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launch-cache/update_dyld_shared_cache.cpp /dev/null dyld-132.13
--- /dev/null
+++ dyld/dyld-132.13/launch-cache/update_dyld_shared_cache.cpp
@@ -0,0 +1,2583 @@
+/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*- 
+ *
+ * Copyright (c) 2006-2009 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <mach/mach.h>
+#include <mach/mach_time.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <errno.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#include <sys/resource.h>
+#include <dirent.h>
+#include <servers/bootstrap.h>
+#include <mach-o/loader.h>
+#include <mach-o/fat.h>
+#include <vproc.h>
+#include <vproc_priv.h>
+
+#include "dyld_cache_format.h"
+
+#include <vector>
+#include <set>
+#include <map>
+#include <ext/hash_map>
+
+#include "Architectures.hpp"
+#include "MachOLayout.hpp"
+#include "MachORebaser.hpp"
+#include "MachOBinder.hpp"
+#include "CacheFileAbstraction.hpp"
+
+#define SELOPT_WRITE
+#include <objc/objc-selopt.h>
+
+
+static bool							verbose = false;
+static bool							progress = false;
+static std::vector<const char*>		warnings;
+
+
+static void warn(const char *arch, const char *format, ...)
+{
+    char *msg;
+
+    va_list args;
+    va_start(args, format);
+    ::vasprintf(&msg, format, args);
+    va_end(args);
+    
+    warnings.push_back(msg);
+    
+    if ( verbose ) {
+        ::fprintf(::stderr, "update_dyld_shared_cache: warning: %s%s%s%s\n", 
+                  arch ? "for arch " : "", 
+                  arch ? arch : "", 
+                  arch ? ", " : "", 
+                  msg);
+    }
+}
+
+
+static uint64_t pageAlign(uint64_t addr) { return ( (addr + 4095) & (-4096) ); }
+
+class ArchGraph
+{
+public:
+	static void			addArchPair(ArchPair ap);
+	static void			addRoot(const char* vpath, const std::set<ArchPair>& archs);
+	static void			findSharedDylibs(ArchPair ap);
+	static ArchGraph*	graphForArchPair(ArchPair ap) { return fgPerArchGraph[ap]; }
+	static void			setFileSystemRoot(const char* root, bool usesOverlay) { fgFileSystemRoot = root; fgUsesOverlay = usesOverlay; }
+	static const char*	archName(ArchPair ap);
+	
+	ArchPair											getArchPair() { return fArchPair; }
+	std::set<const class MachOLayoutAbstraction*>&		getSharedDylibs() { return fSharedDylibs; }
+	const char*											archName() { return archName(fArchPair); }
+	
+private:
+	
+	class DependencyNode
+	{
+	public:
+										DependencyNode(ArchGraph*, const char* path, const MachOLayoutAbstraction* layout);
+		void							loadDependencies(const MachOLayoutAbstraction*);
+		void							markNeededByRoot(DependencyNode*);
+		const char*						getPath() const { return fPath; }
+		const MachOLayoutAbstraction*	getLayout() const { return fLayout; }
+		size_t							useCount() const { return fRootsDependentOnThis.size(); }
+		bool							allDependentsFound() const { return !fDependentMissing; }
+	private:
+		ArchGraph*									fGraph;
+		const char*									fPath;
+		const MachOLayoutAbstraction*				fLayout;
+		bool										fDependenciesLoaded;
+		bool										fDependentMissing;
+		std::set<DependencyNode*>					fDependsOn;
+		std::set<DependencyNode*>					fRootsDependentOnThis;
+	};
+
+	struct CStringEquals {
+		bool operator()(const char* left, const char* right) const { return (strcmp(left, right) == 0); }
+	};
+	typedef __gnu_cxx::hash_map<const char*, class DependencyNode*, __gnu_cxx::hash<const char*>, CStringEquals> PathToNode;
+
+
+								ArchGraph(ArchPair ap) : fArchPair(ap) {}
+	void						addRoot(const char* path, const MachOLayoutAbstraction*);
+	DependencyNode*				getNode(const char* path);
+	DependencyNode*				getNodeForVirtualPath(const char* vpath);
+	static bool					canBeShared(const MachOLayoutAbstraction* layout, ArchPair ap, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap);
+
+	static std::map<ArchPair, ArchGraph*>	fgPerArchGraph;
+	static const char*						fgFileSystemRoot;
+	static bool								fgUsesOverlay;
+	
+	ArchPair									fArchPair;
+	std::set<DependencyNode*>					fRoots;
+	PathToNode									fNodes;
+	std::set<const MachOLayoutAbstraction*>		fSharedDylibs;  // use set to avoid duplicates when installname!=realpath
+};
+std::map<ArchPair, ArchGraph*>		ArchGraph::fgPerArchGraph;
+const char*							ArchGraph::fgFileSystemRoot = "";
+bool								ArchGraph::fgUsesOverlay = false;
+
+void ArchGraph::addArchPair(ArchPair ap)
+{
+	//fprintf(stderr, "adding ArchPair 0x%08X,0x%08X\n", ap.arch, ap.subtype);
+	fgPerArchGraph[ap] = new ArchGraph(ap);
+}
+
+void ArchGraph::addRoot(const char* vpath, const std::set<ArchPair>& onlyArchs)
+{
+	char completePath[strlen(fgFileSystemRoot)+strlen(vpath)+2];
+	const char* path = NULL;
+	if ( strlen(fgFileSystemRoot) == 0 ) {
+		path = vpath;
+	}
+	else {
+		strcpy(completePath, fgFileSystemRoot);
+		strcat(completePath, vpath);	// assumes vpath starts with '/'
+		if ( fgUsesOverlay ) {
+			// using -overlay means if /overlay/usr/lib exists use it, otherwise use original path
+			struct stat stat_buf;
+			if ( stat(completePath, &stat_buf) == 0 )
+				path = completePath;
+			else
+				path = vpath;
+		}
+		else {
+			// using -root means alway redirect /usr/lib to /rootpath/usr/lib
+			path = completePath;
+		}
+	}
+	try {
+		const UniversalMachOLayout& uni = UniversalMachOLayout::find(path, &onlyArchs);
+		for(std::set<ArchPair>::iterator ait = onlyArchs.begin(); ait != onlyArchs.end(); ++ait) {
+			try {
+				const MachOLayoutAbstraction* layout = uni.getSlice(*ait);
+				fgPerArchGraph[*ait]->addRoot(path, layout);
+			}
+			catch (const char* msg) {
+				if ( verbose ) 
+					fprintf(stderr, "update_dyld_shared_cache: warning for %s can't use root %s: %s\n", fgPerArchGraph[*ait]->archName(), path, msg);
+			}
+			
+		}
+	}
+	catch (const char* msg) {
+		fprintf(stderr, "update_dyld_shared_cache: warning can't use root %s: %s\n", path, msg);
+	}
+}
+
+
+
+void ArchGraph::addRoot(const char* path, const MachOLayoutAbstraction* layout)
+{
+	if ( verbose )
+		fprintf(stderr, "update_dyld_shared_cache: adding root: %s\n", path);
+	DependencyNode*	node = this->getNode(path);
+	fRoots.insert(node);
+	const MachOLayoutAbstraction* mainExecutableLayout = NULL;
+	if ( layout->getFileType() == MH_EXECUTE )
+		mainExecutableLayout = layout;
+	node->loadDependencies(mainExecutableLayout);
+	node->markNeededByRoot(node);
+	if ( layout->getFileType() == MH_DYLIB )
+		node->markNeededByRoot(NULL);
+}
+
+// a virtual path does not have the fgFileSystemRoot prefix
+ArchGraph::DependencyNode* ArchGraph::getNodeForVirtualPath(const char* vpath)
+{
+	if ( fgFileSystemRoot == NULL ) {
+		return this->getNode(vpath);
+	}
+	else {
+		char completePath[strlen(fgFileSystemRoot)+strlen(vpath)+2];
+		strcpy(completePath, fgFileSystemRoot);
+		strcat(completePath, vpath);	// assumes vpath starts with '/'
+		if ( fgUsesOverlay ) {
+			// using -overlay means if /overlay/usr/lib exists use it, otherwise use original path
+			struct stat stat_buf;
+			if ( stat(completePath, &stat_buf) == 0 )
+				return this->getNode(completePath);
+			else
+				return this->getNode(vpath);
+		}
+		else {
+			// using -root means always use /rootpath/usr/lib
+			return this->getNode(completePath);
+		}
+	}
+}
+
+ArchGraph::DependencyNode* ArchGraph::getNode(const char* path)
+{
+	// look up supplied path to see if node already exists
+	PathToNode::iterator pos = fNodes.find(path);
+	if ( pos != fNodes.end() )
+		return pos->second;
+	
+	// get real path
+	char realPath[MAXPATHLEN];
+	if ( realpath(path, realPath) == NULL )
+		throwf("realpath() failed on %s\n", path);
+	
+	// look up real path to see if node already exists
+	pos = fNodes.find(realPath);
+	if ( pos != fNodes.end() )
+		return pos->second;
+	
+	// still does not exist, so create a new node
+	const UniversalMachOLayout& uni = UniversalMachOLayout::find(realPath);
+	DependencyNode* node = new DependencyNode(this, realPath, uni.getSlice(fArchPair));
+	if ( node->getLayout() == NULL ) {
+		throwf("%s is missing arch %s", realPath, archName(fArchPair));
+	}
+	// add realpath to node map
+	fNodes[node->getPath()] = node;
+	// if install name is not real path, add install name to node map
+	if ( (node->getLayout()->getFileType() == MH_DYLIB) && (strcmp(realPath, node->getLayout()->getID().name) != 0) ) {
+		//fprintf(stderr, "adding node alias 0x%08X %s for %s\n", fArch, node->getLayout()->getID().name, realPath);
+		fNodes[node->getLayout()->getID().name] = node;
+	}
+	return node;
+}
+	
+	
+void ArchGraph::DependencyNode::loadDependencies(const MachOLayoutAbstraction* mainExecutableLayout)
+{
+	if ( !fDependenciesLoaded ) {
+		fDependenciesLoaded = true;
+		// add dependencies
+		const std::vector<MachOLayoutAbstraction::Library>&	dependsOn = fLayout->getLibraries();
+		for(std::vector<MachOLayoutAbstraction::Library>::const_iterator it = dependsOn.begin(); it != dependsOn.end(); ++it) {
+			try {
+				const char* dependentPath = it->name;
+				if ( strncmp(dependentPath, "@executable_path/", 17) == 0 ) {
+					if ( mainExecutableLayout == NULL )
+						throw "@executable_path without main executable";
+					// expand @executable_path path prefix
+					const char* executablePath = mainExecutableLayout->getFilePath();
+					char newPath[strlen(executablePath) + strlen(dependentPath)+2];
+					strcpy(newPath, executablePath);
+					char* addPoint = strrchr(newPath,'/');
+					if ( addPoint != NULL )
+						strcpy(&addPoint[1], &dependentPath[17]);
+					else
+						strcpy(newPath, &dependentPath[17]);
+					dependentPath = strdup(newPath);
+				}
+				else if ( strncmp(dependentPath, "@loader_path/", 13) == 0 ) {
+					// expand @loader_path path prefix
+					char newPath[strlen(fPath) + strlen(dependentPath)+2];
+					strcpy(newPath, fPath);
+					char* addPoint = strrchr(newPath,'/');
+					if ( addPoint != NULL )
+						strcpy(&addPoint[1], &dependentPath[13]);
+					else
+						strcpy(newPath, &dependentPath[13]);
+					dependentPath = strdup(newPath);
+				}
+				else if ( strncmp(dependentPath, "@rpath/", 7) == 0 ) {
+					throw "@rpath not supported in dyld shared cache";
+				}
+				fDependsOn.insert(fGraph->getNodeForVirtualPath(dependentPath));
+			}
+			catch (const char* msg) {
+				if ( it->weakImport && ! fLayout->hasSplitSegInfo() ) {
+					// ok to ignore missing weak imported dylibs from things that are
+					// not going to be in the dyld shared cache
+				}
+				else {
+					fprintf(stderr, "warning, could not bind %s because %s\n", fPath, msg);
+					fDependentMissing = true;
+				}
+			}
+		}
+		// recurse
+		for(std::set<DependencyNode*>::iterator it = fDependsOn.begin(); it != fDependsOn.end(); ++it) {
+			(*it)->loadDependencies(mainExecutableLayout);
+		}
+	}
+}
+
+void ArchGraph::DependencyNode::markNeededByRoot(ArchGraph::DependencyNode* rootNode)
+{
+	if ( fRootsDependentOnThis.count(rootNode) == 0 ) {
+		fRootsDependentOnThis.insert(rootNode);
+		for(std::set<DependencyNode*>::iterator it = fDependsOn.begin(); it != fDependsOn.end(); ++it) {
+			(*it)->markNeededByRoot(rootNode);
+		}
+	}
+}
+
+
+ArchGraph::DependencyNode::DependencyNode(ArchGraph* graph, const char* path, const MachOLayoutAbstraction* layout) 
+ : fGraph(graph), fPath(strdup(path)), fLayout(layout), fDependenciesLoaded(false), fDependentMissing(false)
+{
+	//fprintf(stderr, "new DependencyNode(0x%08X, %s)\n", graph->fArch, path);
+}
+
+void ArchGraph::findSharedDylibs(ArchPair ap)
+{
+	const PathToNode& nodes = fgPerArchGraph[ap]->fNodes;
+	std::set<const MachOLayoutAbstraction*> possibleLibs;
+	//fprintf(stderr, "shared for arch 0x%08X\n", arch);
+	for(PathToNode::const_iterator it = nodes.begin(); it != nodes.end(); ++it) {
+		DependencyNode* node = it->second;
+		// <rdar://problem/6127437> put all dylibs in shared cache - not just ones used by more than one app
+		if ( node->allDependentsFound() /*&& (node->useCount() > 1)*/ ) {
+			const MachOLayoutAbstraction* layout = node->getLayout();
+			if ( layout->hasSplitSegInfo() && layout->isRootOwned() && layout->inSharableLocation() ) 
+				possibleLibs.insert(layout);
+			//fprintf(stderr, "\t%s\n", it->first);
+		}
+	}
+	
+	// prune so that all shareable libs depend only on other shareable libs
+	std::set<const MachOLayoutAbstraction*>& sharedLibs = fgPerArchGraph[ap]->fSharedDylibs;
+	std::map<const MachOLayoutAbstraction*,bool> shareableMap;
+	for (std::set<const MachOLayoutAbstraction*>::iterator lit = possibleLibs.begin(); lit != possibleLibs.end(); ++lit) {
+		if ( canBeShared(*lit, ap, possibleLibs, shareableMap) )
+			sharedLibs.insert(*lit);
+	}
+}
+
+const char*	ArchGraph::archName(ArchPair ap)
+{
+	switch ( ap.arch ) {
+		case CPU_TYPE_POWERPC:
+			return "ppc";
+		case CPU_TYPE_I386:
+			return "i386";
+		case CPU_TYPE_X86_64:
+			return "x86_64";
+		case CPU_TYPE_ARM:
+			switch ( ap.subtype ) {
+				case CPU_SUBTYPE_ARM_V4T:
+					return "armv4t";
+				case CPU_SUBTYPE_ARM_V6:
+					return "armv6";
+				case CPU_SUBTYPE_ARM_V5TEJ:
+					return "armv5";
+				case CPU_SUBTYPE_ARM_XSCALE:
+					return "arm-xscale";
+				case CPU_SUBTYPE_ARM_V7:
+					return "armv7";
+				default:
+					return "arm";
+			}
+		default:
+			return "unknown";
+	}
+}
+
+bool ArchGraph::canBeShared(const MachOLayoutAbstraction* layout, ArchPair ap, const std::set<const MachOLayoutAbstraction*>& possibleLibs, std::map<const MachOLayoutAbstraction*, bool>& shareableMap)
+{
+	// check map which is a cache of results
