diff --git a/meson.build b/meson.build
index f594ae71..e87c647a 100644
--- a/meson.build
+++ b/meson.build
@@ -660,7 +660,6 @@ script_sources = files('./doc/create-doxygen-lua-api.sh',
 './scripts/authors.sh',
 './scripts/check-compiles.sh',
 './scripts/doxygen-help.sh',
-'./scripts/doxygen.sh',
 './scripts/generate-ClayRGB1998-icc-h.sh',
 './scripts/generate-appimage.sh',
 './scripts/generate-linuxdeploy-for-arm.sh',
diff --git a/src/collect.cc b/src/collect.cc
index 57f3387a..e91c8b08 100644
--- a/src/collect.cc
+++ b/src/collect.cc
@@ -204,20 +204,17 @@ GList *collection_list_sort(GList *list, SortType method)
 
 GList *collection_list_randomize(GList *list)
 {
-	guint random, length, i;
+	guint length, i;
 	gpointer tmp;
 	GList *nlist, *olist;
 
 	length = g_list_length(list);
 	if (!length) return nullptr;
 
-	srand(static_cast<unsigned int>(time(nullptr))); // Initialize random generator (hasn't to be that much strong)
-
 	for (i = 0; i < length; i++)
 		{
-		random = static_cast<guint>(1.0 * length * rand()/(RAND_MAX + 1.0));
 		olist = g_list_nth(list, i);
-		nlist = g_list_nth(list, random);
+		nlist = g_list_nth(list, g_random_int_range(0, length));
 		tmp = olist->data;
 		olist->data = nlist->data;
 		nlist->data = tmp;
diff --git a/src/exif-common.cc b/src/exif-common.cc
index ac95a855..bbb63cd0 100644
--- a/src/exif-common.cc
+++ b/src/exif-common.cc
@@ -211,7 +211,7 @@ static gchar *exif_build_formatted_DateTime(ExifData *exif)
 	memset(&tm, 0, sizeof(tm)); /* Uh, strptime could let garbage in tm! */
 	if (text && strptime(text, "%Y:%m:%d %H:%M:%S", &tm))
 		{
-		buflen = strftime(buf, sizeof(buf), "%x %X", &tm);
+		buflen = strftime(buf, sizeof(buf), "%F %X", &tm);
 		if (buflen > 0)
 			{
 			tmp = g_locale_to_utf8(buf, buflen, nullptr, nullptr, &error);
@@ -262,7 +262,7 @@ static gchar *exif_build_formatted_DateTimeDigitized(ExifData *exif)
 	memset(&tm, 0, sizeof(tm)); /* Uh, strptime could let garbage in tm! */
 	if (text && strptime(text, "%Y:%m:%d %H:%M:%S", &tm))
 		{
-		buflen = strftime(buf, sizeof(buf), "%x %X", &tm);
+		buflen = strftime(buf, sizeof(buf), "%F %X", &tm);
 		if (buflen > 0)
 			{
 			tmp = g_locale_to_utf8(buf, buflen, nullptr, nullptr, &error);
@@ -788,7 +788,7 @@ static gchar *exif_build_formatted_localtime(ExifData *exif)
 			tm_local = localtime(&stamp);
 
 			/* Convert to localtime using locale */
-			buflen = strftime(buf, sizeof(buf), "%x %X", tm_local);
+			buflen = strftime(buf, sizeof(buf), "%F %X", tm_local);
 			if (buflen > 0)
 				{
 				tmp = g_locale_to_utf8(buf, buflen, nullptr, nullptr, &error);
diff --git a/src/filedata.cc b/src/filedata.cc
index 52d348af..4e441c53 100644
--- a/src/filedata.cc
+++ b/src/filedata.cc
@@ -136,7 +136,7 @@ const gchar *text_from_time(time_t t)
 	btime = localtime(&t);
 
 	/* the %x warning about 2 digit years is not an error */
-	buflen = strftime(buf, sizeof(buf), "%x %X", btime);
+	buflen = strftime(buf, sizeof(buf), "%F %X", btime);
 	if (buflen < 1) return "";
 
 	g_free(ret);
@@ -705,7 +705,9 @@ void file_data_dump()
 		{
 		list = g_hash_table_get_values(file_data_pool);
 
+#ifdef DEBUG_FILEDATA
 		log_printf("%d", global_file_data_count);
+#endif
 		log_printf("%d", g_list_length(list));
 
 		while (list)
diff --git a/src/filedata.h b/src/filedata.h
index 49a1476f..39992652 100644
--- a/src/filedata.h
+++ b/src/filedata.h
@@ -22,9 +22,7 @@
 #ifndef FILEDATA_H
 #define FILEDATA_H
 
