ROM loading cleanup:

* More flexible constructors for path_iterator and emu_file
* More straightforward system/device ROM loading and software loading when using ROM loader
* Proper parent walk when searching for identical CHDs with different names from software list
* Fixed hangs if software item parents form a loop
* Fixed layouts being loaded from bogus empty paths

Note that there are changes in behaviour:
* For software list ROMs/disks, MAME will now search the software path before searching the machine path
* The search path for the owner of the software list device is used, which may not be the driver itself
* MAME will no longer load loose CHDs from the media path - it's just too unwieldy with the number of supported systems
* MAME will no longer search archives above the top level of the media path

15 files changed, 764 insertions, 607 deletions

diff --git a/src/emu/diimage.cpp b/src/emu/diimage.cpp
index 8cc849ee189..4ec5ff7898c 100644
--- a/src/emu/diimage.cpp
+++ b/src/emu/diimage.cpp
@@ -836,56 +836,44 @@ std::vector<u32> device_image_interface::determine_open_plan(bool is_create)
 
 
 //-------------------------------------------------
-//  dump_wrong_and_correct_checksums - dump an
-//  error message containing the wrong and the
-//  correct checksums for a given software item
-//-------------------------------------------------
-
-static void dump_wrong_and_correct_checksums(const util::hash_collection &hashes, const util::hash_collection &acthashes)
-{
-	osd_printf_error("    EXPECTED: %s\n", hashes.macro_string());
-	osd_printf_error("       FOUND: %s\n", acthashes.macro_string());
-}
-
-
-//-------------------------------------------------
 //  verify_length_and_hash - verify the length
 //  and hash signatures of a file
 //-------------------------------------------------
 
 static int verify_length_and_hash(emu_file *file, const char *name, u32 explength, const util::hash_collection &hashes)
 {
-	int retVal = 0;
-	if (file==nullptr) return 0;
+	int retval = 0;
+	if (!file)
+		return 0;
 
 	// verify length
 	u32 actlength = file->size();
 	if (explength != actlength)
 	{
 		osd_printf_error("%s WRONG LENGTH (expected: %d found: %d)\n", name, explength, actlength);
-		retVal++;
+		retval++;
 	}
 
-	// If there is no good dump known, write it
 	util::hash_collection &acthashes = file->hashes(hashes.hash_types().c_str());
 	if (hashes.flag(util::hash_collection::FLAG_NO_DUMP))
 	{
+		// If there is no good dump known, write it
 		osd_printf_error("%s NO GOOD DUMP KNOWN\n", name);
 	}
-	// verify checksums
 	else if (hashes != acthashes)
 	{
 		// otherwise, it's just bad
 		osd_printf_error("%s WRONG CHECKSUMS:\n", name);
-		dump_wrong_and_correct_checksums(hashes, acthashes);
-		retVal++;
+		osd_printf_error("    EXPECTED: %s\n", hashes.macro_string());
+		osd_printf_error("       FOUND: %s\n", acthashes.macro_string());
+		retval++;
 	}
-	// If it matches, but it is actually a bad dump, write it
 	else if (hashes.flag(util::hash_collection::FLAG_BAD_DUMP))
 	{
+		// If it matches, but it is actually a bad dump, write it
 		osd_printf_error("%s NEEDS REDUMP\n",name);
 	}
-	return retVal;
+	return retval;
 }
 
 
@@ -895,102 +883,91 @@ static int verify_length_and_hash(emu_file *file, const char *name, u32 explengt
 
 bool device_image_interface::load_software(software_list_device &swlist, const char *swname, const rom_entry *start)
 {
-	std::string locationtag, breakstr("%");
-	const rom_entry *region;
-	bool retVal = false;
+	bool retval = false;
 	int warningcount = 0;
-	for (region = start; region != nullptr; region = rom_next_region(region))
+	for (const rom_entry *region = start; region; region = rom_next_region(region))
 	{
 		// loop until we hit the end of this region
-		const rom_entry *romp = region + 1;
-		while (!ROMENTRY_ISREGIONEND(romp))
+		for (const rom_entry *romp = region + 1; !ROMENTRY_ISREGIONEND(romp); romp++)
 		{
 			// handle files
 			if (ROMENTRY_ISFILE(romp))
 			{
-				osd_file::error filerr = osd_file::error::NOT_FOUND;
-
-				u32 crc = 0;
-				bool has_crc = util::hash_collection(ROM_GETHASHDATA(romp)).crc(crc);
-
-				const software_info *swinfo = swlist.find(swname);
-				if (swinfo == nullptr)
+				const software_info *const swinfo = swlist.find(swname);
+				if (!swinfo)
 					return false;
 
-				u32 supported = swinfo->supported();
+				const u32 supported = swinfo->supported();
 				if (supported == SOFTWARE_SUPPORTED_PARTIAL)
 					osd_printf_error("WARNING: support for software %s (in list %s) is only partial\n", swname, swlist.list_name());
 				if (supported == SOFTWARE_SUPPORTED_NO)
 					osd_printf_error("WARNING: support for software %s (in list %s) is only preliminary\n", swname, swlist.list_name());
 
-				// attempt reading up the chain through the parents and create a locationtag std::string in the format
-				// " swlist % clonename % parentname "
-				// below, we have the code to split the elements and to create paths to load from
+				u32 crc = 0;
+				const bool has_crc = util::hash_collection(ROM_GETHASHDATA(romp)).crc(crc);
+				std::vector<const software_info *> parents;
+				std::vector<std::string> searchpath;
 
-				while (swinfo != nullptr)
+				// search <rompath>/<list>/<software> following parents
+				searchpath.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), swname));
+				for (const software_info *i = swinfo; i && !i->parentname().empty(); i = swlist.find(i->parentname()))
 				{
-					locationtag.append(swinfo->shortname()).append(breakstr);
-					swinfo = !swinfo->parentname().empty() ? swlist.find(swinfo->parentname()) : nullptr;
+					if (std::find(parents.begin(), parents.end(), i) != parents.end())
+					{
+						osd_printf_warning("WARNING: parent/clone relationships form a loop for software %s (in list %s)\n", swname, swlist.list_name());
+						break;
+					}
+					parents.emplace_back(i);
+					searchpath.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), i->parentname()));
 				}
-				// strip the final '%'
-				locationtag.erase(locationtag.length() - 1, 1);
 
+				// search <rompath>/<software> following parents
+				searchpath.emplace_back(swname);
+				parents.clear();
+				for (software_info const *i = swinfo; i && !i->parentname().empty(); i = swlist.find(i->parentname()))
+				{
+					if (std::find(parents.begin(), parents.end(), i) != parents.end())
+						break;
+					parents.emplace_back(i);
+					searchpath.emplace_back(i->parentname());
+				}
 
-				// check if locationtag actually contains two locations separated by '%'
-				// (i.e. check if we are dealing with a clone in softwarelist)
-				std::string tag2, tag3, tag4(locationtag), tag5;
-				int separator = tag4.find_first_of('%');
-				if (separator != -1)
+				// for historical reasons, add the search path for the software list device's owner
+				const device_t *const listowner = swlist.owner();
+				if (listowner)
 				{
-					// we are loading a clone through softlists, split the setname from the parentname
-					tag5.assign(tag4.substr(separator + 1, tag4.length() - separator + 1));
-					tag4.erase(separator, tag4.length() - separator);
+					std::vector<std::string> devsearch = listowner->searchpath();
+					for (std::string &path : devsearch)
+						searchpath.emplace_back(std::move(path));
 				}
 
-				// prepare locations where we have to load from: list/parentname & list/clonename
-				std::string tag1(swlist.list_name());
-				tag1.append(PATH_SEPARATOR);
-				tag2.assign(tag1.append(tag4));
-				tag1.assign(swlist.list_name());
-				tag1.append(PATH_SEPARATOR);
-				tag3.assign(tag1.append(tag5));
-
-				if (tag5.find_first_of('%') != -1)
-					fatalerror("We do not support clones of clones!\n");
-
-				// try to load from the available location(s):
-				// - if we are not using lists, we have regiontag only;
-				// - if we are using lists, we have: list/clonename, list/parentname, clonename, parentname
-				// try to load from list/setname
-				if ((m_mame_file == nullptr) && (tag2.c_str() != nullptr))
-					m_mame_file = common_process_file(device().machine().options(), tag2.c_str(), has_crc, crc, romp, filerr);
-				// try to load from list/parentname
-				if ((m_mame_file == nullptr) && (tag3.c_str() != nullptr))
-					m_mame_file = common_process_file(device().machine().options(), tag3.c_str(), has_crc, crc, romp, filerr);
-				// try to load from setname
-				if ((m_mame_file == nullptr) && (tag4.c_str() != nullptr))
-					m_mame_file = common_process_file(device().machine().options(), tag4.c_str(), has_crc, crc, romp, filerr);
-				// try to load from parentname
-				if ((m_mame_file == nullptr) && (tag5.c_str() != nullptr))
-					m_mame_file = common_process_file(device().machine().options(), tag5.c_str(), has_crc, crc, romp, filerr);
-
-				warningcount += verify_length_and_hash(m_mame_file.get(),ROM_GETNAME(romp),ROM_GETLENGTH(romp), util::hash_collection(ROM_GETHASHDATA(romp)));
+				// try to load the file
+				m_mame_file.reset(new emu_file(device().machine().options().media_path(), searchpath, OPEN_FLAG_READ));
+				m_mame_file->set_restrict_to_mediapath(1);
+				osd_file::error filerr;
+				if (has_crc)
+					filerr = m_mame_file->open(ROM_GETNAME(romp), crc);
+				else
+					filerr = m_mame_file->open(ROM_GETNAME(romp));
+				if (filerr != osd_file::error::NONE)
+					m_mame_file.reset();
+
+				warningcount += verify_length_and_hash(m_mame_file.get(), ROM_GETNAME(romp), ROM_GETLENGTH(romp), util::hash_collection(ROM_GETHASHDATA(romp)));
 
 				if (filerr == osd_file::error::NONE)
 					filerr = util::core_file::open_proxy(*m_mame_file, m_file);
 				if (filerr == osd_file::error::NONE)
-					retVal = true;
+					retval = true;
 
 				break; // load first item for start
 			}
-			romp++; /* something else; skip */
 		}
 	}
+
 	if (warningcount > 0)
-	{
 		osd_printf_error("WARNING: the software item might not run correctly.\n");
-	}
-	return retVal;
+
+	return retval;
 }
 
 
diff --git a/src/emu/fileio.cpp b/src/emu/fileio.cpp
index 53eac8d55cf..5c392b01ffd 100644
--- a/src/emu/fileio.cpp
+++ b/src/emu/fileio.cpp
@@ -9,9 +9,31 @@
 ***************************************************************************/
 
 #include "emu.h"
-#include "unzip.h"
 #include "fileio.h"
 
+#include "unzip.h"
+
+//#define VERBOSE 1
+#define LOG_OUTPUT_FUNC osd_printf_verbose
+#include "logmacro.h"
+
+
+template path_iterator::path_iterator(char *&, int);
+template path_iterator::path_iterator(char * const &, int);
+template path_iterator::path_iterator(char const *&, int);
+template path_iterator::path_iterator(char const * const &, int);
+template path_iterator::path_iterator(std::vector<std::string> &, int);
+template path_iterator::path_iterator(const std::vector<std::string> &, int);
+
+template emu_file::emu_file(std::string &, u32);
+template emu_file::emu_file(const std::string &, u32);
+template emu_file::emu_file(char *&, u32);
+template emu_file::emu_file(char * const &, u32);
+template emu_file::emu_file(char const *&, u32);
+template emu_file::emu_file(char const * const &, u32);
+template emu_file::emu_file(std::vector<std::string> &, u32);
+template emu_file::emu_file(const std::vector<std::string> &, u32);
+
 
 const u32 OPEN_FLAG_HAS_CRC  = 0x10000;
 
