diff --git a/source.list b/source.list
--- a/source.list
+++ b/source.list
@@ -79,7 +79,11 @@ townname.cpp
 		#if OS2
 			os/os2/os2.cpp
 		#else
-			os/unix/crashlog_unix.cpp
+			#if OSX
+				os/macosx/crashlog_osx.cpp
+			#else
+				os/unix/crashlog_unix.cpp
+			#end
 			os/unix/unix.cpp
 		#end
 	#end
diff --git a/src/os/macosx/crashlog_osx.cpp b/src/os/macosx/crashlog_osx.cpp
new file mode 100644
--- /dev/null
+++ b/src/os/macosx/crashlog_osx.cpp
@@ -0,0 +1,238 @@
+/* $Id$ */
+
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file crashlog_osx.cpp OS X crash log handler */
+
+#include "../../stdafx.h"
+#include "../../crashlog.h"
+#include "../../string_func.h"
+#include "../../gamelog.h"
+#include "macos.h"
+
+#include <errno.h>
+#include <signal.h>
+#include <mach-o/arch.h>
+#include <dlfcn.h>
+#include <cxxabi.h>
+
+
+/* Macro testing a stack address for valid alignment. */
+#if defined(__i386__)
+#define IS_ALIGNED(addr) (((uintptr_t)(addr) & 0xf) == 8)
+#else
+#define IS_ALIGNED(addr) (((uintptr_t)(addr) & 0xf) == 0)
+#endif
+
+/* printf format specification for 32/64-bit addresses. */
+#if __LP64__
+#define PRINTF_PTR "0x%016lx"
+#else
+#define PRINTF_PTR "0x%08lx"
+#endif
+
+#define MAX_STACK_FRAMES 64
+
+/**
+ * OSX implementation for the crash logger.
+ */
+class CrashLogOSX : public CrashLog {
+	/** Signal that has been thrown. */
+	int signum;
+
+	char filename_save[MAX_PATH];  ///< Path of crash.sav
+	char filename_log[MAX_PATH];   ///< Path of crash.log
+
+	/* virtual */ char *LogOSVersion(char *buffer, const char *last) const
+	{
+		int ver_maj, ver_min, ver_bug;
+		GetMacOSVersion(&ver_maj, &ver_min, &ver_bug);
+
+		const NXArchInfo *arch = NXGetLocalArchInfo();
+
+		return buffer + seprintf(buffer, last,
+				"Operating system:\n"
+				" Name:    Mac OS X\n"
+				" Release: %d.%d.%d\n"
+				" Machine: %s\n"
+				" Min Ver: %d\n\n",
+				ver_maj, ver_min, ver_bug,
+				arch != NULL ? arch->description : "unknown",
+				MAC_OS_X_VERSION_MIN_REQUIRED
+		);
+	}
+
+	/* virtual */ char *LogError(char *buffer, const char *last, const char *message) const
+	{
+		return buffer + seprintf(buffer, last,
+				"Crash reason:\n"
+				" Signal:  %s (%d)\n"
+				" Message: %s\n\n",
+				strsignal(this->signum),
+				this->signum,
+				message == NULL ? "<none>" : message
+		);
+	}
+
+	/* virtual */ char *LogStacktrace(char *buffer, const char *last) const
+	{
+		/* As backtrace() is only implemented in 10.5 or later,
+		 * we're rolling our own here. Mostly based on
+		 * http://stackoverflow.com/questions/289820/getting-the-current-stack-trace-on-mac-os-x
+		 * and some details looked up in the Darwin sources. */
+		buffer += seprintf(buffer, last, "\nStacktrace:\n");
+
+		void **frame;
+#if defined(__ppc__) || defined(__ppc64__)
+		/* Apple says __builtin_frame_address can be broken on PPC. */
+		__asm__ volatile("mr %0, r1" : "=r" (frame));
+#else
+		frame = (void **)__builtin_frame_address(0);
+#endif
+
+		for (int i = 0; frame != NULL && i < MAX_STACK_FRAMES; i++) {
+			/* Get IP for current stack frame. */
+#if defined(__ppc__) || defined(__ppc64__)
+			void *ip = frame[2];
+#else
+			void *ip = frame[1];
+#endif
+			if (ip == NULL) break;
+
+			/* Print running index. */
+			buffer += seprintf(buffer, last, " [%02d]", i);
+
+			Dl_info dli;
+			bool dl_valid = dladdr(ip, &dli) != 0;
+
+			const char *fname = "???";
+			if (dl_valid && dli.dli_fname) {
+				/* Valid image name? Extract filename from the complete path. */
+				const char *s = strrchr(dli.dli_fname, '/');
+				if (s != NULL) {
+					fname = s + 1;
+				} else {
+					fname = dli.dli_fname;
+				}
+			}
+			/* Print image name and IP. */
