patch 7.4.2101
Problem:    Looping over windows, buffers and tab pages is inconsistant.
Solution:   Use FOR_ALL_ macros everywhere. (Yegappan Lakshmanan)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index ec347c1..ae17038 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -1439,7 +1439,7 @@
 	{
 	    /* No full path name match, try a match with a URL or a "nofile"
 	     * buffer, these don't use the full path. */
-	    for (buf = firstbuf; buf != NULL; buf = buf->b_next)
+	    FOR_ALL_BUFFERS(buf)
 		if (buf->b_fname != NULL
 			&& (path_with_url(buf->b_fname)
 #ifdef FEAT_QUICKFIX
@@ -1597,7 +1597,7 @@
     ++emsg_off;
     buf = get_buf_tv(&argvars[0], TRUE);
 #ifdef FEAT_WINDOWS
-    for (wp = firstwin; wp; wp = wp->w_next)
+    FOR_ALL_WINDOWS(wp)
     {
 	++winnr;
 	if (wp->w_buffer == buf)
@@ -6383,7 +6383,7 @@
     int		n = 0;
     buf_T	*buf;
 
-    for (buf = firstbuf; buf != NULL; buf = buf->b_next)
+    FOR_ALL_BUFFERS(buf)
 	if (n < buf->b_fnum)
 	    n = buf->b_fnum;
 
@@ -12373,7 +12373,7 @@
     char_u	buf[50];
 
     ga_init2(&ga, (int)sizeof(char), 70);
-    for (wp = firstwin; wp != NULL; wp = wp->w_next)
+    FOR_ALL_WINDOWS(wp)
     {
 	sprintf((char *)buf, "%dresize %d|", winnr, wp->w_height);
 	ga_concat(&ga, buf);