@@ -28,6 +50,7 @@ const u32 OPEN_FLAG_HAS_CRC  = 0x10000;
 path_iterator::path_iterator(std::string &&searchpath)
 	: m_searchpath(std::move(searchpath))
 	, m_current(m_searchpath.cbegin())
+	, m_separator(';') // FIXME this should be a macro - UNIX prefers :
 	, m_is_first(true)
 {
 }
@@ -35,6 +58,7 @@ path_iterator::path_iterator(std::string &&searchpath)
 path_iterator::path_iterator(std::string const &searchpath)
 	: m_searchpath(searchpath)
 	, m_current(m_searchpath.cbegin())
+	, m_separator(';') // FIXME this should be a macro - UNIX prefers :
 	, m_is_first(true)
 {
 }
@@ -47,6 +71,7 @@ path_iterator::path_iterator(path_iterator &&that)
 path_iterator::path_iterator(path_iterator const &that)
 	: m_searchpath(that.m_searchpath)
 	, m_current(std::next(m_searchpath.cbegin(), std::distance(that.m_searchpath.cbegin(), that.m_current)))
+	, m_separator(that.m_separator)
 	, m_is_first(that.m_is_first)
 {
 }
@@ -61,6 +86,7 @@ path_iterator &path_iterator::operator=(path_iterator &&that)
 	auto const current(std::distance(that.m_searchpath.cbegin(), that.m_current));
 	m_searchpath = std::move(that.m_searchpath);
 	m_current = std::next(m_searchpath.cbegin(), current);
+	m_separator = that.m_separator;
 	m_is_first = that.m_is_first;
 	return *this;
 }
@@ -69,6 +95,7 @@ path_iterator &path_iterator::operator=(path_iterator const &that)
 {
 	m_searchpath = that.m_searchpath;
 	m_current = std::next(m_searchpath.cbegin(), std::distance(that.m_searchpath.cbegin(), that.m_current));
+	m_separator = that.m_separator;
 	m_is_first = that.m_is_first;
 	return *this;
 }
@@ -86,7 +113,7 @@ bool path_iterator::next(std::string &buffer, const char *name)
 		return false;
 
 	// copy up to the next separator
-	auto const sep(std::find(m_current, m_searchpath.cend(), ';')); // FIXME this should be a macro - UNIX prefers :
+	auto const sep(std::find(m_current, m_searchpath.cend(), m_separator));
 	buffer.assign(m_current, sep);
 	m_current = sep;
 	if (m_searchpath.cend() != m_current)
@@ -165,31 +192,31 @@ const osd::directory::entry *file_enumerator::next()
 //-------------------------------------------------
 
 emu_file::emu_file(u32 openflags)
-	: m_file()
-	, m_iterator(std::string())
-	, m_mediapaths(std::string())
-	, m_crc(0)
-	, m_openflags(openflags)
-	, m_zipfile(nullptr)
-	, m_ziplength(0)
-	, m_remove_on_close(false)
-	, m_restrict_to_mediapath(false)
+	: emu_file(path_iterator(std::string()), openflags)
 {
-	// sanity check the open flags
-	if ((m_openflags & OPEN_FLAG_HAS_CRC) && (m_openflags & OPEN_FLAG_WRITE))
-		throw emu_fatalerror("Attempted to open a file for write with OPEN_FLAG_HAS_CRC");
+
 }
 
-emu_file::emu_file(std::string &&searchpath, u32 openflags)
-	: m_file()
-	, m_iterator(searchpath)
-	, m_mediapaths(std::move(searchpath))
+emu_file::emu_file(path_iterator &&searchpath, u32 openflags)
+	: emu_file(openflags, EMPTY)
+{
+	m_iterator.emplace_back(searchpath, std::string());
+	m_mediapaths.emplace_back(std::move(searchpath), std::string());
+}
+
+emu_file::emu_file(u32 openflags, empty_t)
+	: m_filename()
+	, m_fullpath()
+	, m_file()
+	, m_iterator()
+	, m_mediapaths()
+	, m_first(true)
 	, m_crc(0)
 	, m_openflags(openflags)
 	, m_zipfile(nullptr)
 	, m_ziplength(0)
 	, m_remove_on_close(false)
-	, m_restrict_to_mediapath(false)
+	, m_restrict_to_mediapath(0)
 {
 	// sanity check the open flags
 	if ((m_openflags & OPEN_FLAG_HAS_CRC) && (m_openflags & OPEN_FLAG_WRITE))
@@ -279,7 +306,7 @@ osd_file::error emu_file::open(const std::string &name)
 	m_openflags &= ~OPEN_FLAG_HAS_CRC;
 
 	// reset the iterator and open_next
-	m_iterator.reset();
+	m_first = true;
 	return open_next();
 }
 
@@ -291,28 +318,10 @@ osd_file::error emu_file::open(const std::string &name, u32 crc)
 	m_openflags |= OPEN_FLAG_HAS_CRC;
 
 	// reset the iterator and open_next
-	m_iterator.reset();
+	m_first = true;
 	return open_next();
 }
 
-osd_file::error emu_file::open(const std::string &name1, const std::string &name2, u32 crc)
-{
-	// concatenate the strings and do a standard open
-	return open(name1 + name2, crc);
-}
-
-osd_file::error emu_file::open(const std::string &name1, const std::string &name2, const std::string &name3, u32 crc)
-{
-	// concatenate the strings and do a standard open
-	return open(name1 + name2 + name3, crc);
-}
-
-osd_file::error emu_file::open(const std::string &name1, const std::string &name2, const std::string &name3, const std::string &name4, u32 crc)
-{
-	// concatenate the strings and do a standard open
-	return open(name1 + name2 + name3 + name4, crc);
-}
-
 
 //-------------------------------------------------
 //  open_next - open the next file that matches
@@ -322,24 +331,64 @@ osd_file::error emu_file::open(const std::string &name1, const std::string &name
 osd_file::error emu_file::open_next()
 {
 	// if we're open from a previous attempt, close up now
-	if (m_file != nullptr)
+	if (m_file)
 		close();
 
 	// loop over paths
+	LOG("emu_file: open next '%s'\n", m_filename);
 	osd_file::error filerr = osd_file::error::NOT_FOUND;
-	while (m_iterator.next(m_fullpath, m_filename.c_str()))
+	while (osd_file::error::NONE != filerr)
 	{
+		if (m_first)
+		{
+			m_first = false;
+			for (searchpath_vector::value_type &i : m_iterator)
+			{
+				i.first.reset();
+				if (!i.first.next(i.second))
+					return filerr;
+			}
+		}
+		else
+		{
+			searchpath_vector::iterator i(m_iterator.begin());
+			while (i != m_iterator.end())
+			{
+				if (i->first.next(i->second))
+				{
+					LOG("emu_file: next path %d '%s'\n", std::distance(m_iterator.begin(), i), i->second);
+					for (searchpath_vector::iterator j = m_iterator.begin(); i != j; ++j)
+					{
+						j->first.reset();
+						j->first.next(j->second);
+					}
+					break;
+				}
+				++i;
+			}
+			if (m_iterator.end() == i)
+				return filerr;
+		}
+
+		// build full path
+		m_fullpath.clear();
+		for (searchpath_vector::value_type const &path : m_iterator)
+		{
+			m_fullpath.append(path.second);
+			if (!m_fullpath.empty() && !util::is_directory_separator(m_fullpath.back()))
+				m_fullpath.append(PATH_SEPARATOR);
+		}
+		m_fullpath.append(m_filename);
+
 		// attempt to open the file directly
+		LOG("emu_file: attempting to open '%s' directly\n", m_fullpath);
 		filerr = util::core_file::open(m_fullpath, m_openflags, m_file);
-		if (filerr == osd_file::error::NONE)
-			break;
 
 		// if we're opening for read-only we have other options
-		if ((m_openflags & (OPEN_FLAG_READ | OPEN_FLAG_WRITE)) == OPEN_FLAG_READ)
+		if ((osd_file::error::NONE != filerr) && ((m_openflags & (OPEN_FLAG_READ | OPEN_FLAG_WRITE)) == OPEN_FLAG_READ))
 		{
+			LOG("emu_file: attempting to open '%s' from archives\n", m_fullpath);
 			filerr = attempt_zipped();
-			if (filerr == osd_file::error::NONE)
-				break;
 		}
 	}
 	return filerr;
@@ -402,7 +451,7 @@ osd_file::error emu_file::compress(int level)
 //   loading if needed
 //-------------------------------------------------
 
-bool emu_file::compressed_file_ready(void)
+bool emu_file::compressed_file_ready()
 {
 	// load the ZIP file now if we haven't yet
 	if (m_zipfile && (load_zipped_file() != osd_file::error::NONE))
@@ -611,16 +660,55 @@ void emu_file::flush()
 //  any media path
 //-------------------------------------------------
 
-bool emu_file::part_of_mediapath(std::string path)
+bool emu_file::part_of_mediapath(const std::string &path)
 {
-	bool result = false;
+	if (!m_restrict_to_mediapath)
+		return true;
+
+	for (size_t i = 0U; (m_mediapaths.size() > i) && ((0 > m_restrict_to_mediapath) || (i < m_restrict_to_mediapath)); i++)
+	{
+		m_mediapaths[i].first.reset();
+		if (!m_mediapaths[i].first.next(m_mediapaths[i].second))
+			return false;
+	}
+
 	std::string mediapath;
-	m_mediapaths.reset();
-	while (m_mediapaths.next(mediapath, nullptr) && !result) {
-		if (path.compare(mediapath.substr(0, mediapath.length())))
-			result = true;
+	while (true)
+	{
+		mediapath.clear();
+		for (size_t i = 0U; (m_mediapaths.size() > i) && ((0 > m_restrict_to_mediapath) || (i < m_restrict_to_mediapath)); i++)
+		{
+			mediapath.append(m_mediapaths[i].second);
+			if (!mediapath.empty() && !util::is_directory_separator(mediapath.back()))
+				mediapath.append(PATH_SEPARATOR);
+		}
+
+		if (!path.compare(0, mediapath.size(), mediapath))
+		{
+			LOG("emu_file: path '%s' matches media path '%s'\n", path, mediapath);
+			return true;
+		}
+
+		size_t i = 0U;
+		while ((m_mediapaths.size() > i) && ((0 > m_restrict_to_mediapath) || (i < m_restrict_to_mediapath)))
+		{
+			if (m_mediapaths[i].first.next(m_mediapaths[i].second))
+			{
+				for (size_t j = 0U; i != j; j++)
+				{
+					m_mediapaths[j].first.reset();
+					m_mediapaths[j].first.next(m_mediapaths[j].second);
+				}
+				break;
+			}
+			i++;
+		}
+		if ((m_mediapaths.size() == i) || ((0 <= m_restrict_to_mediapath) && (i == m_restrict_to_mediapath)))
+		{
+			LOG("emu_file: path '%s' not in media path\n", path);
+			return false;
+		}
 	}
-	return result;
 }
 
 //-------------------------------------------------
@@ -641,21 +729,24 @@ osd_file::error emu_file::attempt_zipped()
 		// loop over directory parts up to the start of filename
 		while (1)
 		{
-			// find the final path separator
-			auto const dirsep = m_fullpath.find_last_of(PATH_SEPARATOR[0]);
-			if (dirsep == std::string::npos)
+			if (!part_of_mediapath(m_fullpath))
 				break;
 
-			if (restrict_to_mediapath() && !part_of_mediapath(m_fullpath))
+			// find the final path separator
+			auto const dirsepiter(std::find_if(m_fullpath.rbegin(), m_fullpath.rend(), util::is_directory_separator));
+			if (dirsepiter == m_fullpath.rend())
 				break;
+			std::string::size_type const dirsep(std::distance(m_fullpath.begin(), dirsepiter.base()) - 1);
 
 			// insert the part from the right of the separator into the head of the filename
-			if (!filename.empty()) filename.insert(0, 1, '/');
+			if (!filename.empty())
+				filename.insert(0, 1, '/');
 			filename.insert(0, m_fullpath.substr(dirsep + 1, std::string::npos));
 
 			// remove this part of the filename and append an archive extension
 			m_fullpath.resize(dirsep);
 			m_fullpath.append(suffixes[i]);
+			LOG("emu_file: looking for '%s' in archive '%s'\n", filename, m_fullpath);
 
 			// attempt to open the archive file
 			util::archive_file::ptr zip;
diff --git a/src/emu/fileio.h b/src/emu/fileio.h
index ad7ef5028a6..20be11eb022 100644
--- a/src/emu/fileio.h
+++ b/src/emu/fileio.h
@@ -16,6 +16,13 @@
 #include "corefile.h"
 #include "hash.h"
 
+#include <iterator>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+
 // some systems use macros for getc/putc rather than functions
 #ifdef getc
 #undef getc
@@ -37,6 +44,17 @@ public:
 	path_iterator(path_iterator &&that);
 	path_iterator(path_iterator const &that);
 
