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Improve the comment on walIndexPage() to more accurately describe the

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post-conditions.

FossilOrigin-Name: b619e936455f4001b543a9a58dea2ac9ebd598327d6be01130ca6e7e9764ffe6
This commit is contained in:
drh
2021-10-27 19:57:59 +00:00
parent 9b2adcc3d1
commit 5f25627a1c
3 changed files with 20 additions and 11 deletions
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14
src/wal.c
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@@ -620,9 +620,13 @@ struct WalIterator {
** so. It is safe to enlarge the wal-index if pWal->writeLock is true
** or pWal->exclusiveMode==WAL_HEAPMEMORY_MODE.
**
** If this call is successful, *ppPage is set to point to the wal-index
** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
** then an SQLite error code is returned and *ppPage is set to 0.
** Three possible result scenarios:
**
** (1) rc==SQLITE_OK and *ppPage==Requested-Wal-Index-Page
** (2) rc>=SQLITE_ERROR and *ppPage==NULL
** (3) rc==SQLITE_OK and *ppPage==NULL // only if iPage==0
**
** Scenario (3) can only occur when pWal->writeLock is false and iPage==0
*/
static SQLITE_NOINLINE int walIndexPageRealloc(
Wal *pWal, /* The WAL context */
@@ -655,7 +659,9 @@ static SQLITE_NOINLINE int walIndexPageRealloc(
rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ,
pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
);
assert( pWal->apWiData[iPage]!=0 || rc!=SQLITE_OK || pWal->writeLock==0 );
assert( pWal->apWiData[iPage]!=0
|| rc!=SQLITE_OK
|| (pWal->writeLock==0 && iPage==0) );
testcase( pWal->apWiData[iPage]==0 && rc==SQLITE_OK );
if( rc==SQLITE_OK ){
if( iPage>0 && sqlite3FaultSim(600) ) rc = SQLITE_NOMEM;