diff --git a/src/undo.c b/src/undo.c
index 8c2783a..52df939 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -361,6 +361,7 @@
 {
     char_u *line = ml_get(lnum);
 
+    ul->ul_textlen = ml_get_len(lnum);
     if (curbuf->b_ml.ml_line_len == 0)
     {
 	ul->ul_len = 1;
@@ -793,14 +794,10 @@
 {
     context_sha256_T	ctx;
     linenr_T		lnum;
-    char_u		*p;
 
     sha256_start(&ctx);
     for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum)
-    {
-	p = ml_get(lnum);
-	sha256_update(&ctx, p, (UINT32_T)(STRLEN(p) + 1));
-    }
+	sha256_update(&ctx, ml_get(lnum), (UINT32_T)(ml_get_len(lnum) + 1));
     sha256_finish(&ctx, hash);
 }
 
@@ -820,8 +817,10 @@
     char_u	*undo_file_name = NULL;
     int		dir_len;
     char_u	*p;
+    size_t	plen;
     stat_T	st;
     char_u	*ffname = buf_ffname;
+    size_t	ffnamelen;
 #ifdef HAVE_READLINK
     char_u	fname_buf[MAXPATHL];
 #endif
@@ -836,6 +835,7 @@
 	ffname = fname_buf;
 #endif
 
+    ffnamelen = STRLEN(ffname);
     // Loop over 'undodir'.  When reading find the first file that exists.
     // When not reading use the first directory that exists or ".".
     dirp = p_udir;
@@ -846,23 +846,24 @@
 	{
 	    // Use same directory as the ffname,
 	    // "dir/name" -> "dir/.name.un~"
-	    undo_file_name = vim_strnsave(ffname, STRLEN(ffname) + 5);
+	    undo_file_name = vim_strnsave(ffname, ffnamelen + 5);
 	    if (undo_file_name == NULL)
 		break;
 	    p = gettail(undo_file_name);
+	    plen = (size_t)(ffnamelen - (p - undo_file_name));
 #ifdef VMS
 	    // VMS can not handle more than one dot in the filenames
 	    // use "dir/name" -> "dir/_un_name" - add _un_
 	    // at the beginning to keep the extension
-	    mch_memmove(p + 4,  p, STRLEN(p) + 1);
+	    mch_memmove(p + 4,  p, plen + 1);
 	    mch_memmove(p, "_un_", 4);
 
 #else
 	    // Use same directory as the ffname,
 	    // "dir/name" -> "dir/.name.un~"
-	    mch_memmove(p + 1, p, STRLEN(p) + 1);
+	    mch_memmove(p + 1, p, plen + 1);
 	    *p = '.';
-	    STRCAT(p, ".un~");
+	    STRCPY(p + plen + 1, ".un~");
 #endif
 	}
 	else
@@ -872,7 +873,7 @@
 	    {
 		if (munged_name == NULL)
 		{
-		    munged_name = vim_strsave(ffname);
+		    munged_name = vim_strnsave(ffname, ffnamelen);
 		    if (munged_name == NULL)
 			return NULL;
 		    for (p = munged_name; *p != NUL; MB_PTR_ADV(p))
@@ -1189,7 +1190,6 @@
     static int
 serialize_header(bufinfo_T *bi, char_u *hash)
 {
-    long	len;
     buf_T	*buf = bi->bi_buf;
     FILE	*fp = bi->bi_fp;
     char_u	time_buf[8];
@@ -1205,6 +1205,7 @@
     {
 	char_u *header;
 	int    header_len;
+	long	len;
 
 	undo_write_bytes(bi, (long_u)UF_VERSION_CRYPT, 2);
 	bi->bi_state = crypt_create_for_writing(crypt_get_method_nr(buf),
@@ -1244,11 +1245,9 @@
 
     // buffer-specific data
     undo_write_bytes(bi, (long_u)buf->b_ml.ml_line_count, 4);
-    len = buf->b_u_line_ptr.ul_line == NULL
-				? 0L : (long)STRLEN(buf->b_u_line_ptr.ul_line);
-    undo_write_bytes(bi, (long_u)len, 4);
-    if (len > 0 && fwrite_crypt(bi, buf->b_u_line_ptr.ul_line, (size_t)len)
-								       == FAIL)
+    undo_write_bytes(bi, (long_u)buf->b_u_line_ptr.ul_textlen, 4);
+    if (buf->b_u_line_ptr.ul_textlen > 0 && fwrite_crypt(bi, buf->b_u_line_ptr.ul_line,
+			(size_t)buf->b_u_line_ptr.ul_textlen) == FAIL)
 	return FAIL;
     undo_write_bytes(bi, (long_u)buf->b_u_line_lnum, 4);
     undo_write_bytes(bi, (long_u)buf->b_u_line_colnr, 4);
@@ -1415,7 +1414,6 @@
     u_entry_T	*uep)
 {
     int		i;
-    size_t	len;
 