+	template <typename T>
+	path_iterator(T &&searchpath, std::enable_if_t<std::is_constructible<std::string, T>::value, int> = 0)
+		: path_iterator(std::string(std::forward<T>(searchpath)))
+	{ }
+
+	// TODO: this doesn't work with C arrays (only vector, std::array, etc.)
+	template <typename T>
+	path_iterator(T &&paths, std::enable_if_t<std::is_constructible<std::string, typename std::remove_reference_t<T>::value_type>::value, int> = 0)
+		: path_iterator(concatenate_paths(std::forward<T>(paths)))
+	{ m_separator = '\0'; }
+
 	// assignment operators
 	path_iterator &operator=(path_iterator &&that);
 	path_iterator &operator=(path_iterator const &that);
@@ -46,9 +64,30 @@ public:
 	void reset();
 
 private:
+	// helpers
+	template <typename T>
+	static std::string concatenate_paths(T &&paths)
+	{
+		std::string result;
+		auto it(std::begin(paths));
+		if (std::end(paths) != it)
+		{
+			result.append(*it);
+			++it;
+		}
+		while (std::end(paths) != it)
+		{
+			result.append(1, '\0');
+			result.append(*it);
+			++it;
+		}
+		return result;
+	}
+
 	// internal state
 	std::string                 m_searchpath;
 	std::string::const_iterator m_current;
+	char                        m_separator;
 	bool                        m_is_first;
 };
 
@@ -83,10 +122,24 @@ private:
 
 class emu_file
 {
+	enum empty_t { EMPTY };
+	using searchpath_vector = std::vector<std::pair<path_iterator, std::string> >;
+
 public:
 	// file open/creation
 	emu_file(u32 openflags);
-	emu_file(std::string &&searchpath, u32 openflags);
+	template <typename T>
+	emu_file(T &&searchpath, std::enable_if_t<std::is_constructible<path_iterator, T>::value, u32> openflags)
+		: emu_file(path_iterator(std::forward<T>(searchpath)), openflags)
+	{ }
+	template <typename T, typename U, typename V, typename... W>
+	emu_file(T &&searchpath, U &&x, V &&y, W &&... z)
+		: emu_file(0U, EMPTY)
+	{
+		m_iterator.reserve(sizeof...(W) + 1);
+		m_mediapaths.reserve(sizeof...(W) + 1);
+		set_searchpaths(std::forward<T>(searchpath), std::forward<U>(x), std::forward<V>(y), std::forward<W>(z)...);
+	}
 	virtual ~emu_file();
 
 	// getters
@@ -96,20 +149,15 @@ public:
 	const char *fullpath() const { return m_fullpath.c_str(); }
 	u32 openflags() const { return m_openflags; }
 	util::hash_collection &hashes(const char *types);
-	bool restrict_to_mediapath() const { return m_restrict_to_mediapath; }
-	bool part_of_mediapath(std::string path);
 
 	// setters
 	void remove_on_close() { m_remove_on_close = true; }
 	void set_openflags(u32 openflags) { assert(!m_file); m_openflags = openflags; }
-	void set_restrict_to_mediapath(bool rtmp = true) { m_restrict_to_mediapath = rtmp; }
+	void set_restrict_to_mediapath(int rtmp) { m_restrict_to_mediapath = rtmp; }
 
 	// open/close
 	osd_file::error open(const std::string &name);
 	osd_file::error open(const std::string &name, u32 crc);
-	osd_file::error open(const std::string &name1, const std::string &name2, u32 crc);
-	osd_file::error open(const std::string &name1, const std::string &name2, const std::string &name3, u32 crc);
-	osd_file::error open(const std::string &name1, const std::string &name2, const std::string &name3, const std::string &name4, u32 crc);
 	osd_file::error open_next();
 	osd_file::error open_ram(const void *data, u32 length);
 	void close();
@@ -142,7 +190,26 @@ public:
 	void flush();
 
 private:
-	bool compressed_file_ready(void);
+	emu_file(u32 openflags, empty_t);
+	emu_file(path_iterator &&searchpath, u32 openflags);
+
+	template <typename T>
+	void set_searchpaths(T &&searchpath, u32 openflags)
+	{
+		m_iterator.emplace_back(searchpath, "");
+		m_mediapaths.emplace_back(std::forward<T>(searchpath), "");
+		m_openflags = openflags;
+	}
+	template <typename T, typename U, typename V, typename... W>
+	void set_searchpaths(T &&searchpath, U &&x, V &&y, W &&... z)
+	{
+		m_iterator.emplace_back(searchpath, "");
+		m_mediapaths.emplace_back(std::forward<T>(searchpath), "");
+		set_searchpaths(std::forward<U>(x), std::forward<V>(y), std::forward<W>(z)...);
+	}
+
+	bool part_of_mediapath(const std::string &path);
+	bool compressed_file_ready();
 
 	// internal helpers
 	osd_file::error attempt_zipped();
@@ -152,18 +219,36 @@ private:
 	std::string             m_filename;             // original filename provided
 	std::string             m_fullpath;             // full filename
 	util::core_file::ptr    m_file;                 // core file pointer
-	path_iterator           m_iterator;             // iterator for paths
-	path_iterator           m_mediapaths;           // media-path iterator
+	searchpath_vector       m_iterator;             // iterator for paths
+	searchpath_vector       m_mediapaths;           // media-path iterator
+	bool                    m_first;                // true if this is the start of iteration
 	u32                     m_crc;                  // file's CRC
 	u32                     m_openflags;            // flags we used for the open
 	util::hash_collection   m_hashes;               // collection of hashes
 
 	std::unique_ptr<util::archive_file> m_zipfile;  // ZIP file pointer
-	std::vector<u8>         m_zipdata;               // ZIP file data
-	u64                     m_ziplength;             // ZIP file length
+	std::vector<u8>         m_zipdata;              // ZIP file data
+	u64                     m_ziplength;            // ZIP file length
 
-	bool                    m_remove_on_close;       // flag: remove the file when closing
-	bool                    m_restrict_to_mediapath; // flag: restrict to paths inside the media-path
+	bool                    m_remove_on_close;      // flag: remove the file when closing
+	int                     m_restrict_to_mediapath; // flag: restrict to paths inside the media-path
 };
 
+
+extern template path_iterator::path_iterator(char *&, int);
+extern template path_iterator::path_iterator(char * const &, int);
+extern template path_iterator::path_iterator(char const *&, int);
+extern template path_iterator::path_iterator(char const * const &, int);
+extern template path_iterator::path_iterator(std::vector<std::string> &, int);
+extern template path_iterator::path_iterator(const std::vector<std::string> &, int);
+
+extern template emu_file::emu_file(std::string &, u32);
+extern template emu_file::emu_file(const std::string &, u32);
+extern template emu_file::emu_file(char *&, u32);
+extern template emu_file::emu_file(char * const &, u32);
+extern template emu_file::emu_file(char const *&, u32);
+extern template emu_file::emu_file(char const * const &, u32);
+extern template emu_file::emu_file(std::vector<std::string> &, u32);
+extern template emu_file::emu_file(const std::vector<std::string> &, u32);
+
 #endif // MAME_EMU_FILEIO_H
diff --git a/src/emu/render.cpp b/src/emu/render.cpp
index f35ab90d431..8501bdf99df 100644
--- a/src/emu/render.cpp
+++ b/src/emu/render.cpp
@@ -1561,11 +1561,12 @@ void render_target::load_additional_layout_files(const char *basename, bool have
 	bool have_override = false;
 
 	// if override_artwork defined, load that and skip artwork other than default
-	if (m_manager.machine().options().override_artwork())
+	const char *const override_art = m_manager.machine().options().override_artwork();
+	if (override_art && *override_art)
 	{
-		if (load_layout_file(m_manager.machine().options().override_artwork(), m_manager.machine().options().override_artwork()))
+		if (load_layout_file(override_art, override_art))
 			have_override = true;
-		else if (load_layout_file(m_manager.machine().options().override_artwork(), "default"))
+		else if (load_layout_file(override_art, "default"))
 			have_override = true;
 	}
 
@@ -1582,7 +1583,7 @@ void render_target::load_additional_layout_files(const char *basename, bool have
 			have_artwork = true;
 
 		// if a default view has been specified, use that as a fallback
-		if (system.default_layout != nullptr)
+		if (system.default_layout)
 			have_default |= load_layout_file(nullptr, *system.default_layout);
 		m_manager.machine().config().apply_default_layouts(
 				[this, &have_default] (device_t &dev, internal_layout const &layout)
@@ -1590,36 +1591,30 @@ void render_target::load_additional_layout_files(const char *basename, bool have
 
 		// try to load another file based on the parent driver name
 		int cloneof = driver_list::clone(system);
-		if (cloneof != -1)
+		while (0 <= cloneof)
 		{
 			if (!load_layout_file(driver_list::driver(cloneof).name, driver_list::driver(cloneof).name))
 				have_artwork |= load_layout_file(driver_list::driver(cloneof).name, "default");
 			else
 				have_artwork = true;
+
+			// Check the parent of the parent to cover bios based artwork
+			const game_driver &parent(driver_list::driver(cloneof));
+			cloneof = driver_list::clone(parent);
 		}
 
-		// Check the parent of the parent to cover bios based artwork
-		if (cloneof != -1) {
-			const game_driver &clone(driver_list::driver(cloneof));
-			int cloneofclone = driver_list::clone(clone);
-			if (cloneofclone != -1 && cloneofclone != cloneof)
+		// Use fallback artwork if defined and no artwork has been found yet
+		if (!have_artwork)
+		{
+			const char *const fallback_art = m_manager.machine().options().fallback_artwork();
+			if (fallback_art && *fallback_art)
 			{
-				if (!load_layout_file(driver_list::driver(cloneofclone).name, driver_list::driver(cloneofclone).name))
-					have_artwork |= load_layout_file(driver_list::driver(cloneofclone).name, "default");
+				if (!load_layout_file(fallback_art, fallback_art))
+					have_artwork |= load_layout_file(fallback_art, "default");
 				else
 					have_artwork = true;
 			}
 		}
-
-		// Use fallback artwork if defined and no artwork has been found yet
-		if (!have_artwork && m_manager.machine().options().fallback_artwork())
-		{
-			if (!load_layout_file(m_manager.machine().options().fallback_artwork(), m_manager.machine().options().fallback_artwork()))
-				have_artwork |= load_layout_file(m_manager.machine().options().fallback_artwork(), "default");
-			else
-				have_artwork = true;
-		}
-
 	}
 
 	// local screen info to avoid repeated code
@@ -2041,6 +2036,7 @@ bool render_target::load_layout_file(const char *dirname, const char *filename)
 
 	// attempt to open the file; bail if we can't
 	emu_file layoutfile(m_manager.machine().options().art_path(), OPEN_FLAG_READ);
+	layoutfile.set_restrict_to_mediapath(1);
 	osd_file::error const filerr(layoutfile.open(fname));
 	if (filerr != osd_file::error::NONE)
 		return false;
diff --git a/src/emu/romload.cpp b/src/emu/romload.cpp
index 19f8d6296dc..4018cdf923e 100644
--- a/src/emu/romload.cpp
+++ b/src/emu/romload.cpp
@@ -15,6 +15,9 @@
 #include "softlist_dev.h"
 #include "ui/uimain.h"
 
+#include <algorithm>
+#include <set>
+
 
 #define LOG_LOAD 0
 #define LOG(...) do { if (LOG_LOAD) debugload(__VA_ARGS__); } while(0)
@@ -30,28 +33,108 @@
     HELPERS (also used by diimage.cpp)
  ***************************************************************************/
 
-static osd_file::error common_process_file(emu_options &options, const char *location, const char *ext, const rom_entry *romp, emu_file &image_file)
+namespace {
+
+rom_entry const *next_parent_system(game_driver const *&system, std::vector<rom_entry> &rom_entries)
 {
-	return (location && *location)
-			? image_file.open(util::string_format("%s" PATH_SEPARATOR "%s%s", location, ROM_GETNAME(romp), ext))
-			: image_file.open(std::string(ROM_GETNAME(romp)) + ext);
+	if (!system)
+		return nullptr;
+	int const parent(driver_list::find(system->parent));
+	if (0 > parent)
+	{
+		system = nullptr;
+		return nullptr;
+	}
+	else
+	{
+		system = &driver_list::driver(parent);
+		rom_entries = rom_build_entries(system->rom);
+		return &rom_entries[0];
+	}
 }
 
