From 343bb134ea20d3b7286c620c15a067da79cab724 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 30 Oct 2013 09:13:42 -0400
Subject: [PATCH] Avoid too-large shift on 32-bit Windows.
Apparently, shifts greater than or equal to the width of the type
are undefined, and can surprisingly produce a non-zero value.
Amit Kapila, with a comment by me.
---
src/backend/storage/ipc/dsm_impl.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index 2056668ae99..811ac0437ce 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -673,8 +673,17 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size,
/* Create new segment or open an existing one for attach. */
if (op == DSM_OP_CREATE)
{
- DWORD size_high = (DWORD) (request_size >> 32);
- DWORD size_low = (DWORD) request_size;
+ DWORD size_high;
+ DWORD size_low;
+
+ /* Shifts >= the width of the type are undefined. */
+#ifdef _WIN64
+ size_high = request_size >> 32;
+#else
+ size_high = 0;
+#endif
+ size_low = (DWORD) request_size;
+
hmap = CreateFileMapping(INVALID_HANDLE_VALUE, /* Use the pagefile */
NULL, /* Default security attrs */
PAGE_READWRITE, /* Memory is read/write */
--
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