+			buffer += seprintf(buffer, last, " %-20s " PRINTF_PTR, fname, (uintptr_t)ip);
+
+			/* Print function offset if information is available. */
+			if (dl_valid && dli.dli_sname != NULL && dli.dli_saddr != NULL) {
+				/* Try to demangle a possible C++ symbol. */
+				int status = -1;
+				char *func_name = abi::__cxa_demangle(dli.dli_sname, NULL, 0, &status);
+
+				ptrdiff_t offset = (intptr_t)ip - (intptr_t)dli.dli_saddr;
+				buffer += seprintf(buffer, last, " (%s + %d)", func_name != NULL ? func_name : dli.dli_sname, offset);
+
+				free(func_name);
+			}
+			buffer += seprintf(buffer, last, "\n");
+
+			/* Get address of next stack frame. */
+			void **next = (void **)frame[0];
+			/* Frame address not increasing or not aligned? Broken stack, exit! */
+			if (next <= frame || !IS_ALIGNED(next)) break;
+			frame = next;
+		}
+
+		return buffer + seprintf(buffer, last, "\n");
+	}
+
+public:
+	/**
+	 * A crash log is always generated by signal.
+	 * @param signum the signal that was caused by the crash.
+	 */
+	CrashLogOSX(int signum) : signum(signum)
+	{
+		filename_log[0] = '\0';
+		filename_save[0] = '\0';
+	}
+
+	/** Generate the crash log. */
+	bool MakeCrashLog()
+	{
+		char buffer[65536];
+		bool ret = true;
+
+		printf("Crash encountered, generating crash log...\n");
+		this->FillCrashLog(buffer, lastof(buffer));
+		printf("%s\n", buffer);
+		printf("Crash log generated.\n\n");
+
+		printf("Writing crash log to disk...\n");
+		if (!this->WriteCrashLog(buffer, filename_log, lastof(filename_log))) {
+			filename_log[0] = '\0';
+			ret = false;
+		}
+
+		printf("Writing crash savegame...\n");
+		if (!this->WriteSavegame(filename_save, lastof(filename_save))) {
+			filename_save[0] = '\0';
+			ret = false;
+		}
+
+		return ret;
+	}
+
+	/** Show a dialog with the crash information. */
+	void DisplayCrashDialog() const
+	{
+		static const char crash_title[] =
+			"A serious fault condition occured in the game. The game will shut down.";
+		static const char crash_info[] =
+			"Please send the generated crash information and the last (auto)save to the developers. "
+			"This will greatly help debugging. The correct place to do this is http://bugs.openttd.org.\n\n"
+			"Generated file(s):\n%s\n%s";
+
+		char message[1024];
+		seprintf(message, lastof(message), crash_info, this->filename_log, this->filename_save);
+
+		ShowMacDialog(crash_title, message, "Quit");
+	}
+};
+
+/** The signals we want our crash handler to handle. */
+static const int _signals_to_handle[] = { SIGSEGV, SIGABRT, SIGFPE, SIGBUS, SIGILL, SIGSYS };
+
+/**
+ * Entry point for the crash handler.
+ * @note Not static so it shows up in the backtrace.
+ * @param signum the signal that caused us to crash.
+ */
+void CDECL HandleCrash(int signum)
+{
+	/* Disable all handling of signals by us, so we don't go into infinite loops. */
+	for (const int *i = _signals_to_handle; i != endof(_signals_to_handle); i++) {
+		signal(*i, SIG_DFL);
+	}
+
+	if (GamelogTestEmergency()) {
+		ShowMacDialog("A serious fault condition occured in the game. The game will shut down.",
+				"As you loaded an emergency savegame no crash information will be generated.\n",
+				"Quit");
+		abort();
+	}
+
+	CrashLogOSX log(signum);
+	log.MakeCrashLog();
+	log.DisplayCrashDialog();
+
+	CrashLog::AfterCrashLogCleanup();
+	abort();
+}
+
+/* static */ void CrashLog::InitialiseCrashLog()
+{
+	for (const int *i = _signals_to_handle; i != endof(_signals_to_handle); i++) {
+		signal(*i, HandleCrash);
+	}
+}
diff --git a/src/os/macosx/macos.h b/src/os/macosx/macos.h
--- a/src/os/macosx/macos.h
+++ b/src/os/macosx/macos.h
@@ -30,29 +30,8 @@
 #endif
 