-std::unique_ptr<emu_file> common_process_file(emu_options &options, const char *location, bool has_crc, u32 crc, const rom_entry *romp, osd_file::error &filerr)
+
+chd_error do_open_disk(const emu_options &options, std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, const rom_entry *romp, chd_file &chd, std::function<const rom_entry * ()> next_parent)
 {
-	auto image_file = std::make_unique<emu_file>(options.media_path(), OPEN_FLAG_READ);
+	// hashes are fixed, but we might need to try multiple filenames
+	std::set<std::string> tried;
+	const util::hash_collection hashes(ROM_GETHASHDATA(romp));
+	std::string filename, fullpath;
+	const rom_entry *parent(nullptr);
+	chd_error result(CHDERR_FILE_NOT_FOUND);
+	while (romp && (CHDERR_NONE != result))
+	{
+		filename = ROM_GETNAME(romp);
+		filename.append(".chd");
+		if (tried.insert(filename).second)
+		{
+			// piggyback on emu_file to find the disk image file
+			std::unique_ptr<emu_file> imgfile;
+			for (const std::vector<std::string> &paths : searchpath)
+			{
+				imgfile.reset(new emu_file(options.media_path(), paths, OPEN_FLAG_READ));
+				imgfile->set_restrict_to_mediapath(1);
+				const osd_file::error filerr(imgfile->open(filename, OPEN_FLAG_READ));
+				if (osd_file::error::NONE == filerr)
+					break;
+				else
+					imgfile.reset();
+			}
 
-	if (has_crc)
-		filerr = image_file->open(location, PATH_SEPARATOR, ROM_GETNAME(romp), crc);
-	else
-		filerr = image_file->open(util::string_format("%s" PATH_SEPARATOR "%s", location, ROM_GETNAME(romp)));
+			// if we couldn't open a candidate file, report an error; otherwise reopen it as a CHD
+			if (imgfile)
+			{
+				fullpath = imgfile->fullpath();
+				imgfile.reset();
+				result = chd.open(fullpath.c_str());
+			}
+		}
 
-	if (filerr != osd_file::error::NONE)
-		image_file = nullptr;
+		// walk the parents looking for a CHD with the same hashes but a different name
+		if (CHDERR_NONE != result)
+		{
+			while (romp)
+			{
+				// find a file in a disk region
+				if (parent)
+					romp = rom_next_file(romp);
+				while (!parent || !romp)
+				{
+					if (!parent)
+					{
+						parent = next_parent();
+						if (!parent)
+						{
+							romp = nullptr;
+							break;
+						}
+						while (ROMENTRY_ISPARAMETER(parent) || ROMENTRY_ISSYSTEM_BIOS(parent) || ROMENTRY_ISDEFAULT_BIOS(parent))
+							++parent;
+						if (ROMENTRY_ISEND(parent))
+							parent = nullptr;
+					}
+					else
+					{
+						parent = rom_next_region(parent);
+					}
+					while (parent && !ROMREGION_ISDISKDATA(parent))
+						parent = rom_next_region(parent);
+					if (parent)
+						romp = rom_first_file(parent);
+				}
 
-	return image_file;
+				// try it if it matches the hashes
+				if (romp && (util::hash_collection(ROM_GETHASHDATA(romp)) == hashes))
+					break;
+			}
+		}
+	}
+	return result;
 }
 
+} // anonymous namespace
+
+
 /***************************************************************************
     ROM LOADING
 ***************************************************************************/
@@ -506,7 +589,7 @@ void rom_load_manager::region_post_process(memory_region *region, bool invert)
     up the parent and loading by checksum
 -------------------------------------------------*/
 
-std::unique_ptr<emu_file> rom_load_manager::open_rom_file(const char *regiontag, const rom_entry *romp, std::vector<std::string> &tried_file_names, bool from_list)
+std::unique_ptr<emu_file> rom_load_manager::open_rom_file(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, const rom_entry *romp, std::vector<std::string> &tried_file_names, bool from_list)
 {
 	osd_file::error filerr = osd_file::error::NOT_FOUND;
 	u32 const romsize = rom_file_size(romp);
@@ -520,93 +603,13 @@ std::unique_ptr<emu_file> rom_load_manager::open_rom_file(const char *regiontag,
 	bool const has_crc = util::hash_collection(ROM_GETHASHDATA(romp)).crc(crc);
 
 	// attempt reading up the chain through the parents
-	// It also automatically attempts any kind of load by checksum supported by the archives.
+	// it also automatically attempts any kind of load by checksum supported by the archives.
 	std::unique_ptr<emu_file> result;
-	for (int drv = driver_list::find(machine().system()); !result && (0 <= drv); drv = driver_list::clone(drv))
-	{
-		tried_file_names.emplace_back(driver_list::driver(drv).name);
-		result = common_process_file(machine().options(), driver_list::driver(drv).name, has_crc, crc, romp, filerr);
-	}
-
-	// if the region is load by name, load the ROM from there
-	if (!result && regiontag)
+	for (const std::vector<std::string> &paths : searchpath)
 	{
-		// check if we are dealing with softwarelists. if so, locationtag
-		// is actually a concatenation of: listname + setname + parentname
-		// separated by '%' (parentname being present only for clones)
-		std::string tag1(regiontag), tag2, tag3, tag4, tag5;
-		bool is_list = false;
-		bool has_parent = false;
-
-		int separator1 = tag1.find_first_of('%');
-		if (separator1 != -1)
-		{
-			is_list = true;
-
-			// we are loading through softlists, split the listname from the regiontag
-			tag4.assign(tag1.substr(separator1 + 1, tag1.length() - separator1 + 1));
-			tag1.erase(separator1, tag1.length() - separator1);
-			tag1.append(PATH_SEPARATOR);
-
-			// check if we are loading a clone (if this is the case also tag1 have a separator '%')
-			int separator2 = tag4.find_first_of('%');
-			if (separator2 != -1)
-			{
-				has_parent = true;
-
-				// we are loading a clone through softlists, split the setname from the parentname
-				tag5.assign(tag4.substr(separator2 + 1, tag4.length() - separator2 + 1));
-				tag4.erase(separator2, tag4.length() - separator2);
-			}
-
-			// prepare locations where we have to load from: list/parentname & list/clonename
-			std::string swlist(tag1);
-			tag2.assign(swlist.append(tag4));
-			if (has_parent)
-			{
-				swlist.assign(tag1);
-				tag3.assign(swlist.append(tag5));
-			}
-		}
-
-		if (tag5.find_first_of('%') != -1)
-			throw emu_fatalerror("We do not support clones of clones!\n");
-
-		// try to load from the available location(s):
-		// - if we are not using lists, we have regiontag only;
-		// - if we are using lists, we have: list/clonename, list/parentname, clonename, parentname
-		if (!is_list)
-		{
-			tried_file_names.emplace_back(tag1);
-			result = common_process_file(machine().options(), tag1.c_str(), has_crc, crc, romp, filerr);
-		}
-		else
-		{
-			// try to load from list/setname
-			if (!result && (tag2.c_str() != nullptr)) // FIXME: std::string::c_str will never return nullptr
-			{
-				tried_file_names.emplace_back(tag2);
-				result = common_process_file(machine().options(), tag2.c_str(), has_crc, crc, romp, filerr);
-			}
-			// try to load from list/parentname
-			if (!result && has_parent && (tag3.c_str() != nullptr)) // FIXME: std::string::c_str will never return nullptr
-			{
-				tried_file_names.emplace_back(tag3);
-				result = common_process_file(machine().options(), tag3.c_str(), has_crc, crc, romp, filerr);
-			}
-			// try to load from setname
-			if (!result && (tag4.c_str() != nullptr)) // FIXME: std::string::c_str will never return nullptr
-			{
-				tried_file_names.emplace_back(tag4);
-				result = common_process_file(machine().options(), tag4.c_str(), has_crc, crc, romp, filerr);
-			}
-			// try to load from parentname
-			if (!result && has_parent && (tag5.c_str() != nullptr)) // FIXME: std::string::c_str will never return nullptr
-			{
-				tried_file_names.emplace_back(tag5);
-				result = common_process_file(machine().options(), tag5.c_str(), has_crc, crc, romp, filerr);
-			}
-		}
+		result = open_rom_file(paths, tried_file_names, has_crc, crc, ROM_GETNAME(romp), filerr);
+		if (result)
+			break;
 	}
 
 	// update counters
@@ -621,6 +624,27 @@ std::unique_ptr<emu_file> rom_load_manager::open_rom_file(const char *regiontag,
 }
 
 
+std::unique_ptr<emu_file> rom_load_manager::open_rom_file(const std::vector<std::string> &paths, std::vector<std::string> &tried, bool has_crc, u32 crc, const std::string &name, osd_file::error &filerr)
+{
+	// record the set names we search
+	tried.insert(tried.end(), paths.begin(), paths.end());
+
+	// attempt to open the file
+	std::unique_ptr<emu_file> result(new emu_file(machine().options().media_path(), paths, OPEN_FLAG_READ));
+	result->set_restrict_to_mediapath(1);
+	if (has_crc)
+		filerr = result->open(name, crc);
+	else
+		filerr = result->open(name);
+
+	// don't return anything if unsuccessful
+	if (osd_file::error::NONE != filerr)
+		return nullptr;
+	else
+		return result;
+}
+
+
 /*-------------------------------------------------
     rom_fread - cheesy fread that fills with
     random data for a nullptr file
@@ -824,7 +848,7 @@ void rom_load_manager::copy_rom_data(const rom_entry *romp)
     for a region
 -------------------------------------------------*/
 
-void rom_load_manager::process_rom_entries(const device_t &device, const char *regiontag, const rom_entry *parent_region, const rom_entry *romp, bool from_list)
+void rom_load_manager::process_rom_entries(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, u8 bios, const rom_entry *parent_region, const rom_entry *romp, bool from_list)
 {
 	u32 lastflags = 0;
 	std::vector<std::string> tried_file_names;
@@ -845,7 +869,7 @@ void rom_load_manager::process_rom_entries(const device_t &device, const char *r
 
 		if (ROMENTRY_ISFILL(romp))
 		{
-			if (!ROM_GETBIOSFLAGS(romp) || ROM_GETBIOSFLAGS(romp) == device.system_bios())
+			if (!ROM_GETBIOSFLAGS(romp) || (ROM_GETBIOSFLAGS(romp) == bios))
 				fill_rom_data(romp);
 
 			romp++;
@@ -857,7 +881,7 @@ void rom_load_manager::process_rom_entries(const device_t &device, const char *r
 		else if (ROMENTRY_ISFILE(romp))
 		{
 			// handle files
-			bool const irrelevantbios = (ROM_GETBIOSFLAGS(romp) != 0) && (ROM_GETBIOSFLAGS(romp) != device.system_bios());
+			bool const irrelevantbios = (ROM_GETBIOSFLAGS(romp) != 0) && (ROM_GETBIOSFLAGS(romp) != bios);
 			rom_entry const *baserom = romp;
 			int explength = 0;
 
@@ -866,7 +890,7 @@ void rom_load_manager::process_rom_entries(const device_t &device, const char *r
 			std::unique_ptr<emu_file> file;
 			if (!irrelevantbios)
 			{
-				file = open_rom_file(regiontag, romp, tried_file_names, from_list);
+				file = open_rom_file(searchpath, romp, tried_file_names, from_list);
 				if (!file)
 					handle_missing_file(romp, tried_file_names, CHDERR_NONE);
 			}
@@ -926,186 +950,12 @@ void rom_load_manager::process_rom_entries(const device_t &device, const char *r
 
