File string-compare.diff of Package libapr2

--- strings/apr_snprintf.c
+++ strings/apr_snprintf.c
@@ -1258,7 +1258,7 @@ APR_DECLARE(int) apr_vformatter(int (*fl
                 break;
             }
 
-            if (prefix_char != NUL && s != S_NULL && s != char_buf) {
+            if (prefix_char != NUL && strcmp(s, S_NULL) && s != char_buf) {
                 *--s = prefix_char;
                 s_len++;
             }