 
-/*
- * Functions to show the popup window
- * use ShowMacDialog when you want to control title, message and text on the button
- * ShowMacAssertDialog is used by assert
- * ShowMacErrorDialog should be used when an unrecoverable error shows up. It only contains the title, which will should tell what went wrong
- * the function then adds text that tells the user to update and then report the bug if it's present in the newest version
- * It also quits in a nice way since we call it when we know something happened that will crash OpenTTD (like a needed pointer turns out to be NULL or similar)
- */
-void ShowMacDialog ( const char *title, const char *message, const char *buttonLabel );
-void ShowMacAssertDialog ( const char *function, const char *file, const int line, const char *expression );
-void ShowMacErrorDialog(const char *error);
-
-/* Since MacOS X users will never see an assert unless they started the game from a terminal
- * we're using a custom assert(e) macro. */
-#undef assert
-
-#ifdef NDEBUG
-#define assert(e)       ((void)0)
-#else
-
-#define assert(e) \
-		(__builtin_expect(!(e), 0) ? ShowMacAssertDialog ( __func__, __FILE__, __LINE__, #e ): (void)0 )
-#endif
+/** Helper function displaying a message the best possible way. */
+void ShowMacDialog(const char *title, const char *message, const char *button_label);
 
 void GetMacOSVersion(int *return_major, int *return_minor, int *return_bugfix);
 
diff --git a/src/os/macosx/macos.mm b/src/os/macosx/macos.mm
--- a/src/os/macosx/macos.mm
+++ b/src/os/macosx/macos.mm
@@ -10,6 +10,7 @@
 #include "../../stdafx.h"
 #include "../../core/bitmath_func.hpp"
 #include "../../rev.h"
+#include "macos.h"
 
 #define Rect  OTTDRect
 #define Point OTTDPoint
@@ -17,15 +18,6 @@
 #undef Rect
 #undef Point
 
-#include <mach/mach.h>
-#include <mach/mach_host.h>
-#include <mach/host_info.h>
-#include <mach/machine.h>
-
-#ifndef CPU_SUBTYPE_POWERPC_970
-#define CPU_SUBTYPE_POWERPC_970 ((cpu_subtype_t) 100)
-#endif
-
 /*
  * This file contains objective C
  * Apple uses objective C instead of plain C to interact with OS specific/native functions
@@ -62,74 +54,6 @@ void GetMacOSVersion(int *return_major, 
 	}
 }
 