 
 /*-------------------------------------------------
-    open_disk_image - open a disk image,
-    searching up the parent and loading by
-    checksum
--------------------------------------------------*/
-
-int open_disk_image(emu_options &options, const game_driver *gamedrv, const rom_entry *romp, chd_file &image_chd, const char *locationtag)
-{
-	emu_file image_file(options.media_path(), OPEN_FLAG_READ);
-	const rom_entry *region, *rom;
-	osd_file::error filerr;
-	chd_error err;
-
-	/* attempt to open the properly named file, scanning up through parent directories */
-	filerr = osd_file::error::NOT_FOUND;
-	for (int searchdrv = driver_list::find(*gamedrv); searchdrv != -1 && filerr != osd_file::error::NONE; searchdrv = driver_list::clone(searchdrv))
-		filerr = common_process_file(options, driver_list::driver(searchdrv).name, ".chd", romp, image_file);
-
-	if (filerr != osd_file::error::NONE)
-		filerr = common_process_file(options, nullptr, ".chd", romp, image_file);
-
-	/* look for the disk in the locationtag too */
-	if (filerr != osd_file::error::NONE && locationtag != nullptr)
-	{
-		// check if we are dealing with softwarelists. if so, locationtag
-		// is actually a concatenation of: listname + setname + parentname
-		// separated by '%' (parentname being present only for clones)
-		std::string tag1(locationtag), tag2, tag3, tag4, tag5;
-		bool is_list = false;
-		bool has_parent = false;
-
-		int separator1 = tag1.find_first_of('%');
-		if (separator1 != -1)
-		{
-			is_list = true;
-
-			// we are loading through softlists, split the listname from the regiontag
-			tag4.assign(tag1.substr(separator1 + 1, tag1.length() - separator1 + 1));
-			tag1.erase(separator1, tag1.length() - separator1);
-			tag1.append(PATH_SEPARATOR);
-
-			// check if we are loading a clone (if this is the case also tag1 have a separator '%')
-			int separator2 = tag4.find_first_of('%');
-			if (separator2 != -1)
-			{
-				has_parent = true;
-
-				// we are loading a clone through softlists, split the setname from the parentname
-				tag5.assign(tag4.substr(separator2 + 1, tag4.length() - separator2 + 1));
-				tag4.erase(separator2, tag4.length() - separator2);
-			}
-
-			// prepare locations where we have to load from: list/parentname (if any) & list/clonename
-			std::string swlist(tag1);
-			tag2.assign(swlist.append(tag4));
-			if (has_parent)
-			{
-				swlist.assign(tag1);
-				tag3.assign(swlist.append(tag5));
-			}
-		}
-
-		if (tag5.find_first_of('%') != -1)
-			throw emu_fatalerror("We do not support clones of clones!\n");
-
-		// try to load from the available location(s):
-		// - if we are not using lists, we have locationtag only;
-		// - if we are using lists, we have: list/clonename, list/parentname, clonename, parentname
-		if (!is_list)
-			filerr = common_process_file(options, locationtag, ".chd", romp, image_file);
-		else
-		{
-			// try to load from list/setname
-			if ((filerr != osd_file::error::NONE) && (tag2.c_str() != nullptr))
-				filerr = common_process_file(options, tag2.c_str(), ".chd", romp, image_file);
-			// try to load from list/parentname (if any)
-			if ((filerr != osd_file::error::NONE) && has_parent && (tag3.c_str() != nullptr))
-				filerr = common_process_file(options, tag3.c_str(), ".chd", romp, image_file);
-			// try to load from setname
-			if ((filerr != osd_file::error::NONE) && (tag4.c_str() != nullptr))
-				filerr = common_process_file(options, tag4.c_str(), ".chd", romp, image_file);
-			// try to load from parentname (if any)
-			if ((filerr != osd_file::error::NONE) && has_parent && (tag5.c_str() != nullptr))
-				filerr = common_process_file(options, tag5.c_str(), ".chd", romp, image_file);
-			// only for CHD we also try to load from list/
-			if ((filerr != osd_file::error::NONE) && (tag1.c_str() != nullptr))
-			{
-				tag1.erase(tag1.length() - 1, 1);    // remove the PATH_SEPARATOR
-				filerr = common_process_file(options, tag1.c_str(), ".chd", romp, image_file);
-			}
-		}
-	}
-
-	/* did the file open succeed? */
-	if (filerr == osd_file::error::NONE)
-	{
-		std::string fullpath(image_file.fullpath());
-		image_file.close();
-
-		/* try to open the CHD */
-		err = image_chd.open(fullpath.c_str());
-		if (err == CHDERR_NONE)
-			return err;
-	}
-	else
-		err = CHDERR_FILE_NOT_FOUND;
-
-	// Otherwise, look at our parents for a CHD with an identical checksum
-	// and try to open that
-	//
-	// An example of a system that requires this is src/mame/drivers/ksys673.cpp, that has declarations like this:
-	//      ...
-	//      DISK_IMAGE_READONLY("889aa", 0, BAD_DUMP SHA1(0b567bf2f03ee8089e0b021ea502a53b3f6fe7ac))
-	//      ...
-	//      DISK_IMAGE_READONLY("889ea", 0, BAD_DUMP SHA1(0b567bf2f03ee8089e0b021ea502a53b3f6fe7ac))
-	//      ...
-	//      DISK_IMAGE_READONLY("889ja", 0, BAD_DUMP SHA1(0b567bf2f03ee8089e0b021ea502a53b3f6fe7ac))
-	//      ...
-	//      DISK_IMAGE_READONLY("889ua", 0, BAD_DUMP SHA1(0b567bf2f03ee8089e0b021ea502a53b3f6fe7ac))
-	//      ...
-	util::hash_collection romphashes(ROM_GETHASHDATA(romp));
-	for (int drv = driver_list::find(*gamedrv); drv != -1; drv = driver_list::clone(drv))
-	{
-		const game_driver &current_driver(driver_list::driver(drv));
-
-		// Create a single use emu_option structure for the purposes of this lookup, just
-		// carrying forward the options that are necessary for CHD lookup.  This is because the
-		// options passed to us may have slot/image configurations that are "poisonous" for these
-		// other drivers
-		//
-		// A side effect of this approach is that the "dragnet" to find CHDs with identical hashes
-		// will only find CHDs for the default configuration.  I believe that this in practice will
-		// be acceptable.
-		emu_options driver_specific_options;
-		driver_specific_options.set_system_name(current_driver.name);
-		driver_specific_options.set_value(OPTION_MEDIAPATH, options.media_path(), OPTION_PRIORITY_DEFAULT);
-		driver_specific_options.set_value(OPTION_DIFF_DIRECTORY, options.diff_directory(), OPTION_PRIORITY_DEFAULT);
-
-		// Now that we have an emu_options structure properly set up, we can create a machine_config
-		machine_config config(current_driver, driver_specific_options);
-
-		for (device_t &device : device_iterator(config.root_device()))
-			for (region = rom_first_region(device); region != nullptr; region = rom_next_region(region))
-				if (ROMREGION_ISDISKDATA(region))
-					for (rom = rom_first_file(region); rom != nullptr; rom = rom_next_file(rom))
-
-						// Look for a differing name but with the same hash data
-						if (strcmp(ROM_GETNAME(romp), ROM_GETNAME(rom)) != 0 &&
-							romphashes == util::hash_collection(ROM_GETHASHDATA(rom)))
-						{
-							// Attempt to open the properly named file, scanning up through parent directories
-							filerr = osd_file::error::NOT_FOUND;
-							for (int searchdrv = drv; searchdrv != -1 && filerr != osd_file::error::NONE; searchdrv = driver_list::clone(searchdrv))
-								filerr = common_process_file(driver_specific_options, driver_list::driver(searchdrv).name, ".chd", rom, image_file);
-
-							if (filerr != osd_file::error::NONE)
-								filerr = common_process_file(driver_specific_options, nullptr, ".chd", rom, image_file);
-
-							// Did the file open succeed?
-							if (filerr == osd_file::error::NONE)
-							{
-								std::string fullpath(image_file.fullpath());
-								image_file.close();
-
-								// try to open the CHD
-								err = image_chd.open(fullpath.c_str());
-								if (err == CHDERR_NONE)
-									return err;
-							}
-						}
-	}
-	return err;
-}
-
-
-/*-------------------------------------------------
     open_disk_diff - open a DISK diff file
 -------------------------------------------------*/
 
 chd_error rom_load_manager::open_disk_diff(emu_options &options, const rom_entry *romp, chd_file &source, chd_file &diff_chd)
 {
+	// TODO: use system name and/or software list name in the path - the current setup doesn't scale
 	std::string fname = std::string(ROM_GETNAME(romp)).append(".dif");
 
 	/* try to open the diff */
@@ -1149,11 +999,11 @@ chd_error rom_load_manager::open_disk_diff(emu_options &options, const rom_entry
     for a region
 -------------------------------------------------*/
 
-void rom_load_manager::process_disk_entries(const char *regiontag, const rom_entry *parent_region, const rom_entry *romp, const char *locationtag)
+void rom_load_manager::process_disk_entries(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, const char *regiontag, const rom_entry *romp, std::function<const rom_entry * ()> next_parent)
 {
 	/* remove existing disk entries for this region */
 	m_chd_list.erase(std::remove_if(m_chd_list.begin(), m_chd_list.end(),
-		[regiontag](std::unique_ptr<open_chd> &chd){ return !strcmp(chd->region(), regiontag); }), m_chd_list.end());
+			[regiontag] (std::unique_ptr<open_chd> &chd) { return !strcmp(chd->region(), regiontag); }), m_chd_list.end());
 
 	/* loop until we hit the end of this region */
 	for ( ; !ROMENTRY_ISREGIONEND(romp); romp++)
@@ -1162,16 +1012,15 @@ void rom_load_manager::process_disk_entries(const char *regiontag, const rom_ent
 		if (ROMENTRY_ISFILE(romp))
 		{
 			auto chd = std::make_unique<open_chd>(regiontag);
-
-			util::hash_collection hashes(ROM_GETHASHDATA(romp));
 			chd_error err;
 
 			/* make the filename of the source */
-			std::string filename = std::string(ROM_GETNAME(romp)).append(".chd");
+			const std::string filename = std::string(ROM_GETNAME(romp)).append(".chd");
 
 			/* first open the source drive */
+			// FIXME: we've lost the ability to search parents here
 			LOG("Opening disk image: %s\n", filename.c_str());
-			err = chd_error(open_disk_image(machine().options(), &machine().system(), romp, chd->orig_chd(), locationtag));
+			err = do_open_disk(machine().options(), searchpath, romp, chd->orig_chd(), next_parent);
 			if (err != CHDERR_NONE)
 			{
 				handle_missing_file(romp, std::vector<std::string>(), err);
@@ -1184,6 +1033,7 @@ void rom_load_manager::process_disk_entries(const char *regiontag, const rom_ent
 			acthashes.add_sha1(chd->orig_chd().sha1());
 
 			/* verify the hash */
+			const util::hash_collection hashes(ROM_GETHASHDATA(romp));
 			if (hashes != acthashes)
 			{
 				m_errorstring.append(string_format("%s WRONG CHECKSUMS:\n", filename));
@@ -1218,6 +1068,57 @@ void rom_load_manager::process_disk_entries(const char *regiontag, const rom_ent
 }
 
 
+chd_error rom_load_manager::open_disk_image(const emu_options &options, const device_t &device, const rom_entry *romp, chd_file &image_chd)
+{
+	const std::vector<std::string> searchpath(device.searchpath());
+
+	driver_device const *const driver(dynamic_cast<driver_device const *>(&device));
+	std::function<const rom_entry * ()> next_parent;
+	if (driver)
+		next_parent = [sys = &driver->system(), roms = std::vector<rom_entry>()] () mutable { return next_parent_system(sys, roms); };
+	else
+		next_parent = [] () { return nullptr; };
+	return do_open_disk(options, { searchpath }, romp, image_chd, std::move(next_parent));
+}
+
+
+chd_error rom_load_manager::open_disk_image(const emu_options &options, software_list_device &swlist, const software_info &swinfo, const rom_entry *romp, chd_file &image_chd)
+{
+	std::vector<software_info const *> parents;
+	std::vector<std::string> listsearch, freesearch, disksearch;
+	disksearch.emplace_back(swlist.list_name());
+
+	for (software_info const *i = &swinfo; i; )
+	{
+		if (std::find(parents.begin(), parents.end(), i) != parents.end())
+			break;
+		parents.emplace_back(i);
+		listsearch.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), i->shortname()));
+		freesearch.emplace_back(i->shortname());
+		i = i->parentname().empty() ? nullptr : swlist.find(i->parentname());
+	}
+
+	auto part(parents.front()->parts().end());
+	return do_open_disk(
+			options,
+			{ listsearch, freesearch, disksearch },
+			romp,
+			image_chd,
+			[&parents, current = parents.cbegin(), part, end = part] () mutable -> const rom_entry *
+			{
+				if (part == end)
+				{
+					if (parents.end() == current)
+						return nullptr;
+					part = (*current)->parts().cbegin();
+					end = (*current)->parts().cend();
+					do { ++current; } while ((parents.cend() != current) && (*current)->parts().empty());
+				}
+				return &(*part++).romdata()[0];
+			});
+}
+
+
 /*-------------------------------------------------
     normalize_flags_for_device - modify the region
     flags for the given device
@@ -1266,9 +1167,6 @@ void rom_load_manager::normalize_flags_for_device(const char *rgntag, u8 &width,
 
 void rom_load_manager::load_software_part_region(device_t &device, software_list_device &swlist, const char *swname, const rom_entry *start_region)
 {
-	std::string locationtag(swlist.list_name()), breakstr("%");
-	const rom_entry *region;
-
 	m_errorstring.clear();
 	m_softwarningstring.clear();
 
