Bug#43572 Handle failures from hash_init

      
Failure to allocate memory for the hash->array element,
caused hash_init to return without initializing the other
members of the hash. Thus although the dynamic array
buffer may be allocated at a later point in the code, the
incompletely initialized hash caused fatal failures.

This patch moves the initialization of the other members
of the hash above the array allocation, so that the usage
of this hash will not result in fatal failures.

Author: V Narayanan

include/hash.h

@@ -63,7 +63,7 @@ void hash_replace(HASH *hash, HASH_SEARCH_STATE *state, byte *new_row);
 my_bool hash_check(HASH *hash);			/* Only in debug library */
 
 #define hash_clear(H) bzero((char*) (H),sizeof(*(H)))
-#define hash_inited(H) ((H)->array.buffer != 0)
+#define hash_inited(H) ((H)->blength != 0)
 #define hash_init_opt(A,B,C,D,E,F,G,H) \
           (!hash_inited(A) && _hash_init(A,B,C,D,E,F,G, H CALLER_INFO))
 

mysys/hash.c

@@ -45,6 +45,32 @@ static uint calc_hash(const HASH *hash, const byte *key, uint length)
   return nr1;
 }
 
+/**
+  @brief Initialize the hash
+  
+  @details
+
+  Initialize the hash, by defining and giving valid values for
+  its elements. The failure to allocate memory for the
+  hash->array element will not result in a fatal failure. The
+  dynamic array that is part of the hash will allocate memory
+  as required during insertion.
+
+  @param[in,out] hash         The hash that is initialized
+  @param[in]     charset      The charater set information
+  @param[in]     size         The hash size
+  @param[in]     key_offest   The key offset for the hash
+  @param[in]     key_length   The length of the key used in
+                              the hash
+  @param[in]     get_key      get the key for the hash
+  @param[in]     free_element pointer to the function that
+                              does cleanup
+  @param[in]     CALLER_INFO_PROTO flag that define the behaviour 
+                                   of the hash
+  @return        inidicates success or failure of initialization
+    @retval 0 success
+    @retval 1 failure
+*/
 my_bool
 _hash_init(HASH *hash,CHARSET_INFO *charset,
 	   uint size,uint key_offset,uint key_length,
@@ -55,19 +81,15 @@ _hash_init(HASH *hash,CHARSET_INFO *charset,
   DBUG_PRINT("enter",("hash: 0x%lx  size: %d", (long) hash, size));
 
   hash->records=0;
-  if (my_init_dynamic_array_ci(&hash->array,sizeof(HASH_LINK),size,0))
-  {
-    hash->free=0;				/* Allow call to hash_free */
-    DBUG_RETURN(1);
-  }
   hash->key_offset=key_offset;
   hash->key_length=key_length;
   hash->blength=1;
   hash->get_key=get_key;
   hash->free=free_element;
   hash->flags=flags;
   hash->charset=charset;
-  DBUG_RETURN(0);
+  DBUG_RETURN(my_init_dynamic_array_ci(&hash->array, 
+                                       sizeof(HASH_LINK), size, 0));
 }
 
 
@@ -113,6 +135,7 @@ void hash_free(HASH *hash)
   hash_free_elements(hash);
   hash->free= 0;
   delete_dynamic(&hash->array);
+  hash->blength= 0;
   DBUG_VOID_RETURN;
 }