+	std::map<const MachOLayoutAbstraction*, bool>::iterator mapPos = shareableMap.find(layout);
+	if ( mapPos != shareableMap.end() ) {
+		return mapPos->second;
+	}
+	// see if possible
+	if ( possibleLibs.count(layout) == 0 ) {
+		shareableMap[layout] = false;
+		char* msg;
+		if ( ! layout->hasSplitSegInfo() )
+			asprintf(&msg, "can't put %s in shared cache because it was not built for 10.5 or later", layout->getID().name);
+		else if ( ! layout->isRootOwned() )
+			asprintf(&msg, "can't put %s in shared cache because it is not owned by root", layout->getID().name);
+		else if ( ! layout->inSharableLocation() )
+			asprintf(&msg, "can't put %s in shared cache because it is not in /usr/lib or /System/Library", layout->getID().name);
+		else
+			asprintf(&msg, "can't put %s in shared cache", layout->getID().name);
+		warnings.push_back(msg);
+		if ( verbose )
+			fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
+		return false;
+	}
+	// look recursively
+	shareableMap[layout] = true; // mark this shareable early in case of circular references
+	const PathToNode& nodes = fgPerArchGraph[ap]->fNodes;
+	const std::vector<MachOLayoutAbstraction::Library>&	dependents = layout->getLibraries();
+	for (std::vector<MachOLayoutAbstraction::Library>::const_iterator dit = dependents.begin(); dit != dependents.end(); ++dit) {
+		PathToNode::const_iterator pos = nodes.find(dit->name);
+		if ( pos == nodes.end() ) {
+			// path from load command does not match any loaded dylibs, maybe there is a temp symlink
+			char realPath[MAXPATHLEN];
+			if ( realpath(dit->name, realPath) != NULL ) {
+				if ( nodes.find(realPath) != nodes.end() )
+					continue;
+			}
+			shareableMap[layout] = false;
+			char* msg;
+			asprintf(&msg, "can't put %s in shared cache because it depends on %s which can't be found", layout->getID().name, dit->name);
+			warnings.push_back(msg);
+			if ( verbose )
+				fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
+			return false;
+		}
+		else {
+			if ( ! canBeShared(pos->second->getLayout(), ap, possibleLibs, shareableMap) ) {
+				shareableMap[layout] = false;
+				char* msg;
+				asprintf(&msg, "can't put %s in shared cache because it depends on %s which can't be in shared cache", layout->getID().name, dit->name);
+				warnings.push_back(msg);
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: for arch %s, %s\n", archName(ap), msg);
+				return false;
+			}
+		}
+	}
+	return true;
+}
+
+
+template <typename A>
+class SharedCache
+{
+public:
+							SharedCache(ArchGraph* graph, const char* rootPath, bool alphaSort, bool verify, bool optimize, bool overlay, uint64_t dyldBaseAddress);
+	bool					update(bool usesOverlay, bool force, bool optimize, bool deleteExistingFirst, int archIndex, 
+										int archCount, bool keepSignatures);
+	static const char*		cacheFileSuffix(bool optimized, const char* archName);
+
+    uint64_t				mappedCacheAddressForAddress(uint64_t addr);
+
+private:
+	typedef typename A::P			P;
+    typedef typename A::P::E		E;
+    typedef typename A::P::uint_t	pint_t;
+
+	bool					notUpToDate(const char* path);
+	bool					notUpToDate(const void* cache);
+	uint8_t*				optimizeLINKEDIT(bool keepSignatures);
+	void					optimizeObjC();
+
+	static void				getSharedCacheBasAddresses(cpu_type_t arch, uint64_t* baseReadOnly, uint64_t* baseWritable);
+	static cpu_type_t		arch();
+	static const char*		archName();
+	static uint64_t			sharedRegionReadOnlyStartAddress();
+	static uint64_t			sharedRegionWritableStartAddress();
+	static uint64_t			sharedRegionReadOnlySize();
+	static uint64_t			sharedRegionWritableSize();
+	static uint64_t			getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide);
+	
+	
+	void					assignNewBaseAddresses();
+	uint64_t				cacheFileOffsetForAddress(uint64_t addr);
+
+	struct LayoutInfo {
+		const MachOLayoutAbstraction*		layout;
+		dyld_cache_image_info				info;
+	};
+	
+	struct ByNameSorter {
+		bool operator()(const LayoutInfo& left, const LayoutInfo& right) 
+				{ return (strcmp(left.layout->getID().name, right.layout->getID().name) < 0); }
+	};
+
+    struct ByCStringSectionSizeSorter {
+        bool operator()(const LayoutInfo& left, const LayoutInfo& right) {
+            const std::vector<MachOLayoutAbstraction::Segment>& segs_l =
+                left.layout->getSegments();
+            const std::vector<MachOLayoutAbstraction::Segment>& segs_r = 
+                right.layout->getSegments();
+            if (segs_l.size() == 0  ||  segs_r.size() == 0) {
+                // one image has no segments
+                return segs_l.size() > segs_r.size();
+            }
+            const macho_header<P> *mh_l = (const macho_header<P>*)segs_l[0].mappedAddress();
+            const macho_header<P> *mh_r = (const macho_header<P>*)segs_r[0].mappedAddress();
+            const macho_section<P> *cstring_l = mh_l->getSection("__TEXT", "__cstring");
+            const macho_section<P> *cstring_r = mh_r->getSection("__TEXT", "__cstring");
+            if (!cstring_l  ||  !cstring_r) {
+                // one image has no cstrings
+                return cstring_l && !cstring_r;
+            }
+
+            return cstring_l->size() > cstring_r->size();
+        }
+    };
+
+	struct Sorter {
+		Sorter(std::map<const MachOLayoutAbstraction*, uint32_t>& map): fMap(map) {}
+		bool operator()(const LayoutInfo& left, const LayoutInfo& right) {
+			return (fMap[left.layout] < fMap[right.layout]); 
+		}
+	private:
+		std::map<const MachOLayoutAbstraction*, uint32_t>& fMap;
+	};
+	
+
+	ArchGraph*							fArchGraph;
+	const bool							fVerify;
+	bool								fExistingIsNotUpToDate;
+	const char*							fCacheFilePath;
+	uint8_t*							fExistingCacheForVerification;
+	std::vector<LayoutInfo>				fDylibs;
+	std::vector<shared_file_mapping_np>	fMappings;
+	uint32_t							fHeaderSize;
+    uint8_t*							fInMemoryCache;
+	uint64_t							fDyldBaseAddress;
+	uint64_t							fLinkEditsTotalUnoptimizedSize;
+	uint64_t							fLinkEditsStartAddress;
+	MachOLayoutAbstraction::Segment*	fFirstLinkEditSegment;
+	uint32_t							fOffsetOfBindInfoInCombinedLinkedit;
+	uint32_t							fOffsetOfWeakBindInfoInCombinedLinkedit;
+	uint32_t							fOffsetOfLazyBindInfoInCombinedLinkedit;
+	uint32_t							fOffsetOfExportInfoInCombinedLinkedit;
+	uint32_t							fOffsetOfOldSymbolTableInfoInCombinedLinkedit;
+	uint32_t							fLinkEditsTotalOptimizedSize;
+};
+
+
+// Access a section containing a list of pointers
+template <typename A, typename T>
+class PointerSection 
+{
+    typedef typename A::P P;
+    typedef typename A::P::uint_t pint_t;
+
+    SharedCache<A>* const fCache;
+    const macho_section<P>* const fSection;
+    pint_t * const fBase;
+    uint64_t const fCount;
+
+public:
+    PointerSection(SharedCache<A>* cache, const macho_header<P>* header, 
+                   const char *segname, const char *sectname)
+        : fCache(cache)
+        , fSection(header->getSection(segname, sectname))
+        , fBase(fSection ? (pint_t *)cache->mappedCacheAddressForAddress(fSection->addr()) : 0)
+        , fCount(fSection ? fSection->size() / sizeof(pint_t) : 0)
+    {
+    }
+
+    uint64_t count() const { return fCount; }
+
+    uint64_t getUnmapped(uint64_t index) const {
+        if (index >= fCount) throwf("index out of range");
+        return P::getP(fBase[index]);
+    }
+
+    T get(uint64_t index) const { 
+        return (T)fCache->mappedCacheAddressForAddress(getUnmapped(index));
+    }
+
+    void set(uint64_t index, uint64_t value) {
+        if (index >= fCount) throwf("index out of range");
+        P::setP(fBase[index], value);
+    }
+};
+
+// Access a section containing an array of structures
+template <typename A, typename T>
+class ArraySection 
+{
+    typedef typename A::P P;
+
+    SharedCache<A>* const fCache;
+    const macho_section<P>* const fSection;
+    T * const fBase;
+    uint64_t const fCount;
+
+public:
+    ArraySection(SharedCache<A>* cache, const macho_header<P>* header, 
+                 const char *segname, const char *sectname)
+        : fCache(cache)
+        , fSection(header->getSection(segname, sectname))
+        , fBase(fSection ? (T *)cache->mappedCacheAddressForAddress(fSection->addr()) : 0)
+        , fCount(fSection ? fSection->size() / sizeof(T) : 0)
+    {
+    }
+
+    uint64_t count() const { return fCount; }
+
+    T& get(uint64_t index) const { 
+        if (index >= fCount) throwf("index out of range");
+        return fBase[index];
+    }
+};
+
+
+// GrP fixme
+#include "ObjCLegacyAbstraction.hpp"
+#include "ObjCModernAbstraction.hpp"
+
+
+	
+template <>	 cpu_type_t	SharedCache<ppc>::arch()	{ return CPU_TYPE_POWERPC; }
+template <>	 cpu_type_t	SharedCache<x86>::arch()	{ return CPU_TYPE_I386; }
+template <>	 cpu_type_t	SharedCache<x86_64>::arch()	{ return CPU_TYPE_X86_64; }
+template <>	 cpu_type_t	SharedCache<arm>::arch()	{ return CPU_TYPE_ARM; }
+
+template <>	 uint64_t	SharedCache<ppc>::sharedRegionReadOnlyStartAddress()	{ return 0x90000000; }
+template <>	 uint64_t	SharedCache<x86>::sharedRegionReadOnlyStartAddress()	{ return 0x90000000; }
+template <>	 uint64_t	SharedCache<x86_64>::sharedRegionReadOnlyStartAddress()	{ return 0x7FFF80000000LL; }
+template <>	 uint64_t	SharedCache<arm>::sharedRegionReadOnlyStartAddress()	{ return 0x30000000; }
+
+template <>	 uint64_t	SharedCache<ppc>::sharedRegionWritableStartAddress()	{ return 0xA0000000; }
+template <>	 uint64_t	SharedCache<x86>::sharedRegionWritableStartAddress()	{ return 0xA0000000; }
+template <>	 uint64_t	SharedCache<x86_64>::sharedRegionWritableStartAddress()	{ return 0x7FFF70000000LL; }
+template <>	 uint64_t	SharedCache<arm>::sharedRegionWritableStartAddress()	{ return 0x38000000; }
+
+template <>	 uint64_t	SharedCache<ppc>::sharedRegionReadOnlySize()			{ return 0x10000000; }
+template <>	 uint64_t	SharedCache<x86>::sharedRegionReadOnlySize()			{ return 0x10000000; }
+template <>	 uint64_t	SharedCache<x86_64>::sharedRegionReadOnlySize()			{ return 0x7FE00000; }
+template <>	 uint64_t	SharedCache<arm>::sharedRegionReadOnlySize()			{ return 0x08000000; }
+
+template <>	 uint64_t	SharedCache<ppc>::sharedRegionWritableSize()			{ return 0x10000000; }
+template <>	 uint64_t	SharedCache<x86>::sharedRegionWritableSize()			{ return 0x10000000; }
+template <>	 uint64_t	SharedCache<x86_64>::sharedRegionWritableSize()			{ return 0x20000000; }
+template <>	 uint64_t	SharedCache<arm>::sharedRegionWritableSize()			{ return 0x08000000; }
+
+
+template <>	 const char*	SharedCache<ppc>::archName()	{ return "ppc"; }
+template <>	 const char*	SharedCache<x86>::archName()	{ return "i386"; }
+template <>	 const char*	SharedCache<x86_64>::archName()	{ return "x86_64"; }
+template <>	 const char*	SharedCache<arm>::archName()	{ return "arm"; }
+
+template <>	 const char*	SharedCache<ppc>::cacheFileSuffix(bool optimized, const char*)	{ return optimized ? "ppc" : "rosetta"; }
+template <>	 const char*	SharedCache<x86>::cacheFileSuffix(bool, const char* archName)	{ return archName; }
+template <>	 const char*	SharedCache<x86_64>::cacheFileSuffix(bool, const char* archName){ return archName; }
+template <>	 const char*	SharedCache<arm>::cacheFileSuffix(bool, const char* archName)	{ return archName; }
+
+template <typename A>
+SharedCache<A>::SharedCache(ArchGraph* graph, const char* rootPath, bool alphaSort, bool verify, bool optimize, bool overlay, uint64_t dyldBaseAddress) 
+  : fArchGraph(graph), fVerify(verify), fExistingIsNotUpToDate(true), fCacheFilePath(NULL),
+	fExistingCacheForVerification(NULL), fDyldBaseAddress(dyldBaseAddress)
+{
+	if ( fArchGraph->getArchPair().arch != arch() )
+		throwf("SharedCache object is wrong architecture: 0x%08X vs 0x%08X", fArchGraph->getArchPair().arch, arch());
+		
+	// build vector of all shared dylibs
+	std::set<const MachOLayoutAbstraction*>& dylibs = fArchGraph->getSharedDylibs();
+	for(std::set<const MachOLayoutAbstraction*>::iterator it = dylibs.begin(); it != dylibs.end(); ++it) {
+		const MachOLayoutAbstraction* lib = *it;
+		LayoutInfo temp;
+		temp.layout = lib;
+		temp.info.address = 0;
+		temp.info.modTime = lib->getLastModTime();
+		temp.info.inode = lib->getInode();
+		temp.info.pathFileOffset = lib->getNameFileOffset();
+		fDylibs.push_back(temp);
+	}
+
+	// examine the existing shared cache file
+	char cachePath[1024];
+	strcpy(cachePath, rootPath);
+	strcat(cachePath, DYLD_SHARED_CACHE_DIR);
+	strcat(cachePath, DYLD_SHARED_CACHE_BASE_NAME);
+	strcat(cachePath, cacheFileSuffix(optimize, fArchGraph->archName()));
+	fCacheFilePath = strdup(cachePath);
+	const char* pathToExistingCacheFile = fCacheFilePath;
+	char cachePathNonOverlay[1024];
+	if ( overlay ) {
+		strcpy(cachePathNonOverlay, DYLD_SHARED_CACHE_DIR);
+		strcat(cachePathNonOverlay, DYLD_SHARED_CACHE_BASE_NAME);
+		strcat(cachePathNonOverlay, cacheFileSuffix(optimize, fArchGraph->archName()));
+		pathToExistingCacheFile = cachePathNonOverlay;
+	}
+	fExistingIsNotUpToDate = this->notUpToDate(pathToExistingCacheFile);
+	
+	// sort shared dylibs
+	if ( verify ) {
+		// already sorted by notUpToDate()
+	}
+	else if ( alphaSort ) {
+		std::sort(fDylibs.begin(), fDylibs.end(), ByNameSorter());
+	}
+	else {
+		// random sort for Address Space Randomization
+		std::map<const MachOLayoutAbstraction*, uint32_t> map;
+		for(typename std::vector<struct LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) 
+			map[it->layout] = arc4random();