@@ -1276,10 +1174,16 @@ void rom_load_manager::load_software_part_region(device_t &device, software_list
 	m_romstotalsize = 0;
 	m_romsloadedsize = 0;
 
+	std::vector<const software_info *> parents;
+	std::vector<std::string> listsearch, freesearch, disksearch, devsearch;
+	listsearch.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), swname));
+	freesearch.emplace_back(swname);
 	const software_info *swinfo = swlist.find(swname);
-	if (swinfo != nullptr)
+	if (swinfo)
 	{
-		u32 supported = swinfo->supported();
+		// dispay a warning for unsupported software
+		// TODO: list supported clones like we do for machines?
+		const u32 supported(swinfo->supported());
 		if (supported == SOFTWARE_SUPPORTED_PARTIAL)
 		{
 			m_errorstring.append(string_format("WARNING: support for software %s (in list %s) is only partial\n", swname, swlist.list_name()));
@@ -1291,34 +1195,45 @@ void rom_load_manager::load_software_part_region(device_t &device, software_list
 			m_softwarningstring.append(string_format("Support for software %s (in list %s) is only preliminary\n", swname, swlist.list_name()));
 		}
 
-		// attempt reading up the chain through the parents and create a locationtag std::string in the format
-		// " swlist % clonename % parentname "
-		// open_rom_file contains the code to split the elements and to create paths to load from
-
-		locationtag.append(breakstr);
-
-		while (swinfo != nullptr)
+		// walk the chain of parents and add them to the search path
+		parents.emplace_back(swinfo);
+		swinfo = !swinfo->parentname().empty() ? swlist.find(swinfo->parentname()) : nullptr;
+		while (swinfo)
 		{
-			locationtag.append(swinfo->shortname()).append(breakstr);
+			if (std::find(parents.begin(), parents.end(), swinfo) != parents.end())
+			{
+				m_errorstring.append(util::string_format("WARNING: parent/clone relationships form a loop for software %s (in list %s)\n", swname, swlist.list_name()));
+				m_softwarningstring.append(util::string_format("Parent/clone relationships from a loop for software %s (in list %s)\n", swname, swlist.list_name()));
+				break;
+			}
+			parents.emplace_back(swinfo);
+			listsearch.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), swinfo->shortname()));
+			freesearch.emplace_back(swinfo->shortname());
 			swinfo = !swinfo->parentname().empty() ? swlist.find(swinfo->parentname()) : nullptr;
 		}
-		// strip the final '%'
-		locationtag.erase(locationtag.length() - 1, 1);
 	}
 
+	// this is convenient for CD-only lists so you don't need an extra level of directories containing one file each
+	disksearch.emplace_back(swlist.list_name());
 
-	/* loop until we hit the end */
-	for (region = start_region; region != nullptr; region = rom_next_region(region))
+	// for historical reasons, add the search path for the software list device's owner
+	const device_t *const listowner = swlist.owner();
+	if (listowner)
+		devsearch = listowner->searchpath();
+
+	// loop until we hit the end
+	std::function<const rom_entry * ()> next_parent;
+	for (const rom_entry *region = start_region; region != nullptr; region = rom_next_region(region))
 	{
 		u32 regionlength = ROMREGION_GETLENGTH(region);
 
 		std::string regiontag = device.subtag(ROMREGION_GETTAG(region));
 		LOG("Processing region \"%s\" (length=%X)\n", regiontag.c_str(), regionlength);
 
-		/* the first entry must be a region */
+		// the first entry must be a region
 		assert(ROMENTRY_ISREGION(region));
 
-		/* if this is a device region, override with the device width and endianness */
+		// if this is a device region, override with the device width and endianness
 		endianness_t endianness = ROMREGION_ISBIGENDIAN(region) ? ENDIANNESS_BIG : ENDIANNESS_LITTLE;
 		u8 width = ROMREGION_GETWIDTH(region) / 8;
 		memory_region *memregion = machine().root_device().memregion(regiontag);
@@ -1326,47 +1241,76 @@ void rom_load_manager::load_software_part_region(device_t &device, software_list
 		{
 			normalize_flags_for_device(regiontag.c_str(), width, endianness);
 
-			/* clear old region (todo: should be moved to an image unload function) */
+			// clear old region (TODO: should be moved to an image unload function)
 			machine().memory().region_free(memregion->name());
 		}
 
-		/* remember the base and length */
+		// remember the base and length
 		m_region = machine().memory().region_alloc(regiontag.c_str(), regionlength, width, endianness);
 		LOG("Allocated %X bytes @ %p\n", m_region->bytes(), m_region->base());
 
-		/* clear the region if it's requested */
-		if (ROMREGION_ISERASE(region))
+		if (ROMREGION_ISERASE(region)) // clear the region if it's requested
 			memset(m_region->base(), ROMREGION_GETERASEVAL(region), m_region->bytes());
-
-		/* or if it's sufficiently small (<= 4MB) */
-		else if (m_region->bytes() <= 0x400000)
+		else if (m_region->bytes() <= 0x400000) // or if it's sufficiently small (<= 4MB)
 			memset(m_region->base(), 0, m_region->bytes());
-
 #ifdef MAME_DEBUG
-		/* if we're debugging, fill region with random data to catch errors */
-		else
+		else // if we're debugging, fill region with random data to catch errors
 			fill_random(m_region->base(), m_region->bytes());
 #endif
 
-		/* update total number of roms */
+		// update total number of roms
 		for (const rom_entry *rom = rom_first_file(region); rom != nullptr; rom = rom_next_file(rom))
 		{
 			m_romstotal++;
 			m_romstotalsize += rom_file_size(rom);
 		}
 
-		/* now process the entries in the region */
+		// now process the entries in the region
 		if (ROMREGION_ISROMDATA(region))
-			process_rom_entries(device, locationtag.c_str(), region, region + 1, true);
+		{
+			if (devsearch.empty())
+				process_rom_entries({ listsearch, freesearch }, 0U, region, region + 1, true);
+			else
+				process_rom_entries({ listsearch, freesearch, devsearch }, 0U, region, region + 1, true);
+		}
 		else if (ROMREGION_ISDISKDATA(region))
-			process_disk_entries(regiontag.c_str(), region, region + 1, locationtag.c_str());
+		{
+			if (!next_parent)
+			{
+				if (!parents.empty())
+				{
+					auto part(parents.front()->parts().end());
+					next_parent =
+							[&parents, current = parents.cbegin(), part, end = part] () mutable -> const rom_entry *
+							{
+								if (part == end)
+								{
+									if (parents.end() == current)
+										return nullptr;
+									part = (*current)->parts().cbegin();
+									end = (*current)->parts().cend();
+									do { ++current; } while ((parents.cend() != current) && (*current)->parts().empty());
+								}
+								return &(*part++).romdata()[0];
+							};
+				}
+				else
+				{
+					next_parent = [] () { return nullptr; };
+				}
+			}
+			if (devsearch.empty())
+				process_disk_entries({ listsearch, freesearch, disksearch }, regiontag.c_str(), region + 1, next_parent);
+			else
+				process_disk_entries({ listsearch, freesearch, disksearch, devsearch }, regiontag.c_str(), region + 1, next_parent);
+		}
 	}
 
-	/* now go back and post-process all the regions */
-	for (region = start_region; region != nullptr; region = rom_next_region(region))
+	// now go back and post-process all the regions
+	for (const rom_entry *region = start_region; region != nullptr; region = rom_next_region(region))
 		region_post_process(device.memregion(ROMREGION_GETTAG(region)), ROMREGION_ISINVERTED(region));
 
-	/* display the results and exit */
+	// display the results and exit
 	display_rom_load_results(true);
 }
 
@@ -1377,10 +1321,13 @@ void rom_load_manager::load_software_part_region(device_t &device, software_list
 
 void rom_load_manager::process_region_list()
 {
-	/* loop until we hit the end */
+	// loop until we hit the end
 	device_iterator deviter(machine().root_device());
+	std::vector<std::string> searchpath;
 	for (device_t &device : deviter)
 	{
+		searchpath.clear();
+		std::function<const rom_entry * ()> next_parent;
 		for (const rom_entry *region = rom_first_region(device); region != nullptr; region = rom_next_region(region))
 		{
 			u32 regionlength = ROMREGION_GETLENGTH(region);
@@ -1388,17 +1335,17 @@ void rom_load_manager::process_region_list()
 			std::string regiontag = device.subtag(ROM_GETNAME(region));
 			LOG("Processing region \"%s\" (length=%X)\n", regiontag.c_str(), regionlength);
 
-			/* the first entry must be a region */
+			// the first entry must be a region
 			assert(ROMENTRY_ISREGION(region));
 
 			if (ROMREGION_ISROMDATA(region))
 			{
-				/* if this is a device region, override with the device width and endianness */
+				// if this is a device region, override with the device width and endianness
 				u8 width = ROMREGION_GETWIDTH(region) / 8;
 				endianness_t endianness = ROMREGION_ISBIGENDIAN(region) ? ENDIANNESS_BIG : ENDIANNESS_LITTLE;
 				normalize_flags_for_device(regiontag.c_str(), width, endianness);
 
-				/* remember the base and length */
+				// remember the base and length
 				m_region = machine().memory().region_alloc(regiontag.c_str(), regionlength, width, endianness);
 				LOG("Allocated %X bytes @ %p\n", m_region->bytes(), m_region->base());
 
@@ -1412,11 +1359,25 @@ void rom_load_manager::process_region_list()
 #endif
 
 				// now process the entries in the region
-				process_rom_entries(device, device.shortname(), region, region + 1, false);
+				if (searchpath.empty())
+					searchpath = device.searchpath();
+				assert(!searchpath.empty());
+				process_rom_entries({ searchpath }, device.system_bios(), region, region + 1, false);
 			}
 			else if (ROMREGION_ISDISKDATA(region))
 			{
-				process_disk_entries(regiontag.c_str(), region, region + 1, nullptr);
+				if (searchpath.empty())
+					searchpath = device.searchpath();
+				assert(!searchpath.empty());
+				if (!next_parent)
+				{
+					driver_device const *const driver(dynamic_cast<driver_device const *>(&device));
+					if (driver)
+						next_parent = [sys = &driver->system(), roms = std::vector<rom_entry>()] () mutable { return next_parent_system(sys, roms); };
+					else
+						next_parent = [] () { return nullptr; };
+				}
+				process_disk_entries({ searchpath }, regiontag.c_str(), region + 1, next_parent);
 			}
 		}
 	}
diff --git a/src/emu/romload.h b/src/emu/romload.h
index 87f3054326d..7db106a52ce 100644
--- a/src/emu/romload.h
+++ b/src/emu/romload.h
@@ -6,15 +6,18 @@
 
     ROM loading functions.
 *********************************************************************/
-
-#pragma once
-
 #ifndef MAME_EMU_ROMLOAD_H
 #define MAME_EMU_ROMLOAD_H
 
+#pragma once
+
 #include "chd.h"
 
+#include <functional>
+#include <initializer_list>
+#include <string>
 #include <type_traits>
+#include <vector>
 
 
 /***************************************************************************
@@ -420,6 +423,10 @@ public:
 
 	void load_software_part_region(device_t &device, software_list_device &swlist, const char *swname, const rom_entry *start_region);
 