-#ifdef DEBUG
-#define DEBUG_FILEDATA
-#endif
+#undef DEBUG_FILEDATA
 
 #define FD_MAGICK 0x12345678u
 
diff --git a/src/image-load-heif.cc b/src/image-load-heif.cc
index 68de7f75..d4a89b90 100644
--- a/src/image-load-heif.cc
+++ b/src/image-load-heif.cc
@@ -63,7 +63,7 @@ static gboolean image_loader_heif_load(gpointer loader, const guchar *buf, gsize
 	error_code = heif_context_read_from_memory_without_copy(ctx, buf, count, NULL);
 	if (error_code.code)
 		{
-		log_printf("warning: heif reader error: %s\n", error_code.message);
+		log_printf("warning: heif (heif_context_read_from_memory_without_copy) reader error: %s\n", error_code.message);
 		heif_context_free(ctx);
 		return FALSE;
 		}
@@ -80,7 +80,7 @@ static gboolean image_loader_heif_load(gpointer loader, const guchar *buf, gsize
 		error_code = heif_context_get_image_handle(ctx, IDs[ld->page_num], &handle);
 		if (error_code.code)
 			{
-			log_printf("warning:  heif reader error: %s\n", error_code.message);
+			log_printf("warning:  heif (heif_context_get_image_handle) reader error: %s\n", error_code.message);
 			heif_context_free(ctx);
 			return FALSE;
 			}
@@ -89,7 +89,7 @@ static gboolean image_loader_heif_load(gpointer loader, const guchar *buf, gsize
 		error_code = heif_decode_image(handle, &img, heif_colorspace_RGB, heif_chroma_interleaved_24bit, NULL);
 		if (error_code.code)
 			{
-			log_printf("warning: heif reader error: %s\n", error_code.message);
+			log_printf("warning: heif (heif_decode_image) reader error: %s\n", error_code.message);
 			heif_context_free(ctx);
 			return FALSE;
 			}
diff --git a/src/image-load.cc b/src/image-load.cc
index 7f743ec9..18203013 100644
--- a/src/image-load.cc
+++ b/src/image-load.cc
@@ -1063,7 +1063,7 @@ static gboolean image_loader_setup_source(ImageLoader *il)
 			return FALSE;
 			}
 
-		il->mapped_file = static_cast<guchar *>(mmap(nullptr, il->bytes_total, PROT_READ|PROT_WRITE, MAP_PRIVATE, load_fd, 0));
+		il->mapped_file = static_cast<guchar *>(mmap(nullptr, il->bytes_total, PROT_READ, MAP_PRIVATE, load_fd, 0));
 		close(load_fd);
 		if (il->mapped_file == MAP_FAILED)
 			{
diff --git a/src/main.cc b/src/main.cc
index ac6f97fb..85baee74 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -1303,10 +1303,6 @@ gint main(gint argc, gchar *argv[])
 #ifdef HAVE_LUA
 	lua_init();
 #endif
-
-	/* setup random seed for random slideshow */
-	srand(time(nullptr));
-
 #if 0
 	/* See later comment; this handler leads to UB. */
 	setup_sigbus_handler();
diff --git a/src/slideshow.cc b/src/slideshow.cc
index 0cf242df..6d1369e6 100644
--- a/src/slideshow.cc
+++ b/src/slideshow.cc
@@ -102,10 +102,9 @@ static void ptr_array_random_shuffle(GPtrArray *array)
 {
 	guint i;
 	for (i = 0; i < array->len; ++i)
-		{
-		guint p = static_cast<double>(rand()) / (static_cast<double>(RAND_MAX) + 1.0) * array->len;
-		swap(array, i, p);
-		}
+	{
+		swap(array, i, g_random_int_range(0, array->len));
+	}
 }
 
 static GList *generate_random_list(SlideShowData *ss)
diff --git a/src/thumb-standard.cc b/src/thumb-standard.cc
index fa0c5bd0..e6f5b025 100644
--- a/src/thumb-standard.cc
+++ b/src/thumb-standard.cc
@@ -32,6 +32,7 @@
 #include "metadata.h"
 #include "color-man.h"
 
+#include <errno.h>
 
 /**
  * @file
@@ -231,9 +232,13 @@ static gboolean thumb_loader_std_fail_check(ThumbLoaderStd *tl)
 		if (pixbuf)
 			{
 			const gchar *mtime_str;
+			const gchar *size_str;
 
 			mtime_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_MTIME);
-			if (mtime_str && strtol(mtime_str, nullptr, 10) == tl->source_mtime)
+			size_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_SIZE);
+			if (mtime_str && size_str &&
+			    strtoll(mtime_str, NULL, 10) == tl->source_mtime &&
+			    strtoll(size_str, NULL, 10) == tl->source_size)
 				{
 				result = TRUE;
 				DEBUG_1("thumb fail valid: %s", tl->fd->path);
@@ -255,7 +260,9 @@ static gboolean thumb_loader_std_validate(ThumbLoaderStd *tl, GdkPixbuf *pixbuf)
 	const gchar *valid_uri;
 	const gchar *uri;
 	const gchar *mtime_str;
+	const gchar *size_str;
 	time_t mtime;
+	off_t fsize;
 	gint w, h;
 
 	if (!pixbuf) return FALSE;
@@ -270,12 +277,16 @@ static gboolean thumb_loader_std_validate(ThumbLoaderStd *tl, GdkPixbuf *pixbuf)
 
 	uri = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_URI);
 	mtime_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_MTIME);
+	size_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_SIZE);
 
