocal8Bit());
+		commandsFile.write (str ("backtrace full\n").toLocal8Bit());
+		commandsFile.write (str ("detach\n").toLocal8Bit());
+		commandsFile.write (str ("quit").toLocal8Bit());
+		commandsFile.flush();
+		commandsFile.close();
+	}
+
+	QStringList args ({"-x", commandsFile.fileName()});
+
+	proc.start ("gdb", args);
+
+	// Linux doesn't allow ptrace to be used on anything but direct child processes
+	// so we need to use prctl to register an exception to this to allow GDB attach to us.
+	// We need to do this now and no earlier because only now we actually know GDB's PID.
+	prctl (PR_SET_PTRACER, proc.pid(), 0, 0, 0);
+
+	proc.waitForFinished (1000);
+	str output = QString (proc.readAllStandardOutput());
+	str err = QString (proc.readAllStandardError());
+
+	bombBox (fmt ("<h3>Program crashed with signal %1</h3>\n\n"
+		"%2"
+		"<p><b>GDB <tt>stdout</tt>:</b></p><pre>%3</pre>\n"
+		"<p><b>GDB <tt>stderr</tt>:</b></p><pre>%4</pre>",
+		sig, (!g_assertionFailure.isEmpty()) ? g_assertionFailure : "", output, err));
+}
+
+// =============================================================================
+// -----------------------------------------------------------------------------
+void initCrashCatcher()
+{	struct sigaction sighandler;
+	sighandler.sa_handler = &handleCrash;
+	sighandler.sa_flags = 0;
+	sigemptyset (&sighandler.sa_mask);
+
+	for (int sig : g_signalsToCatch)
+		sigaction (sig, &sighandler, null);
+
+	log ("%1: crash catcher hooked to signals: %2\n", __func__, g_signalsToCatch);
+}
+#endif // #ifdef __unix__
+
+// =============================================================================
+// This function must be readily available in both Windows and Linux. We display
+// the bomb box straight in Windows while in Linux we let abort() trigger the
+// signal handler, which will cause the usual bomb box with GDB diagnostics.
+// Said prompt will embed the assertion failure information.
+// -----------------------------------------------------------------------------
+void assertionFailure (const char* file, int line, const char* funcname, const char* expr)
+{	str errmsg = fmt (
+		"<p><b>File</b>: <tt>%1</tt><br />"
+		"<b>Line</b>: <tt>%2</tt><br />"
+		"<b>Function:</b> <tt>%3</tt></p>"
+		"<p>Assertion <b><tt>`%4'</tt></b> failed.</p>",
+		file, line, funcname, expr);
+
+	g_assertionFailure = errmsg;
+
+#ifndef __unix__
+	bombBox (errmsg);
+#endif
+
+	abort();
+}
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