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.

1 files changed, 40 insertions, 3 deletions

diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index 9af059139e7..76b3ef26cc4 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/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;
+}