-void ToggleFullScreen(bool fs);
-
-static char *GetOSString()
-{
-	static char buffer[175];
-	const char *CPU;
-	char newgrf[125];
-	// get the hardware info
-	host_basic_info_data_t hostInfo;
-	mach_msg_type_number_t infoCount;
-
-	infoCount = HOST_BASIC_INFO_COUNT;
-	host_info(
-		mach_host_self(), HOST_BASIC_INFO, (host_info_t)&hostInfo, &infoCount
-	);
-
-	// replace the hardware info with strings, that tells a bit more than just an int
-	switch (hostInfo.cpu_subtype) {
-#ifdef __POWERPC__
-		case CPU_SUBTYPE_POWERPC_750:  CPU = "G3"; break;
-		case CPU_SUBTYPE_POWERPC_7400:
-		case CPU_SUBTYPE_POWERPC_7450: CPU = "G4"; break;
-		case CPU_SUBTYPE_POWERPC_970:  CPU = "G5"; break;
-		default:                       CPU = "Unknown PPC"; break;
-#else
-		/* it looks odd to have a switch for two cases, but it leaves room for easy
-		 * expansion. Odds are that Apple will some day use newer CPUs than i686
-		 */
-		case CPU_SUBTYPE_PENTPRO: CPU = "i686"; break;
-		default:                  CPU = "Unknown Intel"; break;
-#endif
-	}
-
-	/* Get the version of OSX */
-	char OS[20];
-	int version_major, version_minor, version_bugfix;
-	GetMacOSVersion(&version_major, &version_minor, &version_bugfix);
-
-	if (version_major != -1 && version_minor != -1 && version_bugfix != -1) {
-		snprintf(OS, lengthof(OS), "%d.%d.%d", version_major, version_minor, version_bugfix);
-	} else {
-		snprintf(OS, lengthof(OS), "uncertain %d.%d.%d", version_major, version_minor, version_bugfix);
-	}
-
-	// make a list of used newgrf files
-/*	if (_first_grffile != NULL) {
-		char *n = newgrf;
-		const GRFFile *file;
-
-		for (file = _first_grffile; file != NULL; file = file->next) {
-			n = strecpy(n, " ", lastof(newgrf));
-			n = strecpy(n, file->filename, lastof(newgrf));
-		}
-	} else {*/
-		sprintf(newgrf, "none");
-//	}
-
-	snprintf(
-		buffer, lengthof(buffer),
-		"Please add this info: (tip: copy-paste works)\n"
-		"CPU: %s, OSX: %s, OpenTTD version: %s\n"
-		"NewGRF files:%s",
-		CPU, OS, _openttd_revision, newgrf
-	);
-	return buffer;
-}
-
-
 #ifdef WITH_SDL
 
 void ShowMacDialog(const char *title, const char *message, const char *buttonLabel)
@@ -139,7 +63,7 @@ void ShowMacDialog(const char *title, co
 
 #elif defined WITH_COCOA
 
-void CocoaDialog(const char *title, const char *message, const char *buttonLabel);
+extern void CocoaDialog(const char *title, const char *message, const char *buttonLabel);
 
 void ShowMacDialog(const char *title, const char *message, const char *buttonLabel)
 {
@@ -156,42 +80,15 @@ void ShowMacDialog(const char *title, co
 
 #endif
 
-void ShowMacAssertDialog(const char *function, const char *file, const int line, const char *expression)
+
+void ShowOSErrorBox(const char *buf, bool system)
 {
-	const char *buffer =
-		[[NSString stringWithFormat:@
-			"An assertion has failed and OpenTTD must quit.\n"
-			"%s in %s (line %d)\n"
-			"\"%s\"\n"
-			"\n"
-			"You should report this error the OpenTTD developers if you think you found a bug.\n"
-			"\n"
-			"%s",
-			function, file, line, expression, GetOSString()] cString
-		];
-	NSLog(@"%s", buffer);
-	ToggleFullScreen(0);
-	ShowMacDialog("Assertion Failed", buffer, "Quit");
-
-	// abort so that a debugger has a chance to notice
-	abort();
-}
-
-
-void ShowMacErrorDialog(const char *error)
-{
-	const char *buffer =
-		[[NSString stringWithFormat:@
-			"Please update to the newest version of OpenTTD\n"
-			"If the problem presists, please report this to\n"
-			"http://bugs.openttd.org\n"
-			"\n"
-			"%s",
-			GetOSString()] cString
-		];
-	ToggleFullScreen(0);
-	ShowMacDialog(error, buffer, "Quit");
-	abort();
+	/* Display the error in the best way possible. */
+	if (system) {
+		ShowMacDialog("OpenTTD has encountered an error", buf, "Quit");
+	} else {
+		ShowMacDialog(buf, "See the readme for more info.\nMost likely you are missing files from the original TTD.", "Quit");
+	}
 }
 
 
diff --git a/src/os/macosx/osx_stdafx.h b/src/os/macosx/osx_stdafx.h
--- a/src/os/macosx/osx_stdafx.h
+++ b/src/os/macosx/osx_stdafx.h
@@ -20,6 +20,12 @@
 #include <sys/cdefs.h>
 #include <unistd.h>
 
