1 files changed, 22 insertions, 27 deletions

diff --git a/src/mem5.c b/src/mem5.c
index 783cef6..67615bb 100644
--- a/src/mem5.c
+++ b/src/mem5.c
@@ -130,13 +130,13 @@ static SQLITE_WSD struct Mem5Global {
 } mem5;
 
 /*
-** Access the static variable through a macro for SQLITE_OMIT_WSD
+** Access the static variable through a macro for SQLITE_OMIT_WSD.
 */
 #define mem5 GLOBAL(struct Mem5Global, mem5)
 
 /*
 ** Assuming mem5.zPool is divided up into an array of Mem5Link
-** structures, return a pointer to the idx-th such lik.
+** structures, return a pointer to the idx-th such link.
 */
 #define MEM5LINK(idx) ((Mem5Link *)(&mem5.zPool[(idx)*mem5.szAtom]))
 
@@ -202,7 +202,7 @@ static void memsys5Leave(void){
 static int memsys5Size(void *p){
   int iSize = 0;
   if( p ){
-    int i = ((u8 *)p-mem5.zPool)/mem5.szAtom;
+    int i = (int)(((u8 *)p-mem5.zPool)/mem5.szAtom);
     assert( i>=0 && i<mem5.nBlock );
     iSize = mem5.szAtom * (1 << (mem5.aCtrl[i]&CTRL_LOGSIZE));
   }
@@ -210,29 +210,10 @@ static int memsys5Size(void *p){
 }
 
 /*
-** Find the first entry on the freelist iLogsize.  Unlink that
-** entry and return its index. 
-*/
-static int memsys5UnlinkFirst(int iLogsize){
-  int i;
-  int iFirst;
-
-  assert( iLogsize>=0 && iLogsize<=LOGMAX );
-  i = iFirst = mem5.aiFreelist[iLogsize];
-  assert( iFirst>=0 );
-  while( i>0 ){
-    if( i<iFirst ) iFirst = i;
-    i = MEM5LINK(i)->next;
-  }
-  memsys5Unlink(iFirst, iLogsize);
-  return iFirst;
-}
-
-/*
 ** Return a block of memory of at least nBytes in size.
 ** Return NULL if unable.  Return NULL if nBytes==0.
 **
-** The caller guarantees that nByte positive.
+** The caller guarantees that nByte is positive.
 **
 ** The caller has obtained a mutex prior to invoking this
 ** routine so there is never any chance that two or more
@@ -267,13 +248,14 @@ static void *memsys5MallocUnsafe(int nByte){
   ** block.  If not, then split a block of the next larger power of
   ** two in order to create a new free block of size iLogsize.
   */
-  for(iBin=iLogsize; mem5.aiFreelist[iBin]<0 && iBin<=LOGMAX; iBin++){}
+  for(iBin=iLogsize; iBin<=LOGMAX && mem5.aiFreelist[iBin]<0; iBin++){}
   if( iBin>LOGMAX ){
     testcase( sqlite3GlobalConfig.xLog!=0 );
     sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes", nByte);
     return 0;
   }
-  i = memsys5UnlinkFirst(iBin);
+  i = mem5.aiFreelist[iBin];
+  memsys5Unlink(i, iBin);
   while( iBin>iLogsize ){
     int newSize;
 
@@ -293,6 +275,12 @@ static void *memsys5MallocUnsafe(int nByte){
   if( mem5.maxCount<mem5.currentCount ) mem5.maxCount = mem5.currentCount;
   if( mem5.maxOut<mem5.currentOut ) mem5.maxOut = mem5.currentOut;
 
+#ifdef SQLITE_DEBUG
+  /* Make sure the allocated memory does not assume that it is set to zero
+  ** or retains a value from a previous allocation */
+  memset(&mem5.zPool[i*mem5.szAtom], 0xAA, iFullSz);
+#endif
+
   /* Return a pointer to the allocated memory. */
   return (void*)&mem5.zPool[i*mem5.szAtom];
 }
@@ -307,7 +295,7 @@ static void memsys5FreeUnsafe(void *pOld){
   /* Set iBlock to the index of the block pointed to by pOld in 
   ** the array of mem5.szAtom byte blocks pointed to by mem5.zPool.
   */
-  iBlock = ((u8 *)pOld-mem5.zPool)/mem5.szAtom;
+  iBlock = (int)(((u8 *)pOld-mem5.zPool)/mem5.szAtom);
 
   /* Check that the pointer pOld points to a valid, non-free block. */
   assert( iBlock>=0 && iBlock<mem5.nBlock );
@@ -350,11 +338,18 @@ static void memsys5FreeUnsafe(void *pOld){
     }
     size *= 2;
   }
+
+#ifdef SQLITE_DEBUG
+  /* Overwrite freed memory with the 0x55 bit pattern to verify that it is
+  ** not used after being freed */
+  memset(&mem5.zPool[iBlock*mem5.szAtom], 0x55, size);
+#endif
+
   memsys5Link(iBlock, iLogsize);
 }
 
 /*
-** Allocate nBytes of memory
+** Allocate nBytes of memory.
 */
 static void *memsys5Malloc(int nBytes){
   sqlite3_int64 *p = 0;