+	/* open a disk image, searching up the parent and loading by checksum */
+	static chd_error open_disk_image(const emu_options &options, const device_t &device, const rom_entry *romp, chd_file &image_chd);
+	static chd_error open_disk_image(const emu_options &options, software_list_device &swlist, const software_info &swinfo, const rom_entry *romp, chd_file &image_chd);
+
 private:
 	void determine_bios_rom(device_t &device, const char *specbios);
 	void count_roms();
@@ -430,18 +437,18 @@ private:
 	void display_loading_rom_message(const char *name, bool from_list);
 	void display_rom_load_results(bool from_list);
 	void region_post_process(memory_region *region, bool invert);
-	std::unique_ptr<emu_file> open_rom_file(const char *regiontag, const rom_entry *romp, std::vector<std::string> &tried_file_names, bool from_list);
+	std::unique_ptr<emu_file> open_rom_file(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, const rom_entry *romp, std::vector<std::string> &tried_file_names, bool from_list);
+	std::unique_ptr<emu_file> open_rom_file(const std::vector<std::string> &paths, std::vector<std::string> &tried, bool has_crc, u32 crc, const std::string &name, osd_file::error &filerr);
 	int rom_fread(emu_file *file, u8 *buffer, int length, const rom_entry *parent_region);
 	int read_rom_data(emu_file *file, const rom_entry *parent_region, const rom_entry *romp);
 	void fill_rom_data(const rom_entry *romp);
 	void copy_rom_data(const rom_entry *romp);
-	void process_rom_entries(const device_t &device, const char *regiontag, const rom_entry *parent_region, const rom_entry *romp, bool from_list);
+	void process_rom_entries(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, u8 bios, const rom_entry *parent_region, const rom_entry *romp, bool from_list);
 	chd_error open_disk_diff(emu_options &options, const rom_entry *romp, chd_file &source, chd_file &diff_chd);
-	void process_disk_entries(const char *regiontag, const rom_entry *parent_region, const rom_entry *romp, const char *locationtag);
+	void process_disk_entries(std::initializer_list<std::reference_wrapper<const std::vector<std::string> > > searchpath, const char *regiontag, const rom_entry *romp, std::function<const rom_entry * ()> next_parent);
 	void normalize_flags_for_device(const char *rgntag, u8 &width, endianness_t &endian);
 	void process_region_list();
 
-
 	// internal state
 	running_machine &   m_machine;            // reference to our machine
 
@@ -465,8 +472,6 @@ private:
 
 /* ----- Helpers ----- */
 
-std::unique_ptr<emu_file> common_process_file(emu_options &options, const char *location, bool has_crc, u32 crc, const rom_entry *romp, osd_file::error &filerr);
-
 /* return pointer to the first ROM region within a source */
 const rom_entry *rom_first_region(const device_t &device);
 
@@ -491,8 +496,4 @@ const rom_entry *rom_next_parameter(const rom_entry *romp);
 // builds a rom_entry vector from a tiny_rom_entry array
 std::vector<rom_entry> rom_build_entries(const tiny_rom_entry *tinyentries);
 
-
-/* open a disk image, searching up the parent and loading by checksum */
-int open_disk_image(emu_options &options, const game_driver *gamedrv, const rom_entry *romp, chd_file &image_chd, const char *locationtag);
-
 #endif  // MAME_EMU_ROMLOAD_H
diff --git a/src/emu/softlist_dev.cpp b/src/emu/softlist_dev.cpp
index 9d5e03d9b3a..d33e357ebc7 100644
--- a/src/emu/softlist_dev.cpp
+++ b/src/emu/softlist_dev.cpp
@@ -9,10 +9,11 @@
 ***************************************************************************/
 
 #include "emu.h"
-#include "emuopts.h"
+#include "softlist_dev.h"
+
 #include "diimage.h"
+#include "emuopts.h"
 #include "romload.h"
-#include "softlist_dev.h"
 #include "validity.h"
 
 #include <cctype>
diff --git a/src/frontend/mame/audit.cpp b/src/frontend/mame/audit.cpp
index 256f9876f1b..3ff706d2c8a 100644
--- a/src/frontend/mame/audit.cpp
+++ b/src/frontend/mame/audit.cpp
@@ -9,14 +9,19 @@
 ***************************************************************************/
 
 #include "emu.h"
-#include "emuopts.h"
 #include "audit.h"
-#include "chd.h"
+
+#include "sound/samples.h"
+
+#include "emuopts.h"
 #include "drivenum.h"
 #include "romload.h"
-#include "sound/samples.h"
 #include "softlist_dev.h"
 
+#include "chd.h"
+
+#include <algorithm>
+
 
 //**************************************************************************
 //  CORE FUNCTIONS
@@ -29,7 +34,6 @@
 media_auditor::media_auditor(const driver_enumerator &enumerator)
 	: m_enumerator(enumerator)
 	, m_validation(AUDIT_VALIDATE_FULL)
-	, m_searchpath()
 {
 }
 
@@ -53,22 +57,19 @@ media_auditor::summary media_auditor::audit_media(const char *validation)
 	std::size_t shared_required = 0;
 
 	// iterate over devices and regions
+	std::vector<std::string> searchpath;
 	for (device_t &device : device_iterator(m_enumerator.config()->root_device()))
 	{
-		// determine the search path for this source and iterate through the regions
-		m_searchpath.clear();
-		for (const std::string &path : device.searchpath())
-		{
-			if (!m_searchpath.empty())
-				m_searchpath += ';';
-			m_searchpath += path;
-		}
+		searchpath.clear();
 
 		// now iterate over regions and ROMs within
 		for (const rom_entry *region = rom_first_region(device); region; region = rom_next_region(region))
 		{
 			for (const rom_entry *rom = rom_first_file(region); rom; rom = rom_next_file(rom))
 			{
+				if (searchpath.empty())
+					searchpath = device.searchpath();
+
 				char const *const name(ROM_GETNAME(rom));
 				util::hash_collection const hashes(ROM_GETHASHDATA(rom));
 				device_t *const shared_device(find_shared_device(device, name, hashes, ROM_GETLENGTH(rom)));
@@ -83,9 +84,9 @@ media_auditor::summary media_auditor::audit_media(const char *validation)
 
 				audit_record *record = nullptr;
 				if (ROMREGION_ISROMDATA(region))
-					record = &audit_one_rom(rom);
+					record = &audit_one_rom(searchpath, rom);
 				else if (ROMREGION_ISDISKDATA(region))
-					record = &audit_one_disk(rom, nullptr);
+					record = &audit_one_disk(rom, device);
 
 				if (record)
 				{
@@ -126,12 +127,32 @@ media_auditor::summary media_auditor::audit_device(device_t &device, const char
 
 	// store validation for later
 	m_validation = validation;
-	m_searchpath = device.shortname();
 
 	std::size_t found = 0;
 	std::size_t required = 0;
 
-	audit_regions(rom_first_region(device), nullptr, found, required);
+	std::vector<std::string> searchpath;
+	audit_regions(
+			[this, &device, &searchpath] (rom_entry const *region, rom_entry const *rom) -> audit_record const *
+			{
+				if (ROMREGION_ISROMDATA(region))
+				{
+					if (searchpath.empty())
+						searchpath = device.searchpath();
+					return &audit_one_rom(searchpath, rom);
+				}
+				else if (ROMREGION_ISDISKDATA(region))
+				{
+					return &audit_one_disk(rom, device);
+				}
+				else
+				{
+					return nullptr;
+				}
+			},
+			rom_first_region(device),
+			found,
+			required);
 
 	if ((found == 0) && (required > 0))
 	{
@@ -147,7 +168,7 @@ media_auditor::summary media_auditor::audit_device(device_t &device, const char
 //-------------------------------------------------
 //  audit_software
 //-------------------------------------------------
-media_auditor::summary media_auditor::audit_software(const std::string &list_name, const software_info *swinfo, const char *validation)
+media_auditor::summary media_auditor::audit_software(software_list_device &swlist, const software_info &swinfo, const char *validation)
 {
 	// start fresh
 	m_record_list.clear();
@@ -155,21 +176,57 @@ media_auditor::summary media_auditor::audit_software(const std::string &list_nam
 	// store validation for later
 	m_validation = validation;
 
-	std::string combinedpath(util::string_format("%s;%s%s%s", swinfo->shortname(), list_name, PATH_SEPARATOR, swinfo->shortname()));
-	std::string locationtag(util::string_format("%s%%%s%%", list_name, swinfo->shortname()));
-	if (!swinfo->parentname().empty())
-	{
-		locationtag.append(swinfo->parentname());
-		combinedpath.append(util::string_format(";%s;%s%s%s", swinfo->parentname(), list_name, PATH_SEPARATOR, swinfo->parentname()));
-	}
-	m_searchpath = combinedpath;
-
 	std::size_t found = 0;
 	std::size_t required = 0;
 
 	// now iterate over software parts
-	for (const software_part &part : swinfo->parts())
-		audit_regions(part.romdata().data(), locationtag.c_str(), found, required);
+	std::vector<std::string> searchpath;
+	auto const do_audit =
+			[this, &swlist, &swinfo, &searchpath] (rom_entry const *region, rom_entry const *rom) -> audit_record const *
+			{
+				if (ROMREGION_ISROMDATA(region))
+				{
+					if (searchpath.empty())
+					{
+						std::vector<software_info const *> parents;
+
+						// search <rompath>/<list>/<software> following parents
+						searchpath.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), swinfo.shortname()));
+						for (software_info const *i = &swinfo; i && !i->parentname().empty(); i = swlist.find(i->parentname()))
+						{
+							if (std::find(parents.begin(), parents.end(), i) != parents.end())
+							{
+								osd_printf_warning("WARNING: software parent/clone relationships form a loop (%s:%s)\n", swlist.list_name(), swinfo.shortname());
+								break;
+							}
+							parents.emplace_back(i);
+							searchpath.emplace_back(util::string_format("%s" PATH_SEPARATOR "%s", swlist.list_name(), i->parentname()));
+						}
+
+						// search <rompath>/<software> following parents
+						searchpath.emplace_back(swinfo.shortname());
+						parents.clear();
+						for (software_info const *i = &swinfo; i && !i->parentname().empty(); i = swlist.find(i->parentname()))
+						{
+							if (std::find(parents.begin(), parents.end(), i) != parents.end())
+								break;
+							parents.emplace_back(i);
+							searchpath.emplace_back(i->parentname());
+						}
+					}
+					return &audit_one_rom(searchpath, rom);
+				}
+				else if (ROMREGION_ISDISKDATA(region))
+				{
+					return &audit_one_disk(rom, swlist, swinfo);
+				}
+				else
+				{
+					return nullptr;
+				}
+			};
+	for (const software_part &part : swinfo.parts())
+		audit_regions(do_audit, part.romdata().data(), found, required);
 
 	if ((found == 0) && (required > 0))
 	{
@@ -178,7 +235,7 @@ media_auditor::summary media_auditor::audit_software(const std::string &list_nam
 	}
 
 	// return a summary
-	return summarize(list_name.c_str());
+	return summarize(swlist.list_name().c_str());
 }
 
 
@@ -342,25 +399,22 @@ media_auditor::summary media_auditor::summarize(const char *name, std::ostream *
 //  audit_regions - validate/count for regions
 //-------------------------------------------------
 
-void media_auditor::audit_regions(const rom_entry *region, const char *locationtag, std::size_t &found, std::size_t &required)
+template <typename T>
+void media_auditor::audit_regions(T do_audit, const rom_entry *region, std::size_t &found, std::size_t &required)
 {
 	// now iterate over regions
+	std::vector<std::string> searchpath;
 	for ( ; region; region = rom_next_region(region))
 	{
 		// now iterate over rom definitions
-		for (const rom_entry *rom = rom_first_file(region); rom; rom = rom_next_file(rom))
+		for (rom_entry const *rom = rom_first_file(region); rom; rom = rom_next_file(rom))
 		{
-			util::hash_collection const hashes(ROM_GETHASHDATA(rom));
-
 			// count the number of files with hashes
+			util::hash_collection const hashes(ROM_GETHASHDATA(rom));
 			if (!hashes.flag(util::hash_collection::FLAG_NO_DUMP) && !ROM_ISOPTIONAL(rom))
 				required++;
 
-			audit_record const *record = nullptr;
-			if (ROMREGION_ISROMDATA(region))
-				record = &audit_one_rom(rom);
-			else if (ROMREGION_ISDISKDATA(region))
-				record = &audit_one_disk(rom, locationtag);
+			audit_record const *const record = do_audit(region, rom);
 
