Elaborate on the open-in-read-only fallback behavior of the SQLITE_OPEN_READWRITE flag, per user request. Unrelated trailing EOL whitespace cleanups.

FossilOrigin-Name: 1003144fc192e1531e1bc968d7e1d0ccc7ad31e501180f90e1479565a4abfb96

1 files changed, 66 insertions, 61 deletions

diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 213da4c79..53442d510 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -174,8 +174,8 @@ extern "C" {
 ** function is provided for use in DLLs since DLL users usually do not have
 ** direct access to string constants within the DLL.  ^The
 ** sqlite3_libversion_number() function returns an integer equal to
-** [SQLITE_VERSION_NUMBER].  ^(The sqlite3_sourceid() function returns 
-** a pointer to a string constant whose value is the same as the 
+** [SQLITE_VERSION_NUMBER].  ^(The sqlite3_sourceid() function returns
+** a pointer to a string constant whose value is the same as the
 ** [SQLITE_SOURCE_ID] C preprocessor macro.  Except if SQLite is built
 ** using an edited copy of [the amalgamation], then the last four characters
 ** of the hash might be different from [SQLITE_SOURCE_ID].)^
@@ -190,20 +190,20 @@ int sqlite3_libversion_number(void);
 /*
 ** CAPI3REF: Run-Time Library Compilation Options Diagnostics
 **
-** ^The sqlite3_compileoption_used() function returns 0 or 1 
-** indicating whether the specified option was defined at 
-** compile time.  ^The SQLITE_ prefix may be omitted from the 
-** option name passed to sqlite3_compileoption_used().  
+** ^The sqlite3_compileoption_used() function returns 0 or 1
+** indicating whether the specified option was defined at
+** compile time.  ^The SQLITE_ prefix may be omitted from the
+** option name passed to sqlite3_compileoption_used().
 **
 ** ^The sqlite3_compileoption_get() function allows iterating
 ** over the list of options that were defined at compile time by
 ** returning the N-th compile time option string.  ^If N is out of range,
-** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_ 
-** prefix is omitted from any strings returned by 
+** sqlite3_compileoption_get() returns a NULL pointer.  ^The SQLITE_
+** prefix is omitted from any strings returned by
 ** sqlite3_compileoption_get().
 **
 ** ^Support for the diagnostic functions sqlite3_compileoption_used()
-** and sqlite3_compileoption_get() may be omitted by specifying the 
+** and sqlite3_compileoption_get() may be omitted by specifying the
 ** [SQLITE_OMIT_COMPILEOPTION_DIAGS] option at compile time.
 **
 ** See also: SQL functions [sqlite_compileoption_used()] and
@@ -227,7 +227,7 @@ const char *sqlite3_compileoption_get(int N);
 ** SQLite can be compiled with or without mutexes.  When
 ** the [SQLITE_THREADSAFE] C preprocessor macro is 1 or 2, mutexes
 ** are enabled and SQLite is threadsafe.  When the
-** [SQLITE_THREADSAFE] macro is 0, 
+** [SQLITE_THREADSAFE] macro is 0,
 ** the mutexes are omitted.  Without the mutexes, it is not safe
 ** to use SQLite concurrently from more than one thread.
 **
@@ -284,14 +284,14 @@ typedef struct sqlite3 sqlite3;
 **
 ** ^The sqlite3_int64 and sqlite_int64 types can store integer values
 ** between -9223372036854775808 and +9223372036854775807 inclusive.  ^The
-** sqlite3_uint64 and sqlite_uint64 types can store integer values 
+** sqlite3_uint64 and sqlite_uint64 types can store integer values
 ** between 0 and +18446744073709551615 inclusive.
 */
 #ifdef SQLITE_INT64_TYPE
   typedef SQLITE_INT64_TYPE sqlite_int64;
 # ifdef SQLITE_UINT64_TYPE
     typedef SQLITE_UINT64_TYPE sqlite_uint64;
-# else  
+# else
     typedef unsigned SQLITE_INT64_TYPE sqlite_uint64;
 # endif
 #elif defined(_MSC_VER) || defined(__BORLANDC__)
@@ -323,7 +323,7 @@ typedef sqlite_uint64 sqlite3_uint64;
 ** resources are deallocated.
 **
 ** Ideally, applications should [sqlite3_finalize | finalize] all
-** [prepared statements], [sqlite3_blob_close | close] all [BLOB handles], and 
+** [prepared statements], [sqlite3_blob_close | close] all [BLOB handles], and
 ** [sqlite3_backup_finish | finish] all [sqlite3_backup] objects associated
 ** with the [sqlite3] object prior to attempting to close the object.
 ** ^If the database connection is associated with unfinalized prepared
@@ -367,7 +367,7 @@ typedef int (*sqlite3_callback)(void*,int,char**, char**);
 ** The sqlite3_exec() interface is a convenience wrapper around
 ** [sqlite3_prepare_v2()], [sqlite3_step()], and [sqlite3_finalize()],
 ** that allows an application to run multiple statements of SQL
-** without having to use a lot of C code. 
+** without having to use a lot of C code.
