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/buffer/buf_init.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.75 2005/08/12 05:05:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_init.c,v 1.76 2005/08/20 23:26:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -89,7 +89,7 @@ InitBufferPool(void)
 
 	BufferBlocks = (char *)
 		ShmemInitStruct("Buffer Blocks",
-						NBuffers * BLCKSZ, &foundBufs);
+						NBuffers * (Size) BLCKSZ, &foundBufs);
 
 	if (foundDescs || foundBufs)
 	{
@@ -155,8 +155,11 @@ InitBufferPoolAccess(void)
 	/*
 	 * Allocate and zero local arrays of per-buffer info.
 	 */
-	PrivateRefCount = (int32 *) calloc(NBuffers,
-									   sizeof(*PrivateRefCount));
+	PrivateRefCount = (int32 *) calloc(NBuffers, sizeof(int32));
+	if (!PrivateRefCount)
+		ereport(FATAL,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
 }
 
 /*
@@ -165,19 +168,19 @@ InitBufferPoolAccess(void)
  * compute the size of shared memory for the buffer pool including
  * data pages, buffer descriptors, hash tables, etc.
  */
-int
+Size
 BufferShmemSize(void)
 {
-	int			size = 0;
+	Size		size = 0;
 
 	/* size of buffer descriptors */
-	size += MAXALIGN(NBuffers * sizeof(BufferDesc));
+	size = add_size(size, mul_size(NBuffers, sizeof(BufferDesc)));
 
 	/* size of data pages */
-	size += NBuffers * MAXALIGN(BLCKSZ);
+	size = add_size(size, mul_size(NBuffers, BLCKSZ));
 
 	/* size of stuff controlled by freelist.c */
-	size += StrategyShmemSize();
+	size = add_size(size, StrategyShmemSize());
 
 	return size;
 }

src/backend/storage/buffer/buf_table.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.41 2005/05/29 04:23:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.42 2005/08/20 23:26:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,7 +37,7 @@ static HTAB *SharedBufHash;
  * Estimate space needed for mapping hashtable
  *		size is the desired hash table size (possibly more than NBuffers)
  */
-int
+Size
 BufTableShmemSize(int size)
 {
 	return hash_estimate_size(size, sizeof(BufferLookupEnt));

src/backend/storage/buffer/freelist.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.51 2005/03/04 20:21:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/freelist.c,v 1.52 2005/08/20 23:26:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -208,16 +208,16 @@ StrategyHintVacuum(bool vacuum_active)
  * Note: for somewhat historical reasons, the buffer lookup hashtable size
  * is also determined here.
  */
-int
+Size
 StrategyShmemSize(void)
 {
-	int			size = 0;
+	Size		size = 0;
 
 	/* size of lookup hash table */
-	size += BufTableShmemSize(NBuffers);
+	size = add_size(size, BufTableShmemSize(NBuffers));
 
 	/* size of the shared replacement strategy control block */
-	size += MAXALIGN(sizeof(BufferStrategyControl));
+	size = add_size(size, MAXALIGN(sizeof(BufferStrategyControl)));
 
 	return size;
 }

src/backend/storage/buffer/localbuf.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.68 2005/08/08 19:44:22 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.69 2005/08/20 23:26:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -255,15 +255,13 @@ InitLocalBuffers(void)
 	int			i;
 
 	/* Allocate and zero buffer headers and auxiliary arrays */
-	LocalBufferDescriptors = (BufferDesc *)
-		MemoryContextAllocZero(TopMemoryContext,
-							   nbufs * sizeof(BufferDesc));
-	LocalBufferBlockPointers = (Block *)
-		MemoryContextAllocZero(TopMemoryContext,
-							   nbufs * sizeof(Block));
-	LocalRefCount = (int32 *)
-		MemoryContextAllocZero(TopMemoryContext,
-							   nbufs * sizeof(int32));
+	LocalBufferDescriptors = (BufferDesc *) calloc(nbufs, sizeof(BufferDesc));
+	LocalBufferBlockPointers = (Block *) calloc(nbufs, sizeof(Block));
+	LocalRefCount = (int32 *) calloc(nbufs, sizeof(int32));
+	if (!LocalBufferDescriptors || !LocalBufferBlockPointers || !LocalRefCount)
+		ereport(FATAL,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("out of memory")));
 
 	nextFreeLocalBuf = 0;