     undo_write_bytes(bi, (long_u)uep->ue_top, 4);
     undo_write_bytes(bi, (long_u)uep->ue_bot, 4);
@@ -1425,10 +1423,10 @@
     {
 	// Text is written without the text properties, since we cannot restore
 	// the text property types.
-	len = STRLEN(uep->ue_array[i].ul_line);
-	if (undo_write_bytes(bi, (long_u)len, 4) == FAIL)
+	if (undo_write_bytes(bi, (long_u)uep->ue_array[i].ul_textlen, 4) == FAIL)
 	    return FAIL;
-	if (len > 0 && fwrite_crypt(bi, uep->ue_array[i].ul_line, len) == FAIL)
+	if (uep->ue_array[i].ul_textlen > 0
+		&& fwrite_crypt(bi, uep->ue_array[i].ul_line, uep->ue_array[i].ul_textlen) == FAIL)
 	    return FAIL;
     }
     return OK;
@@ -1484,6 +1482,7 @@
 	}
 	array[i].ul_line = line;
 	array[i].ul_len = line_len + 1;
+	array[i].ul_textlen = line_len;
     }
     return uep;
 }
@@ -1862,6 +1861,7 @@
 
     CLEAR_FIELD(bi);
     line_ptr.ul_len = 0;
+    line_ptr.ul_textlen = 0;
     line_ptr.ul_line = NULL;
 
     if (name == NULL)
@@ -1986,6 +1986,7 @@
     {
 	line_ptr.ul_line = read_string_decrypt(&bi, str_len);
 	line_ptr.ul_len = str_len + 1;
+	line_ptr.ul_textlen = str_len;
     }
     line_lnum = (linenr_T)undo_read_4c(&bi);
     line_colnr = (colnr_T)undo_read_4c(&bi);
@@ -3098,7 +3099,7 @@
     int		mark;
     int		nomark;
     int		changes = 1;
-    int		i;
+    int		len;
 
     /*
      * 1: walk the tree to find all leafs, put the info in "ga".
@@ -3117,18 +3118,20 @@
 	{
 	    if (ga_grow(&ga, 1) == FAIL)
 		break;
-	    vim_snprintf((char *)IObuff, IOSIZE, "%6ld %7d  ",
+	    len = vim_snprintf((char *)IObuff, IOSIZE, "%6ld %7d  ",
 							uhp->uh_seq, changes);
-	    add_time(IObuff + STRLEN(IObuff), IOSIZE - STRLEN(IObuff),
-								uhp->uh_time);
+	    add_time(IObuff + len, IOSIZE - len, uhp->uh_time);
+
+	    // we have to call STRLEN() here because add_time() does not report
+	    // the number of characters added.
+	    len += STRLEN(IObuff + len);
 	    if (uhp->uh_save_nr > 0)
 	    {
-		while (STRLEN(IObuff) < 33)
-		    STRCAT(IObuff, " ");
-		vim_snprintf_add((char *)IObuff, IOSIZE,
-						   "  %3ld", uhp->uh_save_nr);
+		int n = (len >= 33) ? 0 : 33 - len;
+
+		len += vim_snprintf((char *)IObuff + len, IOSIZE - len, "%*.*s  %3ld", n, n, " ", uhp->uh_save_nr);
 	    }
-	    ((char_u **)(ga.ga_data))[ga.ga_len++] = vim_strsave(IObuff);
+	    ((char_u **)(ga.ga_data))[ga.ga_len++] = vim_strnsave(IObuff, len);
 	}
 
 	uhp->uh_walk = mark;
@@ -3175,6 +3178,8 @@
 	msg(_("Nothing to undo"));
     else
     {
+	int		i;
+
 	sort_strings((char_u **)ga.ga_data, ga.ga_len);
 
 	msg_start();
@@ -3481,6 +3486,7 @@
     buf->b_u_numhead = 0;
     buf->b_u_line_ptr.ul_line = NULL;
     buf->b_u_line_ptr.ul_len = 0;
+    buf->b_u_line_ptr.ul_textlen = 0;
     buf->b_u_line_lnum = 0;
 }
 
@@ -3540,6 +3546,7 @@
 
     VIM_CLEAR(curbuf->b_u_line_ptr.ul_line);
     curbuf->b_u_line_ptr.ul_len = 0;
+    curbuf->b_u_line_ptr.ul_textlen = 0;
     curbuf->b_u_line_lnum = 0;
 }