+/* Some gcc versions include assert.h via this header. As this would interfere
+ * with our own assert redefinition, include this header first. */
+#if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3))
+#	include <debug/debug.h>
+#endif
+
 /* __LP64__ only exists in 10.5 and higher */
 #if defined(__APPLE__) && !defined(__LP64__)
 #	define __LP64__ 0
diff --git a/src/os/unix/unix.cpp b/src/os/unix/unix.cpp
--- a/src/os/unix/unix.cpp
+++ b/src/os/unix/unix.cpp
@@ -218,21 +218,17 @@ void ShowInfo(const char *str)
 	fprintf(stderr, "%s\n", str);
 }
 
+#if !defined(__APPLE__)
 void ShowOSErrorBox(const char *buf, bool system)
 {
-#if defined(__APPLE__)
-	/* this creates an NSAlertPanel with the contents of 'buf'
-	 * this is the native and nicest way to do this on OSX */
-	ShowMacDialog( buf, "See readme for more info\nMost likely you are missing files from the original TTD", "Quit" );
-#else
 	/* All unix systems, except OSX. Only use escape codes on a TTY. */
 	if (isatty(fileno(stderr))) {
 		fprintf(stderr, "\033[1;31mError: %s\033[0;39m\n", buf);
 	} else {
 		fprintf(stderr, "Error: %s\n", buf);
 	}
+}
 #endif
-}
 
 #ifdef WITH_COCOA
 void cocoaSetupAutoreleasePool();
diff --git a/src/stdafx.h b/src/stdafx.h
--- a/src/stdafx.h
+++ b/src/stdafx.h
@@ -58,14 +58,7 @@
 #include <cstring>
 #include <cstdlib>
 #include <climits>
-
-/* MacOS X will use an NSAlert to display failed assertaions since they're lost unless running from a terminal
- * strgen always runs from terminal and don't need a window for asserts */
-#if !defined(__APPLE__) || defined(STRGEN)
-	#include <cassert>
-#else
-	#include "os/macosx/macos.h"
-#endif
+#include <cassert>
 
 #if defined(UNIX) || defined(__MINGW32__)
 	#include <sys/types.h>
diff --git a/src/video/cocoa/cocoa_v.mm b/src/video/cocoa/cocoa_v.mm
--- a/src/video/cocoa/cocoa_v.mm
+++ b/src/video/cocoa/cocoa_v.mm
@@ -16,6 +16,7 @@
 #ifdef WITH_COCOA
 
 #include "../../stdafx.h"
+#include "../../os/macosx/macos.h"
 
 #define Rect  OTTDRect
 #define Point OTTDPoint
diff --git a/src/video/cocoa/wnd_quartz.mm b/src/video/cocoa/wnd_quartz.mm
--- a/src/video/cocoa/wnd_quartz.mm
+++ b/src/video/cocoa/wnd_quartz.mm
@@ -17,6 +17,7 @@
 #ifdef ENABLE_COCOA_QUARTZ
 
 #include "../../stdafx.h"
+#include "../../os/macosx/macos.h"
 
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
 
diff --git a/src/video/cocoa/wnd_quickdraw.mm b/src/video/cocoa/wnd_quickdraw.mm
--- a/src/video/cocoa/wnd_quickdraw.mm
+++ b/src/video/cocoa/wnd_quickdraw.mm
@@ -18,6 +18,7 @@
 
 #define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_3
 #include "../../stdafx.h"
+#include "../../os/macosx/macos.h"
 
 #define Rect  OTTDRect
 #define Point OTTDPoint