 			// count the number of files that are found.
 			if (record && ((record->status() == audit_status::GOOD) || (record->status() == audit_status::FOUND_INVALID)))
@@ -374,7 +428,7 @@ void media_auditor::audit_regions(const rom_entry *region, const char *locationt
 //  audit_one_rom - validate a single ROM entry
 //-------------------------------------------------
 
-media_auditor::audit_record &media_auditor::audit_one_rom(const rom_entry *rom)
+media_auditor::audit_record &media_auditor::audit_one_rom(const std::vector<std::string> &searchpath, const rom_entry *rom)
 {
 	// allocate and append a new record
 	audit_record &record = *m_record_list.emplace(m_record_list.end(), *rom, media_type::ROM);
@@ -384,27 +438,19 @@ media_auditor::audit_record &media_auditor::audit_one_rom(const rom_entry *rom)
 	bool const has_crc = record.expected_hashes().crc(crc);
 
 	// find the file and checksum it, getting the file length along the way
-	emu_file file(m_enumerator.options().media_path(), OPEN_FLAG_READ | OPEN_FLAG_NO_PRELOAD);
-	file.set_restrict_to_mediapath(true);
-	path_iterator path(m_searchpath);
-	std::string curpath;
-	// FIXME: needs to be adjusted to match ROM loading behaviour
-	while (path.next(curpath, record.name()))
-	{
-		// open the file if we can
-		osd_file::error filerr;
-		if (has_crc)
-			filerr = file.open(curpath, crc);
-		else
-			filerr = file.open(curpath);
+	emu_file file(m_enumerator.options().media_path(), searchpath, OPEN_FLAG_READ | OPEN_FLAG_NO_PRELOAD);
+	file.set_restrict_to_mediapath(1);
 
-		// if it worked, get the actual length and hashes, then stop
-		if (filerr == osd_file::error::NONE)
-		{
-			record.set_actual(file.hashes(m_validation), file.size());
-			break;
-		}
-	}
+	// open the file if we can
+	osd_file::error filerr;
+	if (has_crc)
+		filerr = file.open(record.name(), crc);
+	else
+		filerr = file.open(record.name());
+
+	// if it worked, get the actual length and hashes, then stop
+	if (filerr == osd_file::error::NONE)
+		record.set_actual(file.hashes(m_validation), file.size());
 
 	// compute the final status
 	compute_status(record, rom, record.actual_length() != 0);
@@ -416,14 +462,15 @@ media_auditor::audit_record &media_auditor::audit_one_rom(const rom_entry *rom)
 //  audit_one_disk - validate a single disk entry
 //-------------------------------------------------
 
-media_auditor::audit_record &media_auditor::audit_one_disk(const rom_entry *rom, const char *locationtag)
+template <typename... T>
+media_auditor::audit_record &media_auditor::audit_one_disk(const rom_entry *rom, T &&... args)
 {
 	// allocate and append a new record
 	audit_record &record = *m_record_list.emplace(m_record_list.end(), *rom, media_type::DISK);
 
 	// open the disk
 	chd_file source;
-	chd_error err = chd_error(open_disk_image(m_enumerator.options(), &m_enumerator.driver(), rom, source, locationtag));
+	const chd_error err = rom_load_manager::open_disk_image(m_enumerator.options(), std::forward<T>(args)..., rom, source);
 
 	// if we succeeded, get the hashes
 	if (err == CHDERR_NONE)
diff --git a/src/frontend/mame/audit.h b/src/frontend/mame/audit.h
index 42296d9260b..511b4c98845 100644
--- a/src/frontend/mame/audit.h
+++ b/src/frontend/mame/audit.h
@@ -7,12 +7,11 @@
     ROM, disk, and sample auditing functions.
 
 ***************************************************************************/
-
-#pragma once
-
 #ifndef MAME_FRONTEND_AUDIT_H
 #define MAME_FRONTEND_AUDIT_H
 
+#pragma once
+
 #include "hash.h"
 
 #include <iosfwd>
@@ -38,6 +37,7 @@
 
 // forward declarations
 class driver_enumerator;
+class software_list_device;
 
 
 
@@ -137,15 +137,15 @@ public:
 
 	private:
 		// internal state
-		media_type          m_type;                 // type of item that was audited
-		audit_status        m_status;               // status of audit on this item
-		audit_substatus     m_substatus;            // finer-detail status
-		const char *        m_name;                 // name of item
-		uint64_t            m_explength;            // expected length of item
-		uint64_t            m_length;               // actual length of item
-		util::hash_collection     m_exphashes;            // expected hash data
-		util::hash_collection     m_hashes;               // actual hash information
-		device_t *          m_shared_device;        // device that shares the rom
+		media_type              m_type;                 // type of item that was audited
+		audit_status            m_status;               // status of audit on this item
+		audit_substatus         m_substatus;            // finer-detail status
+		const char *            m_name;                 // name of item
+		uint64_t                m_explength;            // expected length of item
+		uint64_t                m_length;               // actual length of item
+		util::hash_collection   m_exphashes;            // expected hash data
+		util::hash_collection   m_hashes;               // actual hash information
+		device_t *              m_shared_device;        // device that shares the rom
 	};
 	using record_list = std::list<audit_record>;
 
@@ -158,15 +158,15 @@ public:
 	// audit operations
 	summary audit_media(const char *validation = AUDIT_VALIDATE_FULL);
 	summary audit_device(device_t &device, const char *validation = AUDIT_VALIDATE_FULL);
-	summary audit_software(const std::string &list_name, const software_info *swinfo, const char *validation = AUDIT_VALIDATE_FULL);
+	summary audit_software(software_list_device &swlist, const software_info &swinfo, const char *validation = AUDIT_VALIDATE_FULL);
 	summary audit_samples();
 	summary summarize(const char *name, std::ostream *output = nullptr) const;
 
 private:
 	// internal helpers
-	void audit_regions(const rom_entry *region, const char *locationtag, std::size_t &found, std::size_t &required);
-	audit_record &audit_one_rom(const rom_entry *rom);
-	audit_record &audit_one_disk(const rom_entry *rom, const char *locationtag);
+	template <typename T> void audit_regions(T do_audit, const rom_entry *region, std::size_t &found, std::size_t &required);
+	audit_record &audit_one_rom(const std::vector<std::string> &searchpath, const rom_entry *rom);
+	template <typename... T> audit_record &audit_one_disk(const rom_entry *rom, T &&... args);
 	void compute_status(audit_record &record, const rom_entry *rom, bool found);
 	device_t *find_shared_device(device_t &device, const char *name, const util::hash_collection &romhashes, uint64_t romlength);
 
@@ -174,7 +174,6 @@ private:
 	record_list                 m_record_list;
 	const driver_enumerator &   m_enumerator;
 	const char *                m_validation;
-	std::string                 m_searchpath;
 };
 
 
diff --git a/src/frontend/mame/clifront.cpp b/src/frontend/mame/clifront.cpp
index fa63a283465..aa5ec7606b8 100644
--- a/src/frontend/mame/clifront.cpp
+++ b/src/frontend/mame/clifront.cpp
@@ -1279,7 +1279,7 @@ void cli_frontend::verifysoftware(const std::vector<std::string> &args)
 						nrlists++;
 						for (const software_info &swinfo : swlistdev.get_info())
 						{
-							media_auditor::summary summary = auditor.audit_software(swlistdev.list_name(), &swinfo, AUDIT_VALIDATE_FAST);
+							media_auditor::summary summary = auditor.audit_software(swlistdev, swinfo, AUDIT_VALIDATE_FAST);
 
 							print_summary(
 									auditor, summary, false,
@@ -1386,7 +1386,7 @@ void cli_frontend::verifysoftlist(const std::vector<std::string> &args)
 					// Get the actual software list contents
 					for (const software_info &swinfo : swlistdev.get_info())
 					{
-						media_auditor::summary summary = auditor.audit_software(swlistdev.list_name(), &swinfo, AUDIT_VALIDATE_FAST);
+						media_auditor::summary summary = auditor.audit_software(swlistdev, swinfo, AUDIT_VALIDATE_FAST);
 
 						print_summary(
 								auditor, summary, false,
diff --git a/src/frontend/mame/ui/imgcntrl.cpp b/src/frontend/mame/ui/imgcntrl.cpp
index 8d3ef0974c1..c0b5c44f1af 100644
--- a/src/frontend/mame/ui/imgcntrl.cpp
+++ b/src/frontend/mame/ui/imgcntrl.cpp
@@ -138,7 +138,7 @@ void menu_control_device_image::load_software_part()
 	driver_enumerator drivlist(machine().options(), machine().options().system_name());
 	drivlist.next();
 	media_auditor auditor(drivlist);
-	media_auditor::summary summary = auditor.audit_software(m_sld->list_name(), (software_info *)m_swi, AUDIT_VALIDATE_FAST);
+	media_auditor::summary summary = auditor.audit_software(*m_sld, *m_swi, AUDIT_VALIDATE_FAST);
 	// if everything looks good, load software
 	if (summary == media_auditor::CORRECT || summary == media_auditor::BEST_AVAILABLE || summary == media_auditor::NONE_NEEDED)
 	{
diff --git a/src/frontend/mame/ui/selgame.cpp b/src/frontend/mame/ui/selgame.cpp
index 6bbe0c874f1..1f7603b4f31 100644
--- a/src/frontend/mame/ui/selgame.cpp
+++ b/src/frontend/mame/ui/selgame.cpp
@@ -897,7 +897,7 @@ void menu_select_game::inkey_select_favorite(const event *menu_event)
 		software_list_device *swlist = software_list_device::find_by_name(*drv.config(), ui_swinfo->listname);
 		const software_info *swinfo = swlist->find(ui_swinfo->shortname);
 
-		media_auditor::summary const summary = auditor.audit_software(swlist->list_name(), swinfo, AUDIT_VALIDATE_FAST);
+		media_auditor::summary const summary = auditor.audit_software(*swlist, *swinfo, AUDIT_VALIDATE_FAST);
 
 		if (summary == media_auditor::CORRECT || summary == media_auditor::BEST_AVAILABLE || summary == media_auditor::NONE_NEEDED)
 		{
diff --git a/src/frontend/mame/ui/selmenu.cpp b/src/frontend/mame/ui/selmenu.cpp
index 4fd71e2798e..92bdd3ada64 100644
--- a/src/frontend/mame/ui/selmenu.cpp
+++ b/src/frontend/mame/ui/selmenu.cpp
@@ -2282,8 +2282,7 @@ void menu_select_launch::arts_render(float origx1, float origy1, float origx2, f
 		// loads the image if necessary
 		if (!m_cache->snapx_driver_is(driver) || !snapx_valid() || m_switch_image)
 		{
-			emu_file snapfile(searchstr.c_str(), OPEN_FLAG_READ);
-			snapfile.set_restrict_to_mediapath(true);
+			emu_file snapfile(searchstr, OPEN_FLAG_READ);
 			bitmap_argb32 tmp_bitmap;
 
 			// try to load snapshot first from saved "0000.png" file
diff --git a/src/frontend/mame/ui/selsoft.cpp b/src/frontend/mame/ui/selsoft.cpp
index 4bbfb6fd294..84fa109bea6 100644
--- a/src/frontend/mame/ui/selsoft.cpp
+++ b/src/frontend/mame/ui/selsoft.cpp
@@ -486,7 +486,7 @@ void menu_select_software::inkey_select(const event *menu_event)
 		software_list_device *swlist = software_list_device::find_by_name(*drivlist.config(), ui_swinfo->listname);
 		const software_info *swinfo = swlist->find(ui_swinfo->shortname);
 
-		media_auditor::summary const summary = auditor.audit_software(swlist->list_name(), swinfo, AUDIT_VALIDATE_FAST);
+		media_auditor::summary const summary = auditor.audit_software(*swlist, *swinfo, AUDIT_VALIDATE_FAST);
 
 		if (summary == media_auditor::CORRECT || summary == media_auditor::BEST_AVAILABLE || summary == media_auditor::NONE_NEEDED)
 		{
diff --git a/src/mame/mame.lst b/src/mame/mame.lst
index ea8d18c018a..885557eb4df 100644
--- a/src/mame/mame.lst
+++ b/src/mame/mame.lst
@@ -39926,7 +39926,7 @@ tvcapcom                        //
 theboat                         //
 
 @source:tvgame.cpp
-tvgame                          //
+tvgame                          // 2011
 
 @source:twin16.cpp
 cuebrickj                       // GX903 (c) 1989 (Japan)