+		std::sort(fDylibs.begin(), fDylibs.end(), Sorter(map));
+	}
+	
+	// assign segments in each dylib a new address
+	this->assignNewBaseAddresses();
+	
+	// check that cache we are about to create for verification purposes has same layout as existing cache
+	if ( verify ) {
+		// if no existing cache, say so
+		if ( fExistingCacheForVerification == NULL ) {
+			throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify because cache file does not exist in /var/db/dyld/\n",
+			 getpid(), archName());
+		}
+		const dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)fExistingCacheForVerification;
+		const dyldCacheImageInfo<E>* cacheEntry = (dyldCacheImageInfo<E>*)(fExistingCacheForVerification + header->imagesOffset());
+		for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++cacheEntry) {
+			if ( cacheEntry->address() != it->layout->getSegments()[0].newAddress() ) {
+				throwf("update_dyld_shared_cache[%u] warning: for arch=%s, could not verify cache because start address of %s is 0x%llX in cache, but should be 0x%llX\n",
+							getpid(), archName(), it->layout->getID().name, cacheEntry->address(), it->layout->getSegments()[0].newAddress());
+			}
+		}
+	}
+	
+	// calculate cache file header size
+	fHeaderSize = pageAlign(sizeof(dyld_cache_header) 
+							+ fMappings.size()*sizeof(shared_file_mapping_np) 
+							+ fDylibs.size()*sizeof(dyld_cache_image_info) );
+							//+ fDependencyPool.size()*sizeof(uint16_t));
+	
+	if ( fHeaderSize > 0x3000 )
+		throwf("header size miscalculation 0x%08X", fHeaderSize);
+}
+
+
+template <typename A>
+uint64_t SharedCache<A>::getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide)
+{
+	return proposedNewAddress;
+}
+
+template <>
+uint64_t SharedCache<ppc>::getWritableSegmentNewAddress(uint64_t proposedNewAddress, uint64_t originalAddress, uint64_t executableSlide)
+{
+	// for ppc writable segments can only move in increments of 64K (so only hi16 instruction needs to be modified)
+	return (((executableSlide & 0x000000000000F000ULL) - ((proposedNewAddress - originalAddress) & 0x000000000000F000ULL)) & 0x000000000000F000ULL) + proposedNewAddress;
+}
+
+
+template <typename A>
+void SharedCache<A>::assignNewBaseAddresses()
+{
+	// first layout TEXT and DATA for split-seg (or can be split-seg) dylibs
+	uint64_t currentExecuteAddress = sharedRegionReadOnlyStartAddress() + 0x3000;	
+	uint64_t currentWritableAddress = sharedRegionWritableStartAddress();
+	for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+		MachOLayoutAbstraction::Segment* executableSegment = NULL;
+		for (int i=0; i < segs.size(); ++i) {
+			MachOLayoutAbstraction::Segment& seg = segs[i];
+			seg.reset();
+			if ( seg.writable() ) {
+				if ( seg.executable() && it->layout->hasSplitSegInfo() ) {
+					// skip __IMPORT segments in this pass
+				}
+				else {
+					// __DATA segment
+					// for ppc, writable segments have to move in 64K increments
+					if (  it->layout->hasSplitSegInfo() ) {
+						if ( executableSegment == NULL )
+							throwf("first segment in dylib is not executable for %s", it->layout->getID().name);
+						seg.setNewAddress(getWritableSegmentNewAddress(currentWritableAddress, seg.address(), executableSegment->newAddress() - executableSegment->address()));
+					}
+					else
+						seg.setNewAddress(currentWritableAddress);
+					currentWritableAddress = pageAlign(seg.newAddress() + seg.size());
+				}
+			}
+			else {
+				if ( seg.executable() ) {
+					// __TEXT segment
+					if ( it->info.address == 0 )
+						it->info.address = currentExecuteAddress;
+					executableSegment = &seg;
+					seg.setNewAddress(currentExecuteAddress);
+					currentExecuteAddress += pageAlign(seg.size());
+				}
+				else {
+					// skip read-only segments in this pass
+				}
+			}
+		}
+	}
+
+	// append all read-only (but not LINKEDIT) segments at end of all TEXT segments
+	// append all IMPORT segments at end of all DATA segments rounded to next 2MB 
+	uint64_t currentReadOnlyAddress = currentExecuteAddress;
+	uint64_t startWritableExecutableAddress = (currentWritableAddress + 0x200000 - 1) & (-0x200000);
+	uint64_t currentWritableExecutableAddress = startWritableExecutableAddress;
+	for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+		for(int i=0; i < segs.size(); ++i) {
+			MachOLayoutAbstraction::Segment& seg = segs[i];
+			if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") != 0) ) {
+				// allocate non-executable,read-only segments from end of read only shared region
+				seg.setNewAddress(currentReadOnlyAddress);
+				currentReadOnlyAddress += pageAlign(seg.size());
+			}
+			else if ( seg.writable() && seg.executable() && it->layout->hasSplitSegInfo() ) {
+				// allocate IMPORT segments to end of writable shared region
+				seg.setNewAddress(currentWritableExecutableAddress);
+				currentWritableExecutableAddress += pageAlign(seg.size());
+			}
+		}
+	}	
+
+	// append all LINKEDIT segments at end of all read-only segments
+	fLinkEditsStartAddress = currentReadOnlyAddress;
+	fFirstLinkEditSegment = NULL;
+	for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+		for(int i=0; i < segs.size(); ++i) {
+			MachOLayoutAbstraction::Segment& seg = segs[i];
+			if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") == 0) ) {
+				if ( fFirstLinkEditSegment == NULL ) 
+					fFirstLinkEditSegment = &seg;
+				// allocate non-executable,read-only segments from end of read only shared region
+				seg.setNewAddress(currentReadOnlyAddress);
+				currentReadOnlyAddress += pageAlign(seg.size());
+			}
+		}
+	}
+	fLinkEditsTotalUnoptimizedSize = (currentReadOnlyAddress - fLinkEditsStartAddress + 4095) & (-4096);
+
+
+	// populate large mappings
+	uint64_t cacheFileOffset = 0;
+	if ( currentExecuteAddress > sharedRegionReadOnlyStartAddress() + 0x3000 ) {
+		shared_file_mapping_np  executeMapping;
+		executeMapping.sfm_address		= sharedRegionReadOnlyStartAddress();
+		executeMapping.sfm_size			= currentExecuteAddress - sharedRegionReadOnlyStartAddress();
+		executeMapping.sfm_file_offset	= cacheFileOffset;
+		executeMapping.sfm_max_prot		= VM_PROT_READ | VM_PROT_EXECUTE;
+		executeMapping.sfm_init_prot	= VM_PROT_READ | VM_PROT_EXECUTE;
+		fMappings.push_back(executeMapping);
+		cacheFileOffset += executeMapping.sfm_size;
+		
+		shared_file_mapping_np  writableMapping;
+		writableMapping.sfm_address		= sharedRegionWritableStartAddress();
+		writableMapping.sfm_size		= currentWritableAddress - sharedRegionWritableStartAddress();
+		writableMapping.sfm_file_offset	= cacheFileOffset;
+		writableMapping.sfm_max_prot	= VM_PROT_READ | VM_PROT_WRITE;
+		writableMapping.sfm_init_prot	= VM_PROT_READ | VM_PROT_WRITE;
+		fMappings.push_back(writableMapping);
+		cacheFileOffset += writableMapping.sfm_size;
+		
+		if ( currentWritableExecutableAddress > startWritableExecutableAddress ) {
+			shared_file_mapping_np  writableExecutableMapping;
+			writableExecutableMapping.sfm_address	= startWritableExecutableAddress;
+			writableExecutableMapping.sfm_size		= currentWritableExecutableAddress - startWritableExecutableAddress;
+			writableExecutableMapping.sfm_file_offset= cacheFileOffset;
+			writableExecutableMapping.sfm_max_prot	= VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
+			writableExecutableMapping.sfm_init_prot	= VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE; 
+			fMappings.push_back(writableExecutableMapping);
+			cacheFileOffset += writableExecutableMapping.sfm_size;
+		}
+		
+		// make read-only (contains LINKEDIT segments) last, so it can be cut back when optimized
+		shared_file_mapping_np  readOnlyMapping;
+		readOnlyMapping.sfm_address		= currentExecuteAddress;
+		readOnlyMapping.sfm_size		= currentReadOnlyAddress - currentExecuteAddress;
+		readOnlyMapping.sfm_file_offset	= cacheFileOffset;
+		readOnlyMapping.sfm_max_prot	= VM_PROT_READ;
+		readOnlyMapping.sfm_init_prot	= VM_PROT_READ;
+		fMappings.push_back(readOnlyMapping);
+		cacheFileOffset += readOnlyMapping.sfm_size;
+	}
+	else {
+		// empty cache
+		shared_file_mapping_np  cacheHeaderMapping;
+		cacheHeaderMapping.sfm_address		= sharedRegionWritableStartAddress();
+		cacheHeaderMapping.sfm_size			= 0x3000;
+		cacheHeaderMapping.sfm_file_offset	= cacheFileOffset;
+		cacheHeaderMapping.sfm_max_prot		= VM_PROT_READ;
+		cacheHeaderMapping.sfm_init_prot	= VM_PROT_READ;
+		fMappings.push_back(cacheHeaderMapping);
+		cacheFileOffset += cacheHeaderMapping.sfm_size;
+	}
+}
+
+
+template <typename A>
+uint64_t SharedCache<A>::cacheFileOffsetForAddress(uint64_t addr)
+{
+	for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+		if ( (it->sfm_address <= addr) && (addr < it->sfm_address+it->sfm_size) )
+			return it->sfm_file_offset + addr - it->sfm_address;
+	}
+	throwf("address 0x%0llX is not in cache", addr);
+}
+
+
+template <typename A>
+uint64_t SharedCache<A>::mappedCacheAddressForAddress(uint64_t addr)
+{
+    if (!addr) return 0;
+    else return (uint64_t)(fInMemoryCache + cacheFileOffsetForAddress(addr));
+}
+
+
+template <typename A>
+bool SharedCache<A>::notUpToDate(const void* cache)
+{
+	dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)cache;
+	// not valid if header signature is wrong
+	const char* archPairName = fArchGraph->archName();
+	char temp[16];
+	strcpy(temp, "dyld_v1        ");
+	strcpy(&temp[15-strlen(archPairName)], archPairName);
+	if ( strcmp(header->magic(), temp) != 0 ) {
+		if ( fVerify ) {
+			fprintf(stderr, "update_dyld_shared_cache[%u] cannot verify %s because current cache file has invalid header\n", getpid(), archName());
+			return false;
+		}
+		else {
+			fprintf(stderr, "update_dyld_shared_cache[%u] current cache file has invalid header\n", getpid());
+			return true;
+		}
+	}
+	// not valid if count of images does not match current images needed
+	if ( header->imagesCount() != fDylibs.size() ) {
+		if ( fVerify ) {
+			fprintf(stderr, "update_dyld_shared_cache[%u] cannot verify %s because current cache file contains a different set of dylibs\n", getpid(), archName());
+			return false;
+		}
+		else {
+			fprintf(stderr, "update_dyld_shared_cache[%u] current cache file is invalid because it contains a different set of dylibs\n", getpid());
+			return true;
+		}
+	}
+	// verify every dylib in constructed graph is in existing cache with same inode and modTime	
+	std::map<const MachOLayoutAbstraction*, uint32_t> sortingMap;
+	const dyldCacheImageInfo<E>* imagesStart = (dyldCacheImageInfo<E>*)((uint8_t*)cache + header->imagesOffset());
+	const dyldCacheImageInfo<E>* imagesEnd = &imagesStart[header->imagesCount()];
+	for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		bool found = false;
+		//fprintf(stderr, "inode=0x%llX, mTime=0x%llX, path=%s\n", it->info.inode, it->info.modTime, it->layout->getID().name);
+		for(const dyldCacheImageInfo<E>* cacheEntry = imagesStart; cacheEntry < imagesEnd; ++cacheEntry) {
+			if ( fVerify ) {
+				// in -verify mode, just match by path and warn if file looks different
+				if ( strcmp((char*)cache+cacheEntry->pathFileOffset(), it->layout->getID().name) == 0 ) {
+					found = true;
+					sortingMap[it->layout] = cacheEntry-imagesStart;
+					if ( (cacheEntry->inode() != it->info.inode) || (cacheEntry->modTime() != it->info.modTime) ) {
+						fprintf(stderr, "update_dyld_shared_cache[%u] warning: for arch=%s, %s has changed since cache was built\n", 
+								getpid(), archName(), it->layout->getID().name);
+					}
+					break;
+				}
+			}
+			else {
+				// in normal update mode, everything has to match for cache to be up-to-date
+				if ( (cacheEntry->inode() == it->info.inode) 
+						&& (cacheEntry->modTime() == it->info.modTime) 
+						&& (strcmp((char*)cache+cacheEntry->pathFileOffset(), it->layout->getID().name) == 0) ) {
+					found = true;
+					break;
+				}
+			}
+		}
+		if ( !found ) {
+			if ( fVerify ) {
+				throwf("update_dyld_shared_cache[%u] can't verify %s cache because %s is not in existing cache\n", getpid(), archName(), it->layout->getID().name);
+			}
+			else {
+				fprintf(stderr, "update_dyld_shared_cache[%u] current %s cache file invalid because %s has changed\n", getpid(), archName(), it->layout->getID().name);
+				return true;
+			}
+		}
+	}
+	// all dylibs in existing cache file match those determined need to be in shared cache
+	if ( fVerify ) {
+		// sort fDylibs to match existing cache file so we can compare content
+		std::sort(fDylibs.begin(), fDylibs.end(), Sorter(sortingMap));
+		//fprintf(stderr, "dylibs sorted like existing cache:\n");
+		//for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		//	fprintf(stderr,"   %s\n", it->layout->getID().name);
+		//}
+		// do regenerate a new cache so we can compare content with existing
+		return true;
+	}
+	else {
+		// existing cache file is up-to-date, don't need to regenerate
+		return false;
+	}
+}
+
+
+template <typename A>
+bool SharedCache<A>::notUpToDate(const char* path)
+{
+	// mmap existing cache file 
+	int fd = ::open(path, O_RDONLY);	
+	if ( fd == -1 )
+		return true;
+	struct stat stat_buf;
+	::fstat(fd, &stat_buf);
+	uint8_t* mappingAddr = (uint8_t*)mmap(NULL, stat_buf.st_size, PROT_READ , MAP_FILE | MAP_PRIVATE, fd, 0);
+	::close(fd);
+	if ( mappingAddr == (uint8_t*)(-1) )
+		return true;
+
+	// validate it
+	bool result = this->notUpToDate(mappingAddr);
+	if ( fVerify ) {
+		// don't unmap yet, leave so it can be verified later
+		fExistingCacheForVerification = mappingAddr;
+	}
+	else {
+		// unmap
