The sqlite3_memory_alarm() interface has been deprecated and undocumented

for almost 8 years (since version 3.5.3).  Change it into a no-op.

FossilOrigin-Name: 5d3f5df4da9f40d5897b5c23b2ea9333fc18ac2c

1 files changed, 53 insertions, 82 deletions

diff --git a/src/malloc.c b/src/malloc.c
index f402728e7..23d7598ae 100644
--- a/src/malloc.c
+++ b/src/malloc.c
@@ -45,16 +45,7 @@ typedef struct ScratchFreeslot {
 */
 static SQLITE_WSD struct Mem0Global {
   sqlite3_mutex *mutex;         /* Mutex to serialize access */
-
-  /*
-  ** The alarm callback and its arguments.  The mem0.mutex lock will
-  ** be held while the callback is running.  Recursive calls into
-  ** the memory subsystem are allowed, but no new callbacks will be
-  ** issued.
-  */
-  sqlite3_int64 alarmThreshold;
-  void (*alarmCallback)(void*, sqlite3_int64,int);
-  void *alarmArg;
+  sqlite3_int64 alarmThreshold;  /* The soft heap limit */
 
   /*
   ** Pointers to the end of sqlite3GlobalConfig.pScratch memory
@@ -71,7 +62,7 @@ static SQLITE_WSD struct Mem0Global {
   ** sqlite3_soft_heap_limit() setting.
   */
   int nearlyFull;
-} mem0 = { 0, 0, 0, 0, 0, 0, 0, 0 };
+} mem0 = { 0, 0, 0, 0, 0, 0 };
 
 #define mem0 GLOBAL(struct Mem0Global, mem0)
 
@@ -83,49 +74,59 @@ sqlite3_mutex *sqlite3MallocMutex(void){
 }
 
 /*
-** This routine runs when the memory allocator sees that the
-** total memory allocation is about to exceed the soft heap
-** limit.
+** Return the amount of memory currently in use.
 */
-static void softHeapLimitEnforcer(
-  void *NotUsed, 
-  sqlite3_int64 NotUsed2,
-  int allocSize
-){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  sqlite3_release_memory(allocSize);
+static sqlite3_int64 memInUse(void){
+  assert( sqlite3_mutex_held(mem0.mutex) );
+  return sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
 }
 
 /*
-** Change the alarm callback
+** Called when the soft heap limit is exceeded for an allocation
+** of nBytes.
 */
-static int sqlite3MemoryAlarm(
-  void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
-  void *pArg,
-  sqlite3_int64 iThreshold
-){
-  sqlite3_int64 nUsed;
-  sqlite3_mutex_enter(mem0.mutex);
-  mem0.alarmCallback = xCallback;
-  mem0.alarmArg = pArg;
-  mem0.alarmThreshold = iThreshold;
-  nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
-  mem0.nearlyFull = (iThreshold>0 && iThreshold<=nUsed);
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+static void sqlite3HeapLimitExceeded(int nByte){
+  sqlite3_int64 excess = memInUse() + nByte - mem0.alarmThreshold;
   sqlite3_mutex_leave(mem0.mutex);
-  return SQLITE_OK;
+  sqlite3_release_memory((int)(excess & 0x7fffffff));
+  sqlite3_mutex_enter(mem0.mutex);
+}
+#else
+# define sqlite3HeapLimitExceeded(X)  /* no-op */
+#endif
+
+/*
+** Check to see if increasing the total memory usage by nNew bytes
+** will exceed the soft heap limit.  
+**
+** If the soft heap limit is exceeded, set the mem0.nearlyFull flag
+** and invoke sqlite3HeapLimitExceeded() to try to free up some
+** memory.
+*/
+static void sqlite3CheckSoftHeapLimit(int nNew){
+  assert( sqlite3_mutex_held(mem0.mutex) );
+  if( mem0.alarmThreshold>0 ){
+    if( mem0.alarmThreshold-nNew >= memInUse() ){
+      mem0.nearlyFull = 1;
+      sqlite3HeapLimitExceeded(nNew);
+    }else{
+      mem0.nearlyFull = 0;
+    }
+  }
 }
 
 #ifndef SQLITE_OMIT_DEPRECATED
 /*
-** Deprecated external interface.  Internal/core SQLite code
-** should call sqlite3MemoryAlarm.
+** Deprecated external interface.  First deprecated 2007-11-05.  Changed
+** into a no-op on 2015-09-02.
 */
 int sqlite3_memory_alarm(
   void(*xCallback)(void *pArg, sqlite3_int64 used,int N),
   void *pArg,
   sqlite3_int64 iThreshold
 ){
-  return sqlite3MemoryAlarm(xCallback, pArg, iThreshold);
+  return SQLITE_OK;
 }
 #endif
 
