Convert the arithmetic for shared memory size calculation from 'int'

to 'Size' (that is, size_t), and install overflow detection checks in it.
This allows us to remove the former arbitrary restrictions on NBuffers
etc.  It won't make any difference in a 32-bit machine, but in a 64-bit
machine you could theoretically have terabytes of shared buffers.
(How efficiently we could manage 'em remains to be seen.)  Similarly,
num_temp_buffers, work_mem, and maintenance_work_mem can be set above
2Gb on a 64-bit machine.  Original patch from Koichi Suzuki, additional
work by moi.

src/backend/storage/ipc/ipci.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.77 2005/06/17 22:32:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.78 2005/08/20 23:26:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -61,36 +61,44 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 
 	if (!IsUnderPostmaster)
 	{
-		int			size;
+		Size		size;
 		int			numSemas;
 
 		/*
 		 * Size of the Postgres shared-memory block is estimated via
 		 * moderately-accurate estimates for the big hogs, plus 100K for
 		 * the stuff that's too small to bother with estimating.
+		 *
+		 * We take some care during this phase to ensure that the total
+		 * size request doesn't overflow size_t.  If this gets through,
+		 * we don't need to be so careful during the actual allocation
+		 * phase.
 		 */
-		size = hash_estimate_size(SHMEM_INDEX_SIZE, sizeof(ShmemIndexEnt));
-		size += BufferShmemSize();
-		size += LockShmemSize();
-		size += ProcGlobalShmemSize();
-		size += XLOGShmemSize();
-		size += CLOGShmemSize();
-		size += SUBTRANSShmemSize();
-		size += TwoPhaseShmemSize();
-		size += MultiXactShmemSize();
-		size += LWLockShmemSize();
-		size += ProcArrayShmemSize();
-		size += SInvalShmemSize(MaxBackends);
-		size += FreeSpaceShmemSize();
-		size += BgWriterShmemSize();
+		size = 100000;
+		size = add_size(size, hash_estimate_size(SHMEM_INDEX_SIZE,
+												 sizeof(ShmemIndexEnt)));
+		size = add_size(size, BufferShmemSize());
+		size = add_size(size, LockShmemSize());
+		size = add_size(size, ProcGlobalShmemSize());
+		size = add_size(size, XLOGShmemSize());
+		size = add_size(size, CLOGShmemSize());
+		size = add_size(size, SUBTRANSShmemSize());
+		size = add_size(size, TwoPhaseShmemSize());
+		size = add_size(size, MultiXactShmemSize());
+		size = add_size(size, LWLockShmemSize());
+		size = add_size(size, ProcArrayShmemSize());
+		size = add_size(size, SInvalShmemSize());
+		size = add_size(size, FreeSpaceShmemSize());
+		size = add_size(size, BgWriterShmemSize());
 #ifdef EXEC_BACKEND
-		size += ShmemBackendArraySize();
+		size = add_size(size, ShmemBackendArraySize());
 #endif
-		size += 100000;
-		/* might as well round it off to a multiple of a typical page size */
-		size += 8192 - (size % 8192);
 
-		elog(DEBUG3, "invoking IpcMemoryCreate(size=%d)", size);
+		/* might as well round it off to a multiple of a typical page size */
+		size = add_size(size, 8192 - (size % 8192));
+
+		elog(DEBUG3, "invoking IpcMemoryCreate(size=%lu)",
+			 (unsigned long) size);
 
 		/*
 		 * Create the shmem segment
@@ -163,7 +171,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 	/*
 	 * Set up shared-inval messaging
 	 */
-	CreateSharedInvalidationState(MaxBackends);
+	CreateSharedInvalidationState();
 
 	/*
 	 * Set up free-space map

src/backend/storage/ipc/pmsignal.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/pmsignal.c,v 1.18 2004/12/31 22:00:56 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/pmsignal.c,v 1.19 2005/08/20 23:26:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,7 +48,9 @@ PMSignalInit(void)
 	bool		found;
 
 	PMSignalFlags = (sig_atomic_t *)
-		ShmemInitStruct("PMSignalFlags", NUM_PMSIGNALS * sizeof(sig_atomic_t), &found);
+		ShmemInitStruct("PMSignalFlags",
+						NUM_PMSIGNALS * sizeof(sig_atomic_t),
+						&found);
 
 	if (!found)
 		MemSet(PMSignalFlags, 0, NUM_PMSIGNALS * sizeof(sig_atomic_t));

src/backend/storage/ipc/procarray.c

@@ -23,7 +23,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.5 2005/08/20 01:26:36 ishii Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.6 2005/08/20 23:26:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -81,11 +81,16 @@ static void DisplayXidCache(void);
 /*
  * Report shared-memory space needed by CreateSharedProcArray.
  */
-int
+Size
 ProcArrayShmemSize(void)
 {
-	return MAXALIGN(offsetof(ProcArrayStruct, procs) +
-					(MaxBackends + max_prepared_xacts) * sizeof(PGPROC *));
+	Size		size;
+
+	size = offsetof(ProcArrayStruct, procs);
+	size = add_size(size, mul_size(sizeof(PGPROC *),
+								   add_size(MaxBackends, max_prepared_xacts)));
+
+	return size;
 }
 