+		::munmap(mappingAddr, stat_buf.st_size);
+		if ( verbose && !result )
+			fprintf(stderr, "update_dyld_shared_cache: %s is up-to-date\n", path);
+	}
+	return result;
+}
+
+class CStringEquals
+{
+public:
+	bool operator()(const char* left, const char* right) const { return (strcmp(left, right) == 0); }
+};
+
+class StringPool
+{
+public:
+				StringPool();
+	const char*	getBuffer();
+	uint32_t	size();
+	uint32_t	add(const char* str);
+	uint32_t	addUnique(const char* str);
+	const char* stringAtIndex(uint32_t) const;
+private:
+	typedef __gnu_cxx::hash_map<const char*, uint32_t, __gnu_cxx::hash<const char*>, CStringEquals> StringToOffset;
+
+	char*			fBuffer;
+	uint32_t		fBufferAllocated;
+	uint32_t		fBufferUsed;
+	StringToOffset	fUniqueStrings;
+};
+
+
+StringPool::StringPool() 
+	: fBufferUsed(0), fBufferAllocated(32*1024*1024)
+{
+	fBuffer = (char*)malloc(fBufferAllocated);
+}
+
+uint32_t StringPool::add(const char* str)
+{
+	uint32_t len = strlen(str);
+	if ( (fBufferUsed + len + 1) > fBufferAllocated ) {
+		// grow buffer
+		throw "string buffer exhausted";
+	}
+	strcpy(&fBuffer[fBufferUsed], str);
+	uint32_t result = fBufferUsed;
+	fUniqueStrings[&fBuffer[fBufferUsed]] = result;
+	fBufferUsed += len+1;
+	return result;
+}
+
+uint32_t StringPool::addUnique(const char* str)
+{
+	StringToOffset::iterator pos = fUniqueStrings.find(str);
+	if ( pos != fUniqueStrings.end() ) 
+		return pos->second;
+	else {
+		//fprintf(stderr, "StringPool::addUnique() new string: %s\n", str);
+		return this->add(str);
+	}
+}
+
+uint32_t StringPool::size()
+{
+	return fBufferUsed;
+}
+
+const char*	StringPool::getBuffer()
+{
+	return fBuffer;
+}
+
+const char* StringPool::stringAtIndex(uint32_t index) const
+{
+	return &fBuffer[index];
+}
+
+
+template <typename A>
+class LinkEditOptimizer
+{
+public:
+											LinkEditOptimizer(const MachOLayoutAbstraction&, uint8_t*, StringPool&);
+	virtual									~LinkEditOptimizer() {}
+
+		void								copyBindInfo(uint32_t&);
+		void								copyWeakBindInfo(uint32_t&);
+		void								copyLazyBindInfo(uint32_t&);
+		void								copyExportInfo(uint32_t&);
+		void								copyLocalSymbols(uint32_t symbolTableOffset, uint32_t&);
+		void								copyExportedSymbols(uint32_t symbolTableOffset, uint32_t&);
+		void								copyImportedSymbols(uint32_t symbolTableOffset, uint32_t&);
+		void								copyExternalRelocations(uint32_t& offset);
+		void								copyIndirectSymbolTable(uint32_t& offset);
+		void								updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset, 
+																uint32_t linkEditsFileOffset, bool keepSignatures);
+	
+
+protected:
+	typedef typename A::P					P;
+	typedef typename A::P::E				E;
+	typedef typename A::P::uint_t			pint_t;
+			
+private:
+
+	const macho_header<P>*						fHeader; 
+	uint8_t*									fNewLinkEditStart;	
+	uint8_t*									fLinkEditBase;		
+	const MachOLayoutAbstraction&				fLayout;
+	macho_dyld_info_command<P>*					fDyldInfo;
+	macho_dysymtab_command<P>*					fDynamicSymbolTable;
+	macho_symtab_command<P>*					fSymbolTableLoadCommand;
+	const macho_nlist<P>*						fSymbolTable;
+	const char*									fStrings;
+	StringPool&									fNewStringPool;
+	std::map<uint32_t,uint32_t>					fOldToNewSymbolIndexes;
+	uint32_t									fBindInfoOffsetIntoNewLinkEdit;
+	uint32_t									fBindInfoSizeInNewLinkEdit;
+	uint32_t									fWeakBindInfoOffsetIntoNewLinkEdit;
+	uint32_t									fWeakBindInfoSizeInNewLinkEdit;
+	uint32_t									fLazyBindInfoOffsetIntoNewLinkEdit;
+	uint32_t									fLazyBindInfoSizeInNewLinkEdit;
+	uint32_t									fExportInfoOffsetIntoNewLinkEdit;
+	uint32_t									fExportInfoSizeInNewLinkEdit;
+	uint32_t									fSymbolTableStartOffsetInNewLinkEdit;
+	uint32_t									fLocalSymbolsStartIndexInNewLinkEdit;
+	uint32_t									fLocalSymbolsCountInNewLinkEdit;
+	uint32_t									fExportedSymbolsStartIndexInNewLinkEdit;
+	uint32_t									fExportedSymbolsCountInNewLinkEdit;
+	uint32_t									fImportSymbolsStartIndexInNewLinkEdit;
+	uint32_t									fImportedSymbolsCountInNewLinkEdit;
+	uint32_t									fExternalRelocationsOffsetIntoNewLinkEdit;
+	uint32_t									fIndirectSymbolTableOffsetInfoNewLinkEdit;
+};
+
+
+
+template <typename A>
+LinkEditOptimizer<A>::LinkEditOptimizer(const MachOLayoutAbstraction& layout, uint8_t* newLinkEdit, StringPool& stringPool)
+ : 	fLayout(layout), fLinkEditBase(NULL), fNewLinkEditStart(newLinkEdit), fDyldInfo(NULL),
+	fDynamicSymbolTable(NULL), fSymbolTableLoadCommand(NULL), fSymbolTable(NULL), fStrings(NULL), fNewStringPool(stringPool),
+	fBindInfoOffsetIntoNewLinkEdit(0), fBindInfoSizeInNewLinkEdit(0),
+	fWeakBindInfoOffsetIntoNewLinkEdit(0), fWeakBindInfoSizeInNewLinkEdit(0),
+	fLazyBindInfoOffsetIntoNewLinkEdit(0), fLazyBindInfoSizeInNewLinkEdit(0),
+	fExportInfoOffsetIntoNewLinkEdit(0), fExportInfoSizeInNewLinkEdit(0),
+	fSymbolTableStartOffsetInNewLinkEdit(0), 
+	fLocalSymbolsStartIndexInNewLinkEdit(0), fLocalSymbolsCountInNewLinkEdit(0),
+	fExportedSymbolsStartIndexInNewLinkEdit(0), fExportedSymbolsCountInNewLinkEdit(0),
+	fImportSymbolsStartIndexInNewLinkEdit(0), fImportedSymbolsCountInNewLinkEdit(0),
+	fExternalRelocationsOffsetIntoNewLinkEdit(0), fIndirectSymbolTableOffsetInfoNewLinkEdit(0)
+	
+{
+	fHeader = (const macho_header<P>*)fLayout.getSegments()[0].mappedAddress();
+
+	const std::vector<MachOLayoutAbstraction::Segment>& segments = fLayout.getSegments();
+	for(std::vector<MachOLayoutAbstraction::Segment>::const_iterator it = segments.begin(); it != segments.end(); ++it) {
+		const MachOLayoutAbstraction::Segment& seg = *it;
+		if ( strcmp(seg.name(), "__LINKEDIT") == 0 ) 
+			fLinkEditBase = (uint8_t*)seg.mappedAddress() - seg.fileOffset();
+	}
+	if ( fLinkEditBase == NULL )	
+		throw "no __LINKEDIT segment";
+
+	const macho_load_command<P>* const cmds = (macho_load_command<P>*)((uint8_t*)fHeader + sizeof(macho_header<P>));
+	const uint32_t cmd_count = fHeader->ncmds();
+	const macho_load_command<P>* cmd = cmds;
+	for (uint32_t i = 0; i < cmd_count; ++i) {
+		switch (cmd->cmd()) {
+			case LC_SYMTAB:
+				{
+					fSymbolTableLoadCommand = (macho_symtab_command<P>*)cmd;
+					fSymbolTable = (macho_nlist<P>*)(&fLinkEditBase[fSymbolTableLoadCommand->symoff()]);
+					fStrings = (char*)&fLinkEditBase[fSymbolTableLoadCommand->stroff()];
+				}
+				break;
+			case LC_DYSYMTAB:
+				fDynamicSymbolTable = (macho_dysymtab_command<P>*)cmd;
+				break;
+			case LC_DYLD_INFO:
+			case LC_DYLD_INFO_ONLY:
+				fDyldInfo = (macho_dyld_info_command<P>*)cmd;
+				break;
+		}
+		cmd = (const macho_load_command<P>*)(((uint8_t*)cmd)+cmd->cmdsize());
+	}	
+	if ( fSymbolTable == NULL )	
+		throw "no LC_SYMTAB";
+	if ( fDynamicSymbolTable == NULL )	
+		throw "no LC_DYSYMTAB";
+	
+}
+
+
+template <typename A>
+class SymbolSorter
+{
+public:
+	typedef typename A::P P;
+	SymbolSorter(const StringPool& pool) : fStringPool(pool) {}
+	bool operator()(const macho_nlist<P>& left, const macho_nlist<P>& right) { 
+		return (strcmp(fStringPool.stringAtIndex(left.n_strx()) , fStringPool.stringAtIndex(right.n_strx())) < 0); 
+	} 
+	
+private:
+	const StringPool& fStringPool;
+};
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyBindInfo(uint32_t& offset)
+{
+	if ( (fDyldInfo != NULL) && (fDyldInfo->bind_off() != 0) ) {
+		fBindInfoOffsetIntoNewLinkEdit = offset;
+		fBindInfoSizeInNewLinkEdit = fDyldInfo->bind_size();
+		memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->bind_off()], fDyldInfo->bind_size());
+		offset += fDyldInfo->bind_size();
+	}
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyWeakBindInfo(uint32_t& offset)
+{
+	if ( (fDyldInfo != NULL) && (fDyldInfo->weak_bind_off() != 0) ) {
+		fWeakBindInfoOffsetIntoNewLinkEdit = offset;
+		fWeakBindInfoSizeInNewLinkEdit = fDyldInfo->weak_bind_size();
+		memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->weak_bind_off()], fDyldInfo->weak_bind_size());
+		offset += fDyldInfo->weak_bind_size();
+	}
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyLazyBindInfo(uint32_t& offset)
+{
+	if ( (fDyldInfo != NULL) && (fDyldInfo->lazy_bind_off() != 0) ) {
+		fLazyBindInfoOffsetIntoNewLinkEdit = offset;
+		fLazyBindInfoSizeInNewLinkEdit = fDyldInfo->lazy_bind_size();
+		memcpy(fNewLinkEditStart+offset, &fLinkEditBase[fDyldInfo->lazy_bind_off()], fDyldInfo->lazy_bind_size());
+		offset += fDyldInfo->lazy_bind_size();
+	}
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyExportInfo(uint32_t& offset)
+{
+	if ( (fDyldInfo != NULL) && (fDyldInfo->export_off() != 0) ) {
+		fExportInfoOffsetIntoNewLinkEdit = offset;
+		fExportInfoSizeInNewLinkEdit = fDyldInfo->export_size();
+		// warning, export_off is only 32-bits so if the trie grows it must be allocated with 32-bits of fLinkeditBase
+		memcpy(fNewLinkEditStart+offset, fLinkEditBase+(int32_t)fDyldInfo->export_off(), fDyldInfo->export_size());
+		offset += fDyldInfo->export_size();
+	}
+}
+
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyLocalSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex)
+{
+	fLocalSymbolsStartIndexInNewLinkEdit = symbolIndex;
+	fSymbolTableStartOffsetInNewLinkEdit = symbolTableOffset + symbolIndex*sizeof(macho_nlist<P>);
+	macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
+	const macho_nlist<P>* const firstLocal = &fSymbolTable[fDynamicSymbolTable->ilocalsym()];
+	const macho_nlist<P>* const lastLocal  = &fSymbolTable[fDynamicSymbolTable->ilocalsym()+fDynamicSymbolTable->nlocalsym()];
+	uint32_t oldIndex = fDynamicSymbolTable->ilocalsym();
+	for (const macho_nlist<P>* entry = firstLocal; entry < lastLocal; ++entry, ++oldIndex) {
+		if ( (entry->n_type() & N_TYPE) == N_SECT ) {
+			macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
+			*newSymbolEntry = *entry;
+			newSymbolEntry->set_n_strx(fNewStringPool.add(&fStrings[entry->n_strx()]));
+			++symbolIndex;
+		}
+	}
+	fLocalSymbolsCountInNewLinkEdit = symbolIndex - fLocalSymbolsStartIndexInNewLinkEdit;
+	//fprintf(stderr, "%u locals starting at %u for %s\n", fLocalSymbolsCountInNewLinkEdit, fLocalSymbolsStartIndexInNewLinkEdit, fLayout.getFilePath());
+}
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyExportedSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex)
+{
+	fExportedSymbolsStartIndexInNewLinkEdit = symbolIndex;
+	macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
+	const macho_nlist<P>* const firstExport = &fSymbolTable[fDynamicSymbolTable->iextdefsym()];
+	const macho_nlist<P>* const lastExport  = &fSymbolTable[fDynamicSymbolTable->iextdefsym()+fDynamicSymbolTable->nextdefsym()];
+	uint32_t oldIndex = fDynamicSymbolTable->iextdefsym();
+	for (const macho_nlist<P>* entry = firstExport; entry < lastExport; ++entry, ++oldIndex) {
+		if ( ((entry->n_type() & N_TYPE) == N_SECT) && (strncmp(&fStrings[entry->n_strx()], ".objc_", 6) != 0)
+						&& (strncmp(&fStrings[entry->n_strx()], "$ld$", 4) != 0) ) {
+			macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
+			*newSymbolEntry = *entry;
+			newSymbolEntry->set_n_strx(fNewStringPool.add(&fStrings[entry->n_strx()]));
+			fOldToNewSymbolIndexes[oldIndex] = symbolIndex-fLocalSymbolsStartIndexInNewLinkEdit;
+			++symbolIndex;
+		}
+	}
+	fExportedSymbolsCountInNewLinkEdit = symbolIndex - fExportedSymbolsStartIndexInNewLinkEdit;
+	//fprintf(stderr, "%u exports starting at %u for %s\n", fExportedSymbolsCountInNewLinkEdit, fExportedSymbolsStartIndexInNewLinkEdit, fLayout.getFilePath());
+	// sort by name, so that dyld does not need a toc
+	macho_nlist<P>* newSymbolsStart = &newSymbolTableStart[fExportedSymbolsStartIndexInNewLinkEdit];
+	macho_nlist<P>* newSymbolsEnd = &newSymbolTableStart[fExportedSymbolsStartIndexInNewLinkEdit+fExportedSymbolsCountInNewLinkEdit];
+	std::sort(newSymbolsStart, newSymbolsEnd, SymbolSorter<A>(fNewStringPool));
+	//for (macho_nlist<P>* entry = newSymbolsStart; entry < newSymbolsEnd; ++entry)
+	//	fprintf(stderr, "\t%u\t %s\n", (entry-newSymbolsStart)+fExportedSymbolsStartIndexInNewLinkEdit, fNewStringPool.stringAtIndex(entry->n_strx()));
+}
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyImportedSymbols(uint32_t symbolTableOffset, uint32_t& symbolIndex)
+{
+	fImportSymbolsStartIndexInNewLinkEdit = symbolIndex;
+	macho_nlist<P>* const newSymbolTableStart = (macho_nlist<P>*)(fNewLinkEditStart+symbolTableOffset);
+	const macho_nlist<P>* const firstImport = &fSymbolTable[fDynamicSymbolTable->iundefsym()];
+	const macho_nlist<P>* const lastImport  = &fSymbolTable[fDynamicSymbolTable->iundefsym()+fDynamicSymbolTable->nundefsym()];
+	uint32_t oldIndex = fDynamicSymbolTable->iundefsym();
+	for (const macho_nlist<P>* entry = firstImport; entry < lastImport; ++entry, ++oldIndex) {
+		if ( ((entry->n_type() & N_TYPE) == N_UNDF) && (strncmp(&fStrings[entry->n_strx()], ".objc_", 6) != 0) ) {
+			macho_nlist<P>* newSymbolEntry = &newSymbolTableStart[symbolIndex];
+			*newSymbolEntry = *entry;
+			newSymbolEntry->set_n_strx(fNewStringPool.addUnique(&fStrings[entry->n_strx()]));
+			fOldToNewSymbolIndexes[oldIndex] = symbolIndex-fLocalSymbolsStartIndexInNewLinkEdit;
+			++symbolIndex;
+		}
+	}
+	fImportedSymbolsCountInNewLinkEdit = symbolIndex - fImportSymbolsStartIndexInNewLinkEdit;
+	//fprintf(stderr, "%u imports starting at %u for %s\n", fImportedSymbolsCountInNewLinkEdit, fImportSymbolsStartIndexInNewLinkEdit, fLayout.getFilePath());
+	//macho_nlist<P>* newSymbolsStart = &((macho_nlist<P>*)fNewLinkEditStart)[fImportSymbolsStartIndexInNewLinkEdit];