@@ -135,22 +136,20 @@ int sqlite3_memory_alarm(
 */
 sqlite3_int64 sqlite3_soft_heap_limit64(sqlite3_int64 n){
   sqlite3_int64 priorLimit;
-  sqlite3_int64 excess;
 #ifndef SQLITE_OMIT_AUTOINIT
   int rc = sqlite3_initialize();
   if( rc ) return -1;
 #endif
   sqlite3_mutex_enter(mem0.mutex);
   priorLimit = mem0.alarmThreshold;
-  sqlite3_mutex_leave(mem0.mutex);
-  if( n<0 ) return priorLimit;
   if( n>0 ){
-    sqlite3MemoryAlarm(softHeapLimitEnforcer, 0, n);
-  }else{
-    sqlite3MemoryAlarm(0, 0, 0);
+    mem0.alarmThreshold = n;
+    sqlite3CheckSoftHeapLimit(0);
+  }else if( n==0 ){
+    mem0.alarmThreshold = 0;
+    mem0.nearlyFull = 0;
   }
-  excess = sqlite3_memory_used() - n;
-  if( excess>0 ) sqlite3_release_memory((int)(excess & 0x7fffffff));
+  sqlite3_mutex_leave(mem0.mutex);
   return priorLimit;
 }
 void sqlite3_soft_heap_limit(int n){
@@ -242,25 +241,6 @@ sqlite3_int64 sqlite3_memory_highwater(int resetFlag){
 }
 
 /*
-** Trigger the alarm 
-*/
-static void sqlite3MallocAlarm(int nByte){
-  void (*xCallback)(void*,sqlite3_int64,int);
-  sqlite3_int64 nowUsed;
-  void *pArg;
-  if( mem0.alarmCallback==0 ) return;
-  xCallback = mem0.alarmCallback;
-  nowUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
-  pArg = mem0.alarmArg;
-  mem0.alarmCallback = 0;
-  sqlite3_mutex_leave(mem0.mutex);
-  xCallback(pArg, nowUsed, nByte);
-  sqlite3_mutex_enter(mem0.mutex);
-  mem0.alarmCallback = xCallback;
-  mem0.alarmArg = pArg;
-}
-
-/*
 ** Do a memory allocation with statistics and alarms.  Assume the
 ** lock is already held.
 */
@@ -270,19 +250,11 @@ static int mallocWithAlarm(int n, void **pp){
   assert( sqlite3_mutex_held(mem0.mutex) );
   nFull = sqlite3GlobalConfig.m.xRoundup(n);
   sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, n);
-  if( mem0.alarmCallback!=0 ){
-    sqlite3_int64 nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
-    if( nUsed >= mem0.alarmThreshold - nFull ){
-      mem0.nearlyFull = 1;
-      sqlite3MallocAlarm(nFull);
-    }else{
-      mem0.nearlyFull = 0;
-    }
-  }
+  sqlite3CheckSoftHeapLimit(nFull);
   p = sqlite3GlobalConfig.m.xMalloc(nFull);
 #ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-  if( p==0 && mem0.alarmCallback ){
-    sqlite3MallocAlarm(nFull);
+  if( p==0 && mem0.alarmThreshold ){
+    sqlite3HeapLimitExceeded(nFull);
     p = sqlite3GlobalConfig.m.xMalloc(nFull);
   }
 #endif
@@ -565,15 +537,14 @@ void *sqlite3Realloc(void *pOld, u64 nBytes){
     sqlite3_mutex_enter(mem0.mutex);
     sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, (int)nBytes);
     nDiff = nNew - nOld;
-    if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED) >= 
-          mem0.alarmThreshold-nDiff ){
-      sqlite3MallocAlarm(nDiff);
-    }
+    sqlite3CheckSoftHeapLimit(nDiff);
     pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
-    if( pNew==0 && mem0.alarmCallback ){
-      sqlite3MallocAlarm((int)nBytes);
+#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
+    if( pNew==0 && mem0.alarmThreshold ){
+      sqlite3HeapLimitExceeded((int)nBytes);
       pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
     }
+#endif
     if( pNew ){
       nNew = sqlite3MallocSize(pNew);
       sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nNew-nOld);