[PATCH][BUG FIX] Pointer arithmetic with NULL

[Ranier Vilela]

Hi,
Pointer addition with NULL, is technically undefined behavior.

Best regards.
Ranier Vilela

--- \dll\postgresql-12.0\a\backend\access\transam\xlog.c        Mon Sep 30 
17:06:55 2019
+++ xlog.c      Fri Nov 22 13:57:17 2019
@@ -1861,7 +1861,7 @@
        {
                Assert(((XLogPageHeader) cachedPos)->xlp_magic == 
XLOG_PAGE_MAGIC);
                Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr 
% XLOG_BLCKSZ));
-               return cachedPos + ptr % XLOG_BLCKSZ;
+               return ptr % XLOG_BLCKSZ;
        }
 
        /*

xlog.c.patch
Description: xlog.c.patch