+	//macho_nlist<P>* newSymbolsEnd = &((macho_nlist<P>*)fNewLinkEditStart)[fImportSymbolsStartIndexInNewLinkEdit+fImportedSymbolsCountInNewLinkEdit];
+	//for (macho_nlist<P>* entry = newSymbolsStart; entry < newSymbolsEnd; ++entry)
+	//	fprintf(stderr, "\t%u\t%s\n", (entry-newSymbolsStart)+fImportSymbolsStartIndexInNewLinkEdit, fNewStringPool.stringAtIndex(entry->n_strx()));
+}
+
+
+template <typename A>
+void LinkEditOptimizer<A>::copyExternalRelocations(uint32_t& offset)
+{
+	fExternalRelocationsOffsetIntoNewLinkEdit = offset;
+	const macho_relocation_info<P>* const relocsStart = (macho_relocation_info<P>*)(&fLinkEditBase[fDynamicSymbolTable->extreloff()]);
+	const macho_relocation_info<P>* const relocsEnd = &relocsStart[fDynamicSymbolTable->nextrel()];
+	for (const macho_relocation_info<P>* reloc=relocsStart; reloc < relocsEnd; ++reloc) {
+		macho_relocation_info<P>* newReloc = (macho_relocation_info<P>*)(&fNewLinkEditStart[offset]);
+		*newReloc = *reloc;
+		uint32_t newSymbolIndex = fOldToNewSymbolIndexes[reloc->r_symbolnum()];
+		//fprintf(stderr, "copyExternalRelocations() old=%d, new=%u name=%s in %s\n", reloc->r_symbolnum(), newSymbolIndex,
+		//	 &fStrings[fSymbolTable[reloc->r_symbolnum()].n_strx()], fLayout.getFilePath());
+		newReloc->set_r_symbolnum(newSymbolIndex);
+		offset += sizeof(macho_relocation_info<P>);
+	}
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::copyIndirectSymbolTable(uint32_t& offset)
+{	
+	fIndirectSymbolTableOffsetInfoNewLinkEdit = offset;
+	const uint32_t* const indirectTable = (uint32_t*)&this->fLinkEditBase[fDynamicSymbolTable->indirectsymoff()];
+	uint32_t* newIndirectTable = (uint32_t*)&fNewLinkEditStart[offset];
+	for (int i=0; i < fDynamicSymbolTable->nindirectsyms(); ++i) {
+		uint32_t oldSymbolIndex = E::get32(indirectTable[i]); 
+		uint32_t newSymbolIndex = oldSymbolIndex;
+		if ( (oldSymbolIndex != INDIRECT_SYMBOL_ABS) && (oldSymbolIndex != INDIRECT_SYMBOL_LOCAL) ) {
+			newSymbolIndex = fOldToNewSymbolIndexes[oldSymbolIndex];
+			//fprintf(stderr, "copyIndirectSymbolTable() old=%d, new=%u name=%s in %s\n", oldSymbolIndex, newSymbolIndex,
+			// &fStrings[fSymbolTable[oldSymbolIndex].n_strx()], fLayout.getFilePath());
+		}
+		E::set32(newIndirectTable[i], newSymbolIndex);
+	}
+	offset += (fDynamicSymbolTable->nindirectsyms() * 4);
+}
+
+template <typename A>
+void LinkEditOptimizer<A>::updateLoadCommands(uint64_t newVMAddress, uint64_t size, uint32_t stringPoolOffset, 
+												uint32_t linkEditsFileOffset, bool keepSignatures)
+{
+	// set LINKEDIT segment commmand to new merged LINKEDIT
+	const macho_load_command<P>* const cmds = (macho_load_command<P>*)((uint8_t*)fHeader + sizeof(macho_header<P>));
+	const uint32_t cmd_count = fHeader->ncmds();
+	const macho_load_command<P>* cmd = cmds;
+	for (uint32_t i = 0; i < cmd_count; ++i) {
+		if ( cmd->cmd() == macho_segment_command<P>::CMD ) {
+			macho_segment_command<P>* seg = (macho_segment_command<P>*)cmd;
+			if ( strcmp(seg->segname(), "__LINKEDIT") == 0 ) {
+				seg->set_vmaddr(newVMAddress);
+				seg->set_vmsize(size);
+				seg->set_filesize(size);
+				seg->set_fileoff(linkEditsFileOffset);
+			}
+		}
+		cmd = (const macho_load_command<P>*)(((uint8_t*)cmd)+cmd->cmdsize());
+	}	
+	
+	// update dyld_info with new offsets
+	if ( fDyldInfo != NULL ) {
+		fDyldInfo->set_rebase_off(0);
+		fDyldInfo->set_rebase_size(0);
+		fDyldInfo->set_bind_off(linkEditsFileOffset+fBindInfoOffsetIntoNewLinkEdit);
+		fDyldInfo->set_bind_size(fBindInfoSizeInNewLinkEdit);
+		fDyldInfo->set_weak_bind_off(linkEditsFileOffset+fWeakBindInfoOffsetIntoNewLinkEdit);
+		fDyldInfo->set_weak_bind_size(fWeakBindInfoSizeInNewLinkEdit);
+		fDyldInfo->set_lazy_bind_off(linkEditsFileOffset+fLazyBindInfoOffsetIntoNewLinkEdit);
+		fDyldInfo->set_lazy_bind_size(fLazyBindInfoSizeInNewLinkEdit);
+		fDyldInfo->set_export_off(linkEditsFileOffset+fExportInfoOffsetIntoNewLinkEdit);
+		fDyldInfo->set_export_size(fExportInfoSizeInNewLinkEdit);
+		
+//		fprintf(stderr, "dylib %s\n", fLayout.getFilePath());
+//		fprintf(stderr, "  bind_off=0x%08X\n", fDyldInfo->bind_off());
+//		fprintf(stderr, "  export_off=0x%08X\n", fDyldInfo->export_off());
+//		fprintf(stderr, "  export_size=%d\n", fDyldInfo->export_size());
+		
+	}	
+	
+	// update symbol table and dynamic symbol table with new offsets
+	fSymbolTableLoadCommand->set_symoff(linkEditsFileOffset+fSymbolTableStartOffsetInNewLinkEdit);
+	fSymbolTableLoadCommand->set_nsyms(fLocalSymbolsCountInNewLinkEdit+fExportedSymbolsCountInNewLinkEdit+fImportedSymbolsCountInNewLinkEdit);
+	fSymbolTableLoadCommand->set_stroff(linkEditsFileOffset+stringPoolOffset);
+	fSymbolTableLoadCommand->set_strsize(fNewStringPool.size());
+	fDynamicSymbolTable->set_ilocalsym(0);
+	fDynamicSymbolTable->set_nlocalsym(fLocalSymbolsCountInNewLinkEdit);
+	fDynamicSymbolTable->set_iextdefsym(fExportedSymbolsStartIndexInNewLinkEdit-fLocalSymbolsStartIndexInNewLinkEdit);
+	fDynamicSymbolTable->set_nextdefsym(fExportedSymbolsCountInNewLinkEdit);
+	fDynamicSymbolTable->set_iundefsym(fImportSymbolsStartIndexInNewLinkEdit-fLocalSymbolsStartIndexInNewLinkEdit);
+	fDynamicSymbolTable->set_nundefsym(fImportedSymbolsCountInNewLinkEdit);
+	fDynamicSymbolTable->set_tocoff(0);
+	fDynamicSymbolTable->set_ntoc(0);
+	fDynamicSymbolTable->set_modtaboff(0);
+	fDynamicSymbolTable->set_nmodtab(0);
+	fDynamicSymbolTable->set_indirectsymoff(linkEditsFileOffset+fIndirectSymbolTableOffsetInfoNewLinkEdit);
+	fDynamicSymbolTable->set_extreloff(linkEditsFileOffset+fExternalRelocationsOffsetIntoNewLinkEdit);
+	fDynamicSymbolTable->set_locreloff(0);
+	fDynamicSymbolTable->set_nlocrel(0);
+
+	// now remove load commands no longer needed
+	const macho_load_command<P>* srcCmd = cmds;
+	macho_load_command<P>* dstCmd = (macho_load_command<P>*)cmds;
+	int32_t newCount = 0;
+	for (uint32_t i = 0; i < cmd_count; ++i) {	
+		uint32_t cmdSize = srcCmd->cmdsize();
+		switch ( srcCmd->cmd() ) {
+			case LC_SEGMENT_SPLIT_INFO:
+				// don't copy
+				break;
+			case LC_CODE_SIGNATURE:
+				if ( !keepSignatures )
+					break;
+				// otherwise fall into copy case
+			default:
+				memmove(dstCmd, srcCmd, cmdSize);
+				dstCmd = (macho_load_command<P>*)(((uint8_t*)dstCmd)+cmdSize);
+				++newCount;
+				break;
+		}
+		srcCmd = (const macho_load_command<P>*)(((uint8_t*)srcCmd)+cmdSize);
+	}
+	// zero out stuff removed
+	bzero(dstCmd, (uint8_t*)srcCmd - (uint8_t*)dstCmd);
+	
+	// update mach_header
+	macho_header<P>* writableHeader = (macho_header<P>*)fHeader; 
+	writableHeader->set_ncmds(newCount);
+	writableHeader->set_sizeofcmds((uint8_t*)dstCmd - ((uint8_t*)fHeader + sizeof(macho_header<P>)));
+	
+	// this invalidates some ivars
+	fDynamicSymbolTable = NULL;
+	fSymbolTableLoadCommand = NULL;
+	fDyldInfo = NULL;
+	fSymbolTable = NULL;
+	fStrings = NULL;
+}
+
+
+
+template <typename A>
+uint8_t* SharedCache<A>::optimizeLINKEDIT(bool keepSignatures)
+{
+	// allocate space for optimized LINKEDIT area
+	uint8_t* newLinkEdit = new uint8_t[fLinkEditsTotalUnoptimizedSize];
+	bzero(newLinkEdit, fLinkEditsTotalUnoptimizedSize);
+	
+	// make a string pool 
+	StringPool stringPool;
+	
+	// create optimizer object for each LINKEDIT segment
+	std::vector<LinkEditOptimizer<A>*> optimizers;
+	for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		optimizers.push_back(new LinkEditOptimizer<A>(*it->layout, newLinkEdit, stringPool));
+	}
+
+	// rebase info is not copied because images in shared cache are never rebased
+	
+	// copy weak bind info
+	uint32_t offset = 0;
+	fOffsetOfWeakBindInfoInCombinedLinkedit = offset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyWeakBindInfo(offset);
+	}
+	
+	// copy export info
+	fOffsetOfExportInfoInCombinedLinkedit = offset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyExportInfo(offset);
+	}
+
+	// copy bind info
+	fOffsetOfBindInfoInCombinedLinkedit = offset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyBindInfo(offset);
+	}
+	
+	// copy lazy bind info
+	fOffsetOfLazyBindInfoInCombinedLinkedit = offset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyLazyBindInfo(offset);
+	}
+
+	// copy symbol table entries
+	fOffsetOfOldSymbolTableInfoInCombinedLinkedit = offset;
+	uint32_t symbolTableOffset = offset;
+	uint32_t symbolTableIndex = 0;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyLocalSymbols(symbolTableOffset, symbolTableIndex);
+		(*it)->copyExportedSymbols(symbolTableOffset, symbolTableIndex);
+		(*it)->copyImportedSymbols(symbolTableOffset, symbolTableIndex);
+	}
+	
+	// copy external relocations, 8-byte aligned after end of symbol table
+	uint32_t externalRelocsOffset = symbolTableOffset + (symbolTableIndex * sizeof(macho_nlist<typename A::P>) + 7) & (-8);
+	//uint32_t externalRelocsStartOffset = externalRelocsOffset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyExternalRelocations(externalRelocsOffset);
+	}
+	
+	// copy indirect symbol tables
+	uint32_t indirectSymbolTableOffset = externalRelocsOffset;
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->copyIndirectSymbolTable(indirectSymbolTableOffset);
+	}
+	
+	// copy string pool
+	uint32_t stringPoolOffset = indirectSymbolTableOffset;
+	memcpy(&newLinkEdit[stringPoolOffset], stringPool.getBuffer(), stringPool.size());
+	
+	// find new size
+	fLinkEditsTotalOptimizedSize = (stringPoolOffset + stringPool.size() + 4095) & (-4096);
+	
+	// choose new linkedit file  offset 
+	uint32_t linkEditsFileOffset = fLinkEditsStartAddress - sharedRegionReadOnlyStartAddress();
+	
+	// update load commands so that all dylibs shared different areas of the same LINKEDIT segment
+	for(typename std::vector<LinkEditOptimizer<A>*>::iterator it = optimizers.begin(); it != optimizers.end(); ++it) {
+		(*it)->updateLoadCommands(fLinkEditsStartAddress, fLinkEditsTotalUnoptimizedSize, stringPoolOffset, linkEditsFileOffset, keepSignatures);
+	}
+
+	//fprintf(stderr, "fLinkEditsTotalUnoptimizedSize=%llu, fLinkEditsTotalOptimizedSize=%u\n", fLinkEditsTotalUnoptimizedSize, fLinkEditsTotalOptimizedSize);
+	//printf(stderr, "mega link edit mapped starting at: %p\n", fFirstLinkEditSegment->mappedAddress());
+
+	// overwrite mapped LINKEDIT area with new optimized LINKEDIT segment
+	memcpy(fFirstLinkEditSegment->mappedAddress(), newLinkEdit, fLinkEditsTotalUnoptimizedSize);
+	
+	// update all LINKEDIT Segment objects to point to same merged LINKEDIT area
+	for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+		std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+		for(int i=0; i < segs.size(); ++i) {
+			MachOLayoutAbstraction::Segment& seg = segs[i];
+			if ( !seg.writable() && !seg.executable() && (strcmp(seg.name(), "__LINKEDIT") == 0) ) {
+				seg.setNewAddress(fLinkEditsStartAddress);
+				seg.setMappedAddress(fFirstLinkEditSegment->mappedAddress());
+				seg.setSize(fLinkEditsTotalOptimizedSize);
+				seg.setFileSize(fLinkEditsTotalOptimizedSize);
+				seg.setFileOffset(linkEditsFileOffset);
+			}
+		}
+	}
+	
+	// return new end of cache
+	return (uint8_t*)fFirstLinkEditSegment->mappedAddress() + fLinkEditsTotalOptimizedSize;
+}
+
+
+
+template <typename A>
+class ObjCSelectorUniquer
+{
+private:
+    objc_selopt::string_map fSelectorStrings;
+    SharedCache<A> *fCache;
+    size_t fCount;
+
+public:
+
+    ObjCSelectorUniquer(SharedCache<A> *newCache)
+        : fSelectorStrings()
+        , fCache(newCache)
+        , fCount(0)
+    { }
+
+    typename A::P::uint_t visit(typename A::P::uint_t oldValue) 
+    {
+        fCount++;
+        const char *s = (const char *)
+            fCache->mappedCacheAddressForAddress(oldValue);
+        objc_selopt::string_map::iterator element = 
+            fSelectorStrings.insert(objc_selopt::string_map::value_type(s, oldValue)).first;
+        return (typename A::P::uint_t)element->second;
+    }
+
+    objc_selopt::string_map& strings() { 
+        return fSelectorStrings;
+    }
+
+    size_t count() const { return fCount; }
+};
+
+template <>
+void SharedCache<arm>::optimizeObjC()
+{
+	// objc optimizations on arm not yet supported
+}
+
+template <typename A>
+void SharedCache<A>::optimizeObjC()
+{
+    if ( verbose ) {
+        fprintf(stderr, "update_dyld_shared_cache: for %s, uniquing objc selectors\n", archName());
+    }
+
+    // Find libobjc's __TEXT,__objc_selopt section
+    const macho_section<P> *seloptSection = NULL;
+	for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+        if (0 == strstr(it->layout->getFilePath(), "libobjc")) continue;
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        if ((seloptSection = mh->getSection("__TEXT", "__objc_selopt"))) break;
+	}
+    
+    if (!seloptSection) {
+        warn(archName(), "couldn't find libobjc's unique selector section (selectors not optimized)");
+        return;
+    }
+
+    objc_selopt::objc_selopt_t *seloptData = (objc_selopt::objc_selopt_t *)
+        mappedCacheAddressForAddress(seloptSection->addr());
+    if (seloptSection->size() < sizeof(seloptData->version)) {
+        warn(archName(), "libobjc's unique selector section is too small (selectors not optimized)");
+        return;
+    }
+
+    if (E::get32(seloptData->version) != objc_selopt::VERSION) {
+        warn(archName(), "libobjc's unique selector section version is unrecognized (selectors not optimized)");
+        return;
+    }
+
+
+    // Update selector references and build selector list
+    ObjCSelectorUniquer<A> uniq(this);
+
+    // Heuristic: choose selectors from libraries with more cstring data first.
