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Overview
Comment:Strengthen the implementations of xShmMemoryBarrier on both the unix and windows VFSes, so that they likely work even if SQLITE_THREADSAFE=0 is used.
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SHA1:c6ab807b72ddfc1462f61aa91442b6fac04ace8a
User & Date: drh 2015-09-24 12:40:43
Context
2015-09-24
17:38
Fix over-length source code lines in where.c. No logic changes. check-in: 1c8c5380 user: drh tags: trunk
15:17
Merge all recent trunk enhancements and fixes into the begin-concurrent branch. check-in: c63c1e15 user: drh tags: begin-concurrent
15:06
Merge trunk changes into the cursor-hints branch. check-in: fbe63762 user: drh tags: cursor-hints
14:43
Merge recent trunk enhancements into the apple-osx branch. check-in: 4dd06d8b user: drh tags: apple-osx
14:26
Merge all the latest trunk enhancements into the sessions branch. check-in: c91065f8 user: drh tags: sessions
12:40
Strengthen the implementations of xShmMemoryBarrier on both the unix and windows VFSes, so that they likely work even if SQLITE_THREADSAFE=0 is used. check-in: c6ab807b user: drh tags: trunk
12:19
Make sure joins work correctly when both sides of the join are connected using indexed expressions. check-in: c2fcb032 user: drh tags: trunk
Changes
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Changes to src/os_unix.c.

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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);

  unixEnterMutex();
  unixLeaveMutex();
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**







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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void unixShmBarrier(
  sqlite3_file *fd                /* Database file holding the shared memory */
){
  UNUSED_PARAMETER(fd);
  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
  unixEnterMutex();               /* Also mutex, for redundancy */
  unixLeaveMutex();
}

/*
** Close a connection to shared-memory.  Delete the underlying 
** storage if deleteFlag is true.
**

Changes to src/os_win.c.

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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void winShmBarrier(
  sqlite3_file *fd          /* Database holding the shared memory */
){
  UNUSED_PARAMETER(fd);
  /* MemoryBarrier(); // does not work -- do not know why not */
  winShmEnterMutex();
  winShmLeaveMutex();
}

/*
** This function is called to obtain a pointer to region iRegion of the
** shared-memory associated with the database file fd. Shared-memory regions
** are numbered starting from zero. Each shared-memory region is szRegion







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** All loads and stores begun before the barrier must complete before
** any load or store begun after the barrier.
*/
static void winShmBarrier(
  sqlite3_file *fd          /* Database holding the shared memory */
){
  UNUSED_PARAMETER(fd);
  sqlite3MemoryBarrier();   /* compiler-defined memory barrier */
  winShmEnterMutex();       /* Also mutex, for redundancy */
  winShmLeaveMutex();
}

/*
** This function is called to obtain a pointer to region iRegion of the
** shared-memory associated with the database file fd. Shared-memory regions
** are numbered starting from zero. Each shared-memory region is szRegion