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/*-
* Copyright (c) 2014-present MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
/*
* NOTE: If you see a compile failure in this file, your compiler is laying out structs in memory in
* a way WiredTiger does not expect. Please refer to the build instructions in the documentation
* (docs/html/install.html) for more information.
*/
/*
* Compile time assertions.
*
* If the argument to WT_STATIC_ASSERT is zero, the macro evaluates to:
*
* (void)sizeof(char[-1])
*
* which fails to compile (which is what we want, the assertion failed).
* If the value of the argument to WT_STATIC_ASSERT is non-zero, then the
* macro evaluates to:
*
* (void)sizeof(char[1]);
*
* which compiles with no warnings, and produces no code.
*
* For more details about why this works, see
* http://scaryreasoner.wordpress.com/2009/02/28/
*/
#define WT_STATIC_ASSERT(cond) (void)sizeof(char[1 - 2 * !(cond)])
#define WT_SIZE_CHECK(type, e) \
do { \
char __check_##type[1 - 2 * !(sizeof(type) == (e))]; \
(void)__check_##type; \
} while (0)
#define WT_ALIGN_CHECK(type, a) WT_STATIC_ASSERT(WT_ALIGN(sizeof(type), (a)) == sizeof(type))
/*
* __wt_verify_build --
* This function is never called: it exists so there is a place for code that checks build-time
* conditions.
*/
static inline void
__wt_verify_build(void)
{
/* Check specific structures weren't padded. */
WT_SIZE_CHECK(WT_BLOCK_DESC, WT_BLOCK_DESC_SIZE);
WT_SIZE_CHECK(WT_REF, WT_REF_SIZE);
/*
* WT_UPDATE is special: we arrange fields to avoid padding within the structure but it could be
* padded at the end depending on the timestamp size. Further check that the data field in the
* update structure is where we expect it.
*/
WT_SIZE_CHECK(WT_UPDATE, WT_ALIGN(WT_UPDATE_SIZE, 8));
WT_STATIC_ASSERT(offsetof(WT_UPDATE, data) == WT_UPDATE_SIZE);
/* Check specific structures were padded. */
#define WT_PADDING_CHECK(s) \
WT_STATIC_ASSERT( \
sizeof(s) > WT_CACHE_LINE_ALIGNMENT || sizeof(s) % WT_CACHE_LINE_ALIGNMENT == 0)
WT_PADDING_CHECK(WT_LOGSLOT);
WT_PADDING_CHECK(WT_TXN_SHARED);
/*
* The btree code encodes key/value pairs in size_t's, and requires at least 8B size_t's.
*/
WT_STATIC_ASSERT(sizeof(size_t) >= 8);
/*
* We require a wt_off_t fit into an 8B chunk because 8B is the largest integral value we can
* encode into an address cookie.
*
* WiredTiger has never been tested on a system with 4B file offsets, disallow them for now.
*/
WT_STATIC_ASSERT(sizeof(wt_off_t) == 8);
/*
* We require a time_t be an integral type and fit into a uint64_t for simplicity.
*/
WT_STATIC_ASSERT(sizeof(time_t) <= sizeof(uint64_t));
}
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