+    // This tries to localize selector cstring memory.
+    std::vector<LayoutInfo> sortedDylibs = fDylibs;
+    std::sort(sortedDylibs.begin(), sortedDylibs.end(), ByCStringSectionSizeSorter());
+
+	for(typename std::vector<LayoutInfo>::const_iterator it = sortedDylibs.begin(); it != sortedDylibs.end(); ++it) {
+        const macho_header<P> *mh = (const macho_header<P>*)(*it->layout).getSegments()[0].mappedAddress();
+        LegacySelectorUpdater<A, ObjCSelectorUniquer<A> >::update(this, mh, uniq);
+        SelectorUpdater<A, ObjCSelectorUniquer<A> >::update(this, mh, uniq);
+	}
+
+    if ( verbose ) {
+        fprintf(stderr, "update_dyld_shared_cache: for %s, found %zu unique objc selectors\n", archName(), uniq.strings().size());
+    }
+
+    // Write selector hash table to libobjc's __TEXT,__objc_selopt section
+    size_t bytesUsed;
+    const char *err = 
+        objc_selopt::write_selopt(seloptData, seloptSection->addr(), 
+                                  seloptSection->size(), uniq.strings(), 
+                                  E::little_endian, &bytesUsed);
+    if (err) {
+        warn(archName(), err);
+        return;
+    }
+
+    if ( verbose ) {
+        fprintf(stderr, "update_dyld_shared_cache: for %s, %zu/%llu bytes "
+                "(%d%%) used in libobjc unique selector section\n", 
+                archName(), bytesUsed, seloptSection->size(), 
+                (int)(bytesUsed / (double)seloptSection->size() * 100));
+        fprintf(stderr, "update_dyld_shared_cache: for %s, "
+                "updated %zu selector references\n", 
+                archName(), uniq.count());
+    }
+
+    return;
+}
+
+
+static const char* sCleanupFile = NULL;
+static void cleanup(int sig)
+{
+	::signal(sig, SIG_DFL);
+	if ( sCleanupFile != NULL )
+		::unlink(sCleanupFile);
+	//if ( verbose )
+	//	fprintf(stderr, "update_dyld_shared_cache: deleting temp file in response to a signal\n");
+	if ( sig == SIGINT )
+		::exit(1);
+}
+
+
+template <typename A>
+bool SharedCache<A>::update(bool usesOverlay, bool force, bool optimize, bool deleteExistingFirst, int archIndex,
+								int archCount, bool keepSignatures)
+{
+	bool didUpdate = false;
+	
+	// already up to date?
+	if ( force || fExistingIsNotUpToDate ) {
+		if ( verbose )
+			fprintf(stderr, "update_dyld_shared_cache: regenerating %s\n", fCacheFilePath);
+		if ( fDylibs.size() == 0 ) {
+			fprintf(stderr, "update_dyld_shared_cache: warning, empty cache not generated for arch %s\n", archName());
+			return false;
+		}
+		// delete existing cache while building the new one
+		// this is a flag to dyld to stop pinging update_dyld_shared_cache
+		if ( deleteExistingFirst )
+			::unlink(fCacheFilePath);
+		uint8_t* inMemoryCache = NULL;
+		uint32_t allocatedCacheSize = 0;
+		char tempCachePath[strlen(fCacheFilePath)+16];
+		sprintf(tempCachePath, "%s.tmp%u", fCacheFilePath, getpid());
+		try {
+			// allocate a memory block to hold cache
+			uint32_t cacheFileSize = 0;
+			for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+				uint32_t end = it->sfm_file_offset + it->sfm_size;
+				if ( end > cacheFileSize )
+					cacheFileSize = end;
+			}
+			if ( vm_allocate(mach_task_self(), (vm_address_t*)(&inMemoryCache), cacheFileSize, VM_FLAGS_ANYWHERE) != KERN_SUCCESS )
+				throwf("can't vm_allocate cache of size %u", cacheFileSize);
+			allocatedCacheSize = cacheFileSize;
+            fInMemoryCache = inMemoryCache;
+			
+			// fill in header
+			dyldCacheHeader<E>* header = (dyldCacheHeader<E>*)inMemoryCache;
+			const char* archPairName = fArchGraph->archName();
+			char temp[16];
+			strcpy(temp, "dyld_v1        ");
+			strcpy(&temp[15-strlen(archPairName)], archPairName);
+			header->set_magic(temp);
+			//header->set_architecture(arch());
+			header->set_mappingOffset(sizeof(dyldCacheHeader<E>)); 
+			header->set_mappingCount(fMappings.size());
+			header->set_imagesOffset(header->mappingOffset() + fMappings.size()*sizeof(dyldCacheFileMapping<E>));	
+			header->set_imagesCount(fDylibs.size());
+			header->set_dyldBaseAddress(fDyldBaseAddress);
+			//header->set_dependenciesOffset(sizeof(dyldCacheHeader<E>) + fMappings.size()*sizeof(dyldCacheFileMapping<E>) + fDylibs.size()*sizeof(dyldCacheImageInfo<E>));	
+			//header->set_dependenciesCount(fDependencyPool.size());
+			
+			// fill in mappings
+			dyldCacheFileMapping<E>* mapping = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
+			for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: cache mappings: address=0x%0llX, size=0x%0llX, fileOffset=0x%0llX, prot=0x%X\n", 
+									it->sfm_address, it->sfm_size, it->sfm_file_offset, it->sfm_init_prot);
+				mapping->set_address(it->sfm_address);
+				mapping->set_size(it->sfm_size);
+				mapping->set_file_offset(it->sfm_file_offset);
+				mapping->set_max_prot(it->sfm_max_prot);
+				mapping->set_init_prot(it->sfm_init_prot);
+				++mapping;
+			}
+			
+			// fill in image table
+			dyldCacheImageInfo<E>* image = (dyldCacheImageInfo<E>*)mapping;
+			for(typename std::vector<LayoutInfo>::iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+				image->set_address(it->info.address);
+				image->set_modTime(it->info.modTime);
+				image->set_inode(it->info.inode);
+				image->set_pathFileOffset(cacheFileOffsetForAddress(it->info.address+it->info.pathFileOffset));
+				//image->set_dependenciesStartOffset(it->info.dependenciesStartOffset);
+				++image;
+			}
+						
+			// copy each segment to cache buffer
+			const int dylibCount = fDylibs.size();
+			int dylibIndex = 0;
+			int progressIndex = 0;
+			for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++dylibIndex) {
+				const char* path = it->layout->getFilePath();
+				int src = ::open(path, O_RDONLY, 0);
+				if ( src == -1 )
+					throwf("can't open file %s, errnor=%d", it->layout->getID().name, errno);
+				// mark source as "don't cache"
+				(void)fcntl(src, F_NOCACHE, 1);
+				// verify file has not changed since dependency analysis
+				struct stat stat_buf;
+				if ( fstat(src, &stat_buf) == -1)
+					throwf("can't stat open file %s, errno=%d", path, errno);
+				if ( (it->layout->getInode() != stat_buf.st_ino) || (it->layout->getLastModTime() != stat_buf.st_mtime) )
+					throwf("file modified during cache creation: %s", path);
+
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: copying %s to cache\n", it->layout->getID().name);
+				try {
+					const std::vector<MachOLayoutAbstraction::Segment>& segs = it->layout->getSegments();
+					for (int i=0; i < segs.size(); ++i) {
+						const MachOLayoutAbstraction::Segment& seg = segs[i];
+						if ( verbose )
+							fprintf(stderr, "\t\tsegment %s, size=0x%0llX, cache address=0x%0llX\n", seg.name(), seg.fileSize(), seg.newAddress());
+						if ( seg.size() > 0 ) {
+							const uint64_t segmentSrcStartOffset = it->layout->getOffsetInUniversalFile()+seg.fileOffset();
+							const uint64_t segmentSize = seg.fileSize();
+							const uint64_t segmentDstStartOffset = cacheFileOffsetForAddress(seg.newAddress());
+							ssize_t readResult = ::pread(src, &inMemoryCache[segmentDstStartOffset], segmentSize, segmentSrcStartOffset);
+							if ( readResult != segmentSize ) {
+								if ( readResult == -1 )
+									throwf("read failure copying dylib errno=%d for %s", errno, it->layout->getID().name);
+								else
+									throwf("read failure copying dylib. Read of %lld bytes at file offset %lld returned %ld for %s", 
+											segmentSize, segmentSrcStartOffset, readResult, it->layout->getID().name);
+							}
+						}
+					}
+				}
+				catch (const char* msg) {
+					throwf("%s while copying %s to shared cache", msg, it->layout->getID().name);
+				}
+				::close(src);
+				if ( progress ) {
+					// assuming read takes 40% of time
+					int nextProgressIndex = archIndex*100+(40*dylibIndex)/dylibCount;
+					if ( nextProgressIndex != progressIndex )
+						fprintf(stdout, "%3u/%u\n", nextProgressIndex, archCount*100);
+					progressIndex = nextProgressIndex;
+				}
+			}
+						
+			// set mapped address for each segment
+			for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+				std::vector<MachOLayoutAbstraction::Segment>& segs = ((MachOLayoutAbstraction*)(it->layout))->getSegments();
+				for (int i=0; i < segs.size(); ++i) {
+					MachOLayoutAbstraction::Segment& seg = segs[i];
+					if ( seg.size() > 0 )
+						seg.setMappedAddress(inMemoryCache + cacheFileOffsetForAddress(seg.newAddress()));
+					//fprintf(stderr, "%s at %p to %p for %s\n", seg.name(), seg.mappedAddress(), (char*)seg.mappedAddress()+ seg.size(), it->layout->getID().name);
+				}
+			}
+
+			// rebase each dylib in shared cache
+			for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+				try {
+					Rebaser<A> r(*it->layout);
+					r.rebase();
+					//if ( verbose )
+					//	fprintf(stderr, "update_dyld_shared_cache: for %s, rebasing dylib into cache for %s\n", archName(), it->layout->getID().name);
+				}
+				catch (const char* msg) {
+					throwf("%s in %s", msg, it->layout->getID().name);
+				}
+			}
+			
+			// merge/optimize all LINKEDIT segments
+			if ( optimize ) {
+				//fprintf(stderr, "update_dyld_shared_cache: original cache file size %uMB\n", cacheFileSize/(1024*1024));
+				cacheFileSize = (this->optimizeLINKEDIT(keepSignatures) - inMemoryCache);
+				//fprintf(stderr, "update_dyld_shared_cache: optimized cache file size %uMB\n", cacheFileSize/(1024*1024));
+				// update header to reduce mapping size
+				dyldCacheHeader<E>* cacheHeader = (dyldCacheHeader<E>*)inMemoryCache;
+				dyldCacheFileMapping<E>* mappings = (dyldCacheFileMapping<E>*)&inMemoryCache[sizeof(dyldCacheHeader<E>)];
+				dyldCacheFileMapping<E>* lastMapping = &mappings[cacheHeader->mappingCount()-1];
+				lastMapping->set_size(cacheFileSize-lastMapping->file_offset());
+				// update fMappings so .map file will print correctly
+				fMappings.back().sfm_size = cacheFileSize-fMappings.back().sfm_file_offset;
+			}
+			
+			if ( verbose )
+				fprintf(stderr, "update_dyld_shared_cache: for %s, updating binding information for %lu files:\n", archName(), fDylibs.size());
+			// instantiate a Binder for each image and add to map
+			typename Binder<A>::Map map;
+			std::vector<Binder<A>*> binders;
+			for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+				//fprintf(stderr, "binding %s\n", it->layout->getID().name);
+				Binder<A>* binder = new Binder<A>(*it->layout, fDyldBaseAddress);
+				binders.push_back(binder);
+				// only add dylibs to map
+				if ( it->layout->getID().name != NULL )
+					map[it->layout->getID().name] = binder;
+			}
+  			
+			// tell each Binder about the others
+			for(typename std::vector<Binder<A>*>::iterator it = binders.begin(); it != binders.end(); ++it) {
+				(*it)->setDependentBinders(map);
+			}
+			// perform binding
+			for(typename std::vector<Binder<A>*>::iterator it = binders.begin(); it != binders.end(); ++it) {
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: for %s, updating binding information in cache for %s\n", archName(), (*it)->getDylibID());
+				try {
+					(*it)->bind();
+				}
+				catch (const char* msg) {
+					throwf("%s in %s", msg, (*it)->getDylibID());
+				}
+			}
+			// delete binders
+			for(typename std::vector<Binder<A>*>::iterator it = binders.begin(); it != binders.end(); ++it) {
+				delete *it;
+			}
+	
+			// unique objc selectors and update other objc metadata
+            if (optimize) {
+                optimizeObjC();
+            }
+			if ( progress ) {
+				// assuming objc optimizations takes 15% of time
+				fprintf(stdout, "%3u/%u\n", (archIndex+1)*55, archCount*100);
+			}
+
+			if ( fVerify ) {
+				// new cache is built, compare header entries
+				const dyldCacheHeader<E>* newHeader = (dyldCacheHeader<E>*)inMemoryCache;
+				const dyldCacheHeader<E>* oldHeader = (dyldCacheHeader<E>*)fExistingCacheForVerification;
+				if ( newHeader->mappingCount() != oldHeader->mappingCount() ) {
+					throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because caches have a different number of mappings\n",
+					 getpid(), archName());
+				}
+				const dyldCacheFileMapping<E>* newMappings = (dyldCacheFileMapping<E>*)&inMemoryCache[newHeader->mappingOffset()];
+				const dyldCacheFileMapping<E>* oldMappings = (dyldCacheFileMapping<E>*)&fExistingCacheForVerification[oldHeader->mappingOffset()];
+				for (int i=0; i < newHeader->mappingCount(); ++i) {
+					if ( newMappings[i].address() != oldMappings[i].address() ) {
+						throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because mapping %d starts at a different address 0x%0llX vs 0x%0llX\n", 
+							getpid(), archName(), i, newMappings[i].address(), oldMappings[i].address() );
+					}
+					if ( newMappings[i].size() != oldMappings[i].size() ) {
+						throwf("update_dyld_shared_cache[%u] for arch=%s, could not verify cache because mapping %d has a different size\n",
+						 getpid(), archName(), i);
+					}
+				}
+				
+				//fprintf(stderr, "%s existing cache = %p\n", archName(), fExistingCacheForVerification);
+				//fprintf(stderr, "%s new cache = %p\n", archName(), inMemoryCache);
+				// compare content to existing cache page by page
+				for (int offset=0; offset < cacheFileSize; offset += 4096) {
+					if ( memcmp(&inMemoryCache[offset], &fExistingCacheForVerification[offset], 4096) != 0 ) {