-	if (!mtime_str || !uri || !valid_uri) return FALSE;
+	if (!mtime_str || !size_str || !uri || !valid_uri) return FALSE;
 	if (strcmp(uri, valid_uri) != 0) return FALSE;
 
-	mtime = strtol(mtime_str, nullptr, 10);
-	if (tl->source_mtime != mtime) return FALSE;
+	errno = 0;
+	mtime = strtoll(mtime_str, NULL, 10);
+	if (errno || tl->source_mtime != mtime) return FALSE;
+	fsize = strtoll(size_str, NULL, 10);
+	if (errno || tl->source_size != fsize) return FALSE;
 
 	return TRUE;
 }
@@ -344,6 +355,7 @@ static void thumb_loader_std_save(ThumbLoaderStd *tl, GdkPixbuf *pixbuf)
 		const gchar *mark_uri;
 		gchar *mark_app;
 		gchar *mark_mtime;
+		gchar *mark_size;
 		gchar *pathl;
 		gboolean success;
 
@@ -351,10 +363,12 @@ static void thumb_loader_std_save(ThumbLoaderStd *tl, GdkPixbuf *pixbuf)
 
 		mark_app = g_strdup_printf("%s %s", GQ_APPNAME, VERSION);
 		mark_mtime = g_strdup_printf("%llu", static_cast<unsigned long long>(tl->source_mtime));
+		mark_size = g_strdup_printf("%llu", static_cast<unsigned long long>(tl->source_size));
 		pathl = path_from_utf8(tmp_path);
 		success = gdk_pixbuf_save(pixbuf, pathl, "png", nullptr,
 					  THUMB_MARKER_URI, mark_uri,
 					  THUMB_MARKER_MTIME, mark_mtime,
+					  THUMB_MARKER_SIZE, mark_size,
 					  THUMB_MARKER_APP, mark_app,
 					  NULL);
 		if (success)
@@ -366,6 +380,7 @@ static void thumb_loader_std_save(ThumbLoaderStd *tl, GdkPixbuf *pixbuf)
 		g_free(pathl);
 
 		g_free(mark_mtime);
+		g_free(mark_size);
 		g_free(mark_app);
 
 		g_free(tmp_path);
@@ -931,10 +946,13 @@ static void thumb_loader_std_thumb_file_validate_done_cb(ThumbLoaderStd *UNUSED(
 		{
 		const gchar *uri;
 		const gchar *mtime_str;
+		const gchar *size_str;
 
 		uri = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_URI);
 		mtime_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_MTIME);
-		if (uri && mtime_str)
+		size_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_SIZE);
+
+		if (uri && mtime_str && size_str)
 			{
 			if (strncmp(uri, "file:", strlen("file:")) == 0)
 				{
@@ -943,7 +961,8 @@ static void thumb_loader_std_thumb_file_validate_done_cb(ThumbLoaderStd *UNUSED(
 
 				target = g_filename_from_uri(uri, nullptr, nullptr);
 				if (stat(target, &st) == 0 &&
-				    st.st_mtime == strtol(mtime_str, nullptr, 10))
+				    st.st_mtime == strtoll(mtime_str, NULL, 10) &&
+				    st.st_size == strtoll(size_str, NULL, 10))
 					{
 					valid = TRUE;
 					}
@@ -1098,11 +1117,13 @@ static void thumb_std_maint_move_validate_cb(const gchar *UNUSED(path), gboolean
 		{
 		const gchar *uri;
 		const gchar *mtime_str;
+		const gchar *size_str;
 
 		uri = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_URI);
 		mtime_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_MTIME);
+		size_str = gdk_pixbuf_get_option(pixbuf, THUMB_MARKER_SIZE);
 
-		if (uri && mtime_str && strcmp(uri, tm->source_uri) == 0)
+		if (uri && mtime_str && size_str && strcmp(uri, tm->source_uri) == 0)
 			{
 			gchar *pathl;
 
@@ -1116,7 +1137,8 @@ static void thumb_std_maint_move_validate_cb(const gchar *UNUSED(path), gboolean
 			tm->tl->cache_local = FALSE;
 			file_data_unref(tm->tl->fd);
 			tm->tl->fd = file_data_new_group(tm->dest);
-			tm->tl->source_mtime = strtol(mtime_str, nullptr, 10);
+			tm->tl->source_mtime = strtoll(mtime_str, NULL, 10);
+			tm->tl->source_size = strtoll(size_str, NULL, 10);
 
 			pathl = path_from_utf8(tm->tl->fd->path);
 			g_free(tm->tl->thumb_uri);