Fix core dump due to null-pointer dereference in to_char() when datetime

format codes are misapplied to a numeric argument.  (The code still produces
a pretty bogus error message in such cases, but I'll settle for stopping the
crash for now.)  Per bug #4700 from Sergey Burladyan.

Problem exists in all supported branches, so patch all the way back.
In HEAD, also clean up some ugly coding in the nearby cache management
code.

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 6d69ce1b9883a6a02d07d7d0f9d9b9231e6abf32..f82fd2b25bebcb74eaf47aab531b8728a421e880 100644 (file)
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -347,7 +347,7 @@ static int  DCHCounter = 0;
 
 /* global cache for --- number part */
 static NUMCacheEntry NUMCache[NUM_CACHE_FIELDS + 1];
-static NUMCacheEntry *last_NUMCacheEntry;
+static NUMCacheEntry *last_NUMCacheEntry = NUMCache + 0;
 
 static int     n_NUMCache = 0;         /* number of entries */
 static int     NUMCounter = 0;