+						fprintf(stderr, "verifier found differences on page offset 0x%08X for %s:\n", offset, archName());
+						for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it, ++dylibIndex) {
+							const std::vector<MachOLayoutAbstraction::Segment>& segs = it->layout->getSegments();
+							for(std::vector<MachOLayoutAbstraction::Segment>::const_iterator sit = segs.begin(); sit != segs.end(); ++sit) {
+								const MachOLayoutAbstraction::Segment& seg = *sit;
+								if ( (seg.mappedAddress() <= &inMemoryCache[offset]) && (&inMemoryCache[offset] < ((uint8_t*)seg.mappedAddress() + seg.fileSize())) ) {
+									// all LINKEDITs point to the same region, so just print one
+									if ( strcmp(seg.name(), "__LINKEDIT") == 0 ) 
+										fprintf(stderr, "  in merged LINKEDIT segment\n");
+									else
+										fprintf(stderr, "  in segment %s of dylib %s\n", seg.name(), it->layout->getID().name);
+									break;
+								}
+							}
+						}
+						for (int po=0; po < 4096; po += 16) {
+							if ( memcmp(&inMemoryCache[offset+po], &fExistingCacheForVerification[offset+po], 16) != 0 ) {
+								fprintf(stderr, "   existing: 0x%08X: ", offset+po);
+								for ( int j=0; j < 16; ++j)
+									fprintf(stderr, " 0x%02X", fExistingCacheForVerification[offset+po+j]);
+								fprintf(stderr, "\n");
+								fprintf(stderr, "  should be: 0x%08X: ", offset+po);
+								for ( int j=0; j < 16; ++j)
+									fprintf(stderr, " 0x%02X", inMemoryCache[offset+po+j]);
+								fprintf(stderr, "\n");
+							}
+						}
+					}
+				}
+			}
+			else {
+				// install signal handlers to delete temp file if program is killed 
+				sCleanupFile = tempCachePath;
+				::signal(SIGINT, cleanup);
+				::signal(SIGBUS, cleanup);
+				::signal(SIGSEGV, cleanup);
+				
+				// create var/db/dyld dirs if needed
+				char dyldDirs[1024];
+				strcpy(dyldDirs, fCacheFilePath);
+				char* lastSlash = strrchr(dyldDirs, '/');
+				if ( lastSlash != NULL )
+					lastSlash[1] = '\0';
+				struct stat stat_buf;
+				if ( stat(dyldDirs, &stat_buf) != 0 ) {
+					const char* afterSlash = &dyldDirs[1];
+					char* slash;
+					while ( (slash = strchr(afterSlash, '/')) != NULL ) {
+						*slash = '\0';
+						::mkdir(dyldDirs, S_IRWXU | S_IRGRP|S_IXGRP | S_IROTH|S_IXOTH);
+						*slash = '/';
+						afterSlash = slash+1;
+					}
+				}
+				
+				// create temp file for cache
+				int fd = ::open(tempCachePath, O_CREAT | O_RDWR | O_TRUNC, 0644);	
+				if ( fd == -1 )
+					throwf("can't create temp file %s, errnor=%d", tempCachePath, errno);
+					
+				// try to allocate whole cache file contiguously
+				fstore_t fcntlSpec = { F_ALLOCATECONTIG|F_ALLOCATEALL, F_PEOFPOSMODE, 0, cacheFileSize, 0 };
+				::fcntl(fd, F_PREALLOCATE, &fcntlSpec);
+
+				// write out cache file
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: writing cache to disk\n");
+				if ( ::pwrite(fd, inMemoryCache, cacheFileSize, 0) != cacheFileSize )
+					throwf("write() failure creating cache file, errno=%d", errno);
+				if ( progress ) {
+					// assuming write takes 35% of time
+					fprintf(stdout, "%3u/%u\n", (archIndex+1)*90, archCount*100);
+				}
+				
+				// flush to disk and close
+				int result = ::fcntl(fd, F_FULLFSYNC, NULL);
+				if ( result == -1 ) 
+					fprintf(stderr, "update_dyld_shared_cache: warning, fcntl(F_FULLFSYNC) failed with errno=%d for %s\n", errno, tempCachePath);
+				result = ::close(fd);
+				if ( result != 0 ) 
+					fprintf(stderr, "update_dyld_shared_cache: warning, close() failed with errno=%d for %s\n", errno, tempCachePath);
+				
+				// atomically swap in new cache file, do this after F_FULLFSYNC
+				result = ::rename(tempCachePath, fCacheFilePath);
+				if ( result != 0 ) 
+					throwf("can't swap newly create dyld shared cache file: rename(%s,%s) returned errno=%d", tempCachePath, fCacheFilePath, errno);
+					
+				// flush everything to disk to assure rename() gets recorded
+				::sync();
+				didUpdate = true;
+				
+				// restore default signal handlers
+				::signal(SIGINT, SIG_DFL);
+				::signal(SIGBUS, SIG_DFL);
+				::signal(SIGSEGV, SIG_DFL);
+
+				// generate human readable "map" file that shows the layout of the cache file
+				if ( verbose )
+					fprintf(stderr, "update_dyld_shared_cache: writing .map file to disk\n");
+				char mapFilePath[strlen(fCacheFilePath)+16];
+				sprintf(mapFilePath, "%s.map", fCacheFilePath);
+				char tempMapFilePath[strlen(fCacheFilePath)+32];
+				sprintf(tempMapFilePath, "%s.map%u", fCacheFilePath, getpid());
+				FILE* fmap = ::fopen(tempMapFilePath, "w");	
+				if ( fmap == NULL ) {
+					fprintf(stderr, "can't create map file %s, errnor=%d", tempCachePath, errno);
+				}
+				else {
+					for(std::vector<shared_file_mapping_np>::iterator it = fMappings.begin(); it != fMappings.end(); ++it) {
+						const char* prot = "RW";
+						if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_READ) )
+							prot = "EX";
+						else if ( it->sfm_init_prot == VM_PROT_READ )
+							prot = "RO";
+						else if ( it->sfm_init_prot == (VM_PROT_EXECUTE|VM_PROT_WRITE|VM_PROT_READ) )
+							prot = "WX";
+						if ( it->sfm_size > 1024*1024 )
+							fprintf(fmap, "mapping %s %4lluMB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/(1024*1024),
+																it->sfm_address, it->sfm_address+it->sfm_size);
+						else
+							fprintf(fmap, "mapping %s %4lluKB 0x%0llX -> 0x%0llX\n", prot, it->sfm_size/1024,
+																it->sfm_address, it->sfm_address+it->sfm_size);
+					}
+
+					fprintf(fmap, "linkedit   %4uKB 0x%0llX -> 0x%0llX weak binding info\n",		
+								(fOffsetOfExportInfoInCombinedLinkedit-fOffsetOfWeakBindInfoInCombinedLinkedit)/1024,
+								fLinkEditsStartAddress+fOffsetOfWeakBindInfoInCombinedLinkedit,
+								fLinkEditsStartAddress+fOffsetOfExportInfoInCombinedLinkedit);
+					fprintf(fmap, "linkedit   %4uKB 0x%0llX -> 0x%0llX export info\n",		
+								(fOffsetOfBindInfoInCombinedLinkedit-fOffsetOfExportInfoInCombinedLinkedit)/1024,
+								fLinkEditsStartAddress+fOffsetOfExportInfoInCombinedLinkedit,
+								fLinkEditsStartAddress+fOffsetOfBindInfoInCombinedLinkedit);
+					fprintf(fmap, "linkedit   %4uKB 0x%0llX -> 0x%0llX binding info\n",		
+								(fOffsetOfLazyBindInfoInCombinedLinkedit-fOffsetOfBindInfoInCombinedLinkedit)/1024,
+								fLinkEditsStartAddress+fOffsetOfBindInfoInCombinedLinkedit,
+								fLinkEditsStartAddress+fOffsetOfLazyBindInfoInCombinedLinkedit);
+					fprintf(fmap, "linkedit   %4uKB 0x%0llX -> 0x%0llX lazy binding info\n",		
+								(fOffsetOfOldSymbolTableInfoInCombinedLinkedit-fOffsetOfLazyBindInfoInCombinedLinkedit)/1024,
+								fLinkEditsStartAddress+fOffsetOfLazyBindInfoInCombinedLinkedit,
+								fLinkEditsStartAddress+fOffsetOfOldSymbolTableInfoInCombinedLinkedit);
+					fprintf(fmap, "linkedit   %4uMB 0x%0llX -> 0x%0llX non-dyld symbol table info\n",		
+								(fLinkEditsTotalOptimizedSize-fOffsetOfOldSymbolTableInfoInCombinedLinkedit)/(1024*1024),
+								fLinkEditsStartAddress+fOffsetOfOldSymbolTableInfoInCombinedLinkedit,
+								fLinkEditsStartAddress+fLinkEditsTotalOptimizedSize);				
+					
+					for(typename std::vector<LayoutInfo>::const_iterator it = fDylibs.begin(); it != fDylibs.end(); ++it) {
+						fprintf(fmap, "%s\n", it->layout->getID().name);
+						const std::vector<MachOLayoutAbstraction::Segment>&	segs = it->layout->getSegments();
+						for (int i=0; i < segs.size(); ++i) {
+							const MachOLayoutAbstraction::Segment& seg = segs[i];
+							fprintf(fmap, "\t%16s 0x%0llX -> 0x%0llX\n", seg.name(), seg.newAddress(), seg.newAddress()+seg.size());
+						}
+					}
+					if ( warnings.size() > 0 ) {
+						fprintf(fmap, "# Warnings:\n");
+						for (std::vector<const char*>::iterator it=warnings.begin(); it != warnings.end(); ++it) {
+							fprintf(fmap, "# %s\n", *it);
+						}
+					}
+					fclose(fmap);
+					result = ::rename(tempMapFilePath, mapFilePath);
+				}
+			}
+			
+			// free in memory cache
+			vm_deallocate(mach_task_self(), (vm_address_t)inMemoryCache, allocatedCacheSize);
+			inMemoryCache = NULL;
+			if ( progress ) {
+				// finished
+				fprintf(stdout, "%3u/%u\n", (archIndex+1)*100, archCount*100);
+			}
+		}
+		catch (...){
+			// remove temp cache file
+			::unlink(tempCachePath);
+			// remove in memory cache
+			if ( inMemoryCache != NULL ) 
+				vm_deallocate(mach_task_self(), (vm_address_t)inMemoryCache, allocatedCacheSize);
+			throw;
+		}
+	}
+	return didUpdate;
+}
+
+
+
+//
+//	The shared cache is driven by /var/db/dyld/shared_region_roots which contains
+//	the paths used to search for dylibs that should go in the shared cache  
+//
+//	Leading and trailing white space is ignored
+//	Blank lines are ignored
+//	Lines starting with # are ignored
+//
+static void parsePathsFile(const char* filePath, std::vector<const char*>& paths)
+{
+	// read in whole file
+	int fd = open(filePath, O_RDONLY, 0);
+	if ( fd == -1 ) {
+		fprintf(stderr, "update_dyld_shared_cache: can't open file: %s\n", filePath);
+		exit(1);
+	}
+	struct stat stat_buf;
+	fstat(fd, &stat_buf);
+	char* p = (char*)malloc(stat_buf.st_size);
+	if ( p == NULL ) {
+		fprintf(stderr, "update_dyld_shared_cache: malloc failure\n");
+		exit(1);
+	}	
+	if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size ) {
+		fprintf(stderr, "update_dyld_shared_cache: can't read file: %s\n", filePath);
+		exit(1);
+	}	
+	::close(fd);
+	
+	// parse into paths and add to vector
+	char * const end = &p[stat_buf.st_size];
+	enum { lineStart, inSymbol, inComment } state = lineStart;
+	char* symbolStart = NULL;
+	for (char* s = p; s < end; ++s ) {
+		switch ( state ) {
+			case lineStart:
+				if ( *s =='#' ) {
+					state = inComment;
+				}
+				else if ( !isspace(*s) ) {
+					state = inSymbol;
+					symbolStart = s;
+				}
+				break;
+			case inSymbol:
+				if ( *s == '\n' ) {
+					*s = '\0';
+					// removing any trailing spaces
+					char* last = s-1;
+					while ( isspace(*last) ) {
+						*last = '\0';
+						--last;
+					}
+					paths.push_back(symbolStart);
+					symbolStart = NULL;
+					state = lineStart;
+				}
+				break;
+			case inComment:
+				if ( *s == '\n' )
+					state = lineStart;
+				break;
+		}
+	}
+	// Note: we do not free() the malloc buffer, because the strings in it are used by exec()
+}
+
+
+
+static void setSharedDylibs(const char* rootPath, bool usesOverlay, const std::set<ArchPair>& onlyArchs, std::vector<const char*> rootsPaths)
+{
+	// set file system root
+	ArchGraph::setFileSystemRoot(rootPath, usesOverlay);
+
+	// initialize all architectures requested
+	for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
+		ArchGraph::addArchPair(*a);
+
+	// add roots to graph
+	for(std::vector<const char*>::const_iterator it = rootsPaths.begin(); it != rootsPaths.end(); ++it) 
+		ArchGraph::addRoot(*it, onlyArchs);
+
+	// determine shared dylibs
+	for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a)
+		ArchGraph::findSharedDylibs(*a);
+}
+
+
+static void scanForSharedDylibs(const char* rootPath, bool usesOverlay, const char* dirOfPathFiles, const std::set<ArchPair>& onlyArchs)
+{
+	char rootDirOfPathFiles[strlen(rootPath)+strlen(dirOfPathFiles)+2];
+	// in -overlay mode, still look for roots in /var/db/dyld
+	// in -root mode, look for roots in /rootpath/var/db/dyld
+	if ( !usesOverlay && (strlen(rootPath) != 0) ) {
+		strcpy(rootDirOfPathFiles, rootPath);
+		strcat(rootDirOfPathFiles, dirOfPathFiles);
+		dirOfPathFiles = rootDirOfPathFiles;
+	}
+
+	// extract all root paths from files in "/var/db/dyld/shared_region_roots/"
+	if ( verbose )
+		fprintf(stderr, "update_dyld_shared_cache: finding roots in: %s\n", dirOfPathFiles);
+	std::vector<const char*> rootsPaths;
+	DIR* dir = ::opendir(dirOfPathFiles);
+	if ( dir == NULL )
+		throwf("%s does not exist, errno=%d\n", dirOfPathFiles, errno);
+	for (dirent* entry = ::readdir(dir); entry != NULL; entry = ::readdir(dir)) {
+		if ( entry->d_type == DT_REG ) {
+			// only look at files ending in .paths
+			if ( strcmp(&entry->d_name[entry->d_namlen-6], ".paths") == 0 ) {
+				char fullPath[strlen(dirOfPathFiles)+entry->d_namlen+2];
+				strcpy(fullPath, dirOfPathFiles);
+				strcat(fullPath, "/");
+				strcat(fullPath, entry->d_name);
+				parsePathsFile(fullPath, rootsPaths);
+			}
+			else {
+				fprintf(stderr, "update_dyld_shared_cache: warning, ignore file with wrong extension: %s\n", entry->d_name);
+			}
+		}
+	}
+	::closedir(dir);
+	
+	if ( rootsPaths.size() == 0 )
+		fprintf(stderr, "update_dyld_shared_cache: warning, no entries found in shared_region_roots\n");
+	setSharedDylibs(rootPath, usesOverlay, onlyArchs, rootsPaths);
+}
+
+static void setSharedDylibs(const char* rootPath, bool usesOverlay, const char* pathsFile, const std::set<ArchPair>& onlyArchs)
+{
+	std::vector<const char*> rootsPaths;
+	parsePathsFile(pathsFile, rootsPaths);
+	setSharedDylibs(rootPath, usesOverlay, onlyArchs, rootsPaths);
+}
+
+
+// If the 10.5.0 version of update_dyld_shared_cache was killed or crashed, it 
+// could leave large half written cache files laying around.  The function deletes
+// those files.  To prevent the deletion of tmp files being created by another
+// copy of update_dyld_shared_cache, it only deletes the temp cache file if its 
+// creation time was before the last restart of this machine.
