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Avoid too-large shift on 32-bit Windows.

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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.
This commit is contained in:
Robert Haas 2013-10-30 09:13:42 -04:00
parent 6756c8ad30
commit 343bb134ea
1 changed files with 11 additions and 2 deletions
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13
src/backend/storage/ipc/dsm_impl.c
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@ -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. */ /* Create new segment or open an existing one for attach. */
if (op == DSM_OP_CREATE) if (op == DSM_OP_CREATE)
{ {
DWORD size_high = (DWORD) (request_size >> 32); DWORD size_high;
DWORD size_low = (DWORD) request_size; 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 */ hmap = CreateFileMapping(INVALID_HANDLE_VALUE, /* Use the pagefile */
NULL, /* Default security attrs */ NULL, /* Default security attrs */
PAGE_READWRITE, /* Memory is read/write */ PAGE_READWRITE, /* Memory is read/write */