 /*

src/backend/storage/ipc/shmem.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/shmem.c,v 1.84 2005/05/29 04:23:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/shmem.c,v 1.85 2005/08/20 23:26:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -141,8 +141,8 @@ InitShmemAllocation(void *seghdr, bool init)
 void *
 ShmemAlloc(Size size)
 {
-	uint32		newStart;
-	uint32		newFree;
+	Size		newStart;
+	Size		newFree;
 	void	   *newSpace;
 
 	/* use volatile pointer to prevent code rearrangement */
@@ -415,3 +415,40 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 	SpinLockRelease(ShmemIndexLock);
 	return structPtr;
 }
+
+
+/*
+ * Add two Size values, checking for overflow
+ */
+Size
+add_size(Size s1, Size s2)
+{
+	Size		result;
+
+	result = s1 + s2;
+	/* We are assuming Size is an unsigned type here... */
+	if (result < s1 || result < s2)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("requested shared memory size overflows size_t")));
+	return result;
+}
+
+/*
+ * Multiply two Size values, checking for overflow
+ */
+Size
+mul_size(Size s1, Size s2)
+{
+	Size		result;
+
+	if (s1 == 0 || s2 == 0)
+		return 0;
+	result = s1 * s2;
+	/* We are assuming Size is an unsigned type here... */
+	if (result / s2 != s1)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("requested shared memory size overflows size_t")));
+	return result;
+}

src/backend/storage/ipc/sinval.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.76 2005/05/19 21:35:46 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.77 2005/08/20 23:26:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -55,10 +55,10 @@ static void ProcessCatchupEvent(void);
 /*	should be called only by the POSTMASTER									*/
 /****************************************************************************/
 void
-CreateSharedInvalidationState(int maxBackends)
+CreateSharedInvalidationState(void)
 {
 	/* SInvalLock must be initialized already, during LWLock init */
-	SIBufferInit(maxBackends);
+	SIBufferInit();
 }
 
 /*

src/backend/storage/ipc/sinvaladt.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.59 2005/05/19 21:35:46 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.60 2005/08/20 23:26:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,14 +32,15 @@ static void SISetProcStateInvalid(SISeg *segP);
 /*
  * SInvalShmemSize --- return shared-memory space needed
  */
-int
-SInvalShmemSize(int maxBackends)
+Size
+SInvalShmemSize(void)
 {
-	/*
-	 * Figure space needed. Note sizeof(SISeg) includes the first
-	 * ProcState entry.
-	 */
-	return sizeof(SISeg) + sizeof(ProcState) * (maxBackends - 1);
+	Size		size;
+
+	size = offsetof(SISeg, procState);
+	size = add_size(size, mul_size(sizeof(ProcState), MaxBackends));
+
+	return size;
 }
 
 /*
@@ -47,16 +48,15 @@ SInvalShmemSize(int maxBackends)
  *		Create and initialize a new SI message buffer
  */
 void
-SIBufferInit(int maxBackends)
+SIBufferInit(void)
 {
-	int			segSize;
 	SISeg	   *segP;
 	int			i;
 	bool		found;
 
 	/* Allocate space in shared memory */
-	segSize = SInvalShmemSize(maxBackends);
-	shmInvalBuffer = segP = (SISeg *) ShmemInitStruct("shmInvalBuffer", segSize, &found);
+	shmInvalBuffer = segP = (SISeg *)
+		ShmemInitStruct("shmInvalBuffer", SInvalShmemSize(), &found);
 	if (found)
 		return;
 
@@ -64,13 +64,13 @@ SIBufferInit(int maxBackends)
 	segP->minMsgNum = 0;
 	segP->maxMsgNum = 0;
 	segP->lastBackend = 0;
-	segP->maxBackends = maxBackends;
-	segP->freeBackends = maxBackends;
+	segP->maxBackends = MaxBackends;
+	segP->freeBackends = MaxBackends;
 
 	/* The buffer[] array is initially all unused, so we need not fill it */
 
 	/* Mark all backends inactive */
-	for (i = 0; i < maxBackends; i++)
+	for (i = 0; i < segP->maxBackends; i++)
 	{
 		segP->procState[i].nextMsgNum = -1;		/* inactive */
 		segP->procState[i].resetState = false;