+static void deleteOrphanTempCacheFiles()
+{
+	DIR* dir = ::opendir(DYLD_SHARED_CACHE_DIR);
+	if ( dir != NULL ) {
+		std::vector<const char*> filesToDelete;
+		for (dirent* entry = ::readdir(dir); entry != NULL; entry = ::readdir(dir)) {
+			if ( entry->d_type == DT_REG ) {
+				// only look at files with .tmp in name
+				if ( strstr(entry->d_name, ".tmp") != NULL ) {
+					char fullPath[strlen(DYLD_SHARED_CACHE_DIR)+entry->d_namlen+2];
+					strcpy(fullPath, DYLD_SHARED_CACHE_DIR);
+					strcat(fullPath, "/");
+					strcat(fullPath, entry->d_name);
+					struct stat tmpFileStatInfo;
+					if ( stat(fullPath, &tmpFileStatInfo) != -1 ) {
+						int mib[2] = {CTL_KERN, KERN_BOOTTIME};
+						struct timeval boottime;
+						size_t size = sizeof(boottime);
+						if ( (sysctl(mib, 2, &boottime, &size, NULL, 0) != -1) && (boottime.tv_sec != 0) ) {	
+							// make sure this file is older than the boot time of this machine
+							if ( tmpFileStatInfo.st_mtime < boottime.tv_sec ) {
+								filesToDelete.push_back(strdup(fullPath));
+							}
+						}
+					}
+				}
+			}
+		}
+		::closedir(dir);
+		for(std::vector<const char*>::iterator it = filesToDelete.begin(); it != filesToDelete.end(); ++it) {
+			fprintf(stderr, "update_dyld_shared_cache: deleting old temp cache file: %s\n", *it);
+			::unlink(*it);
+		}
+	}
+}
+
+
+
+static bool updateSharedeCacheFile(const char* rootPath, bool usesOverlay, const char* cacheDir, const std::set<ArchPair>& onlyArchs, 
+									bool force, bool alphaSort, bool optimize, bool deleteExistingFirst, bool verify, bool keepSignatures)
+{
+	bool didUpdate = false;
+	// get dyld load address info
+	UniversalMachOLayout* dyldLayout = NULL;
+	char dyldPath[1024];
+	strlcpy(dyldPath, rootPath, 1024);
+	strlcat(dyldPath, "/usr/lib/dyld", 1024);
+	struct stat stat_buf;
+	if ( stat(dyldPath, &stat_buf) == 0 ) {
+		dyldLayout = new UniversalMachOLayout(dyldPath, &onlyArchs);
+	}
+	else {
+		dyldLayout = new UniversalMachOLayout("/usr/lib/dyld", &onlyArchs);
+	}
+	const int archCount = onlyArchs.size();
+	int index = 0;
+	for(std::set<ArchPair>::iterator a = onlyArchs.begin(); a != onlyArchs.end(); ++a, ++index) {
+		const MachOLayoutAbstraction* dyldLayoutForArch = dyldLayout->getSlice(*a);
+		uint64_t dyldBaseAddress = 0;
+		if ( dyldLayoutForArch != NULL )
+			dyldBaseAddress = dyldLayoutForArch->getBaseAddress();
+		else
+			fprintf(stderr, "update_dyld_shared_cache: warning, dyld not available for specified architectures\n");
+		switch ( a->arch ) {
+			case CPU_TYPE_POWERPC:
+				{
+		#if __i386__ || __x86_64__
+					// <rdar://problem/5217377> Rosetta does not work with optimized dyld shared cache
+					SharedCache<ppc> cache(ArchGraph::graphForArchPair(*a), rootPath, alphaSort, verify, false, usesOverlay, dyldBaseAddress);
+					didUpdate |= cache.update(usesOverlay, force, false, deleteExistingFirst, index, archCount, keepSignatures);
+		#else
+					SharedCache<ppc> cache(ArchGraph::graphForArchPair(*a), rootPath, alphaSort, verify, optimize, usesOverlay, dyldBaseAddress);
+					didUpdate |= cache.update(usesOverlay, force, optimize, deleteExistingFirst, index, archCount, keepSignatures);
+		#endif
+				}
+				break;
+			case CPU_TYPE_I386:
+				{
+					SharedCache<x86> cache(ArchGraph::graphForArchPair(*a), rootPath, alphaSort, verify, optimize, usesOverlay, dyldBaseAddress);
+					didUpdate |= cache.update(usesOverlay, force, optimize, deleteExistingFirst, index, archCount, keepSignatures);
+				}
+				break;
+			case CPU_TYPE_X86_64:
+				{
+					SharedCache<x86_64> cache(ArchGraph::graphForArchPair(*a), rootPath, alphaSort, verify, optimize, usesOverlay, dyldBaseAddress);
+					didUpdate |= cache.update(usesOverlay, force, optimize, deleteExistingFirst, index, archCount, keepSignatures);
+				}
+				break;
+			case CPU_TYPE_ARM:
+				{
+					SharedCache<arm> cache(ArchGraph::graphForArchPair(*a), rootPath, alphaSort, verify, optimize, usesOverlay, dyldBaseAddress);
+					didUpdate |= cache.update(usesOverlay, force, optimize, deleteExistingFirst, index, archCount, keepSignatures);
+				}
+				break;
+		}
+	}
+	
+	deleteOrphanTempCacheFiles();
+	
+	return didUpdate;
+}
+
+
+static void usage()
+{
+	fprintf(stderr, "update_dyld_shared_cache [-force] [-root dir] [-overlay dir] [-arch arch] [-debug]\n");
+}
+
+
+int main(int argc, const char* argv[])
+{
+	std::set<ArchPair> onlyArchs;
+	const char* rootPath = "";
+	const char* dylibListFile = NULL;
+	bool force = false;
+	bool alphaSort = false;
+	bool optimize = true;
+	bool hasRoot = false;
+	bool hasOverlay = false;
+	bool verify = false;
+	bool keepSignatures = false;
+	
+	try {
+		// parse command line options
+		for(int i=1; i < argc; ++i) {
+			const char* arg = argv[i];
+			if ( arg[0] == '-' ) {
+				if ( strcmp(arg, "-debug") == 0 ) {
+					verbose = true;
+				}
+				else if ( strcmp(arg, "-force") == 0 ) {
+					force = true;
+				}
+				else if ( strcmp(arg, "-verify") == 0 ) {
+					verify = true;
+				}
+				else if ( strcmp(arg, "-sort_by_name") == 0 ) {
+					alphaSort = true;
+				}
+				else if ( strcmp(arg, "-progress") == 0 ) {
+					progress = true;
+				}
+				else if ( strcmp(arg, "-opt") == 0 ) {
+					optimize = true;
+				}
+				else if ( strcmp(arg, "-no_opt") == 0 ) {
+					optimize = false;
+				}
+				else if ( strcmp(arg, "-dylib_list") == 0 ) {
+					dylibListFile = argv[++i];
+					if ( dylibListFile == NULL )
+						throw "-dylib_list missing path argument";
+					keepSignatures = true;
+				}
+				else if ( (strcmp(arg, "-root") == 0) || (strcmp(arg, "--root") == 0) ) {
+					if ( hasOverlay )
+						throw "cannot use both -root and -overlay";
+					rootPath = argv[++i];
+					if ( rootPath == NULL )
+						throw "-root missing path argument";
+					hasRoot = true;
+				}
+				else if ( strcmp(arg, "-overlay") == 0 ) {
+					if ( hasRoot )
+						throw "cannot use both -root and -overlay";
+					rootPath = argv[++i];
+					if ( rootPath == NULL )
+						throw "-root missing path argument";
+					hasOverlay = true;
+				}
+				else if ( strcmp(arg, "-arch") == 0 ) {
+					const char* arch = argv[++i];
+					if ( strcmp(arch, "ppc") == 0 ) 
+						onlyArchs.insert(ArchPair(CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL));
+					else if ( strcmp(arch, "i386") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
+					else if ( strcmp(arch, "x86_64") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
+					else if ( strcmp(arch, "armv4t") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V4T));
+					else if ( strcmp(arch, "armv5") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V5TEJ));
+					else if ( strcmp(arch, "armv6") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V6));
+					else if ( strcmp(arch, "armv7") == 0 )
+						onlyArchs.insert(ArchPair(CPU_TYPE_ARM, CPU_SUBTYPE_ARM_V7));
+					else 
+						throwf("unknown architecture %s", arch);
+				}
+				else if ( strcmp(arg, "-universal_boot") == 0 ) {
+			#if __ppc__
+					throwf("universal_boot option can only be used on Intel machines");
+			#endif
+					onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
+					onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
+				}
+				else {
+					usage();
+					throwf("unknown option: %s\n", arg);
+				}
+			}
+			else {
+				usage();
+				throwf("unknown option: %s\n", arg);
+			}
+		}
+				
+		// strip tailing slashes on -root or -overlay
+		if ( rootPath[0] != '\0' ) {
+			int len = strlen(rootPath)-1;
+			if (  rootPath[len] == '/' ) {
+				char* newRootPath = strdup(rootPath);
+				while ( newRootPath[len] == '/' )	
+					newRootPath[len--] = '\0';
+				rootPath = newRootPath;
+			}
+		}
+		
+		// if no restrictions specified, use architectures that work on this machine
+		if ( onlyArchs.size() == 0 ) {
+			int available;
+			size_t len = sizeof(int);
+		#if __i386__ || __x86_64__
+			onlyArchs.insert(ArchPair(CPU_TYPE_I386, CPU_SUBTYPE_I386_ALL));
+			// check rosetta is installed
+			char rosettaPath[1024];
+			strlcpy(rosettaPath, rootPath, 1024);
+			strlcat(rosettaPath, "/usr/libexec/oah/translate", 1024);
+			struct stat stat_buf;
+			if ( stat(rosettaPath, &stat_buf) == 0 ) {
+				onlyArchs.insert(ArchPair(CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL));
+			}
+			else if ( hasOverlay ) {
+				// in overlay mode, rosetta may be installed on base system, but is not in update root
+				if ( stat("/usr/libexec/oah/translate", &stat_buf) == 0 ) 
+					onlyArchs.insert(ArchPair(CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL));
+			}
+			// check system is capable of running 64-bit programs
+			if ( (sysctlbyname("hw.optional.x86_64", &available, &len, NULL, 0) == 0) && available )
+				onlyArchs.insert(ArchPair(CPU_TYPE_X86_64, CPU_SUBTYPE_X86_64_ALL));
+		#else
+			#error unknown architecture
+		#endif
+		}
+		
+		if ( !verify && (geteuid() != 0) )
+			throw "you must be root to run this tool";
+		
+		// build list of shared dylibs
+		if ( dylibListFile != NULL )
+			setSharedDylibs(rootPath, hasOverlay, dylibListFile, onlyArchs);
+		else
+			scanForSharedDylibs(rootPath, hasOverlay, "/var/db/dyld/shared_region_roots/", onlyArchs);
+		updateSharedeCacheFile(rootPath, hasOverlay, DYLD_SHARED_CACHE_DIR, onlyArchs, force, alphaSort, optimize, 
+								false, verify, keepSignatures);
+	}
+	catch (const char* msg) {
+		fprintf(stderr, "update_dyld_shared_cache failed: %s\n", msg);
+		return 1;
+	}
+	
+	return 0;
+}
+
+
+