 **
 ** ^The sqlite3_exec() interface runs zero or more UTF-8 encoded,
 ** semicolon-separate SQL statements passed into its 2nd argument,
@@ -407,7 +407,7 @@ typedef int (*sqlite3_callback)(void*,int,char**, char**);
 ** from [sqlite3_column_name()].
 **
 ** ^If the 2nd parameter to sqlite3_exec() is a NULL pointer, a pointer
-** to an empty string, or a pointer that contains only whitespace and/or 
+** to an empty string, or a pointer that contains only whitespace and/or
 ** SQL comments, then no SQL statements are evaluated and the database
 ** is not changed.
 **
@@ -766,7 +766,7 @@ struct sqlite3_file {
 ** requested lock, then the call to xLock() is a no-op.
 ** xUnlock() downgrades the database file lock to either SHARED or NONE.
 *  If the lock is already at or below the requested lock state, then the call
-** to xUnlock() is a no-op. 
+** to xUnlock() is a no-op.
 ** The xCheckReservedLock() method checks whether any database connection,
 ** either in this process or in some other process, is holding a RESERVED,
 ** PENDING, or EXCLUSIVE lock on the file.  It returns true
@@ -894,7 +894,7 @@ struct sqlite3_io_methods {
 ** <li>[[SQLITE_FCNTL_CHUNK_SIZE]]
 ** The [SQLITE_FCNTL_CHUNK_SIZE] opcode is used to request that the VFS
 ** extends and truncates the database file in chunks of a size specified
-** by the user. The fourth argument to [sqlite3_file_control()] should 
+** by the user. The fourth argument to [sqlite3_file_control()] should
 ** point to an integer (type int) containing the new chunk-size to use
 ** for the nominated database. Allocating database file space in large
 ** chunks (say 1MB at a time), may reduce file-system fragmentation and
@@ -917,24 +917,24 @@ struct sqlite3_io_methods {
 ** <li>[[SQLITE_FCNTL_SYNC]]
 ** The [SQLITE_FCNTL_SYNC] opcode is generated internally by SQLite and
 ** sent to the VFS immediately before the xSync method is invoked on a
-** database file descriptor. Or, if the xSync method is not invoked 
-** because the user has configured SQLite with 
-** [PRAGMA synchronous | PRAGMA synchronous=OFF] it is invoked in place 
+** database file descriptor. Or, if the xSync method is not invoked
+** because the user has configured SQLite with
+** [PRAGMA synchronous | PRAGMA synchronous=OFF] it is invoked in place
 ** of the xSync method. In most cases, the pointer argument passed with
 ** this file-control is NULL. However, if the database file is being synced
 ** as part of a multi-database commit, the argument points to a nul-terminated
-** string containing the transactions super-journal file name. VFSes that 
-** do not need this signal should silently ignore this opcode. Applications 
-** should not call [sqlite3_file_control()] with this opcode as doing so may 
-** disrupt the operation of the specialized VFSes that do require it.  
+** string containing the transactions super-journal file name. VFSes that
+** do not need this signal should silently ignore this opcode. Applications
+** should not call [sqlite3_file_control()] with this opcode as doing so may
+** disrupt the operation of the specialized VFSes that do require it.
 **
 ** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
 ** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
 ** and sent to the VFS after a transaction has been committed immediately
 ** but before the database is unlocked. VFSes that do not need this signal
 ** should silently ignore this opcode. Applications should not call
-** [sqlite3_file_control()] with this opcode as doing so may disrupt the 
-** operation of the specialized VFSes that do require it.  
+** [sqlite3_file_control()] with this opcode as doing so may disrupt the
+** operation of the specialized VFSes that do require it.
 **
 ** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
 ** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
@@ -1007,7 +1007,7 @@ struct sqlite3_io_methods {
 ** upper-most shim only.
 **
 ** <li>[[SQLITE_FCNTL_PRAGMA]]
-** ^Whenever a [PRAGMA] statement is parsed, an [SQLITE_FCNTL_PRAGMA] 
+** ^Whenever a [PRAGMA] statement is parsed, an [SQLITE_FCNTL_PRAGMA]
 ** file control is sent to the open [sqlite3_file] object corresponding
 ** to the database file to which the pragma statement refers. ^The argument
 ** to the [SQLITE_FCNTL_PRAGMA] file control is an array of
@@ -1018,7 +1018,7 @@ struct sqlite3_io_methods {
 ** of the char** argument point to a string obtained from [sqlite3_mprintf()]
 ** or the equivalent and that string will become the result of the pragma or
 ** the error message if the pragma fails. ^If the
-** [SQLITE_FCNTL_PRAGMA] file control returns [SQLITE_NOTFOUND], then normal 
+** [SQLITE_FCNTL_PRAGMA] file control returns [SQLITE_NOTFOUND], then normal
 ** [PRAGMA] processing continues.  ^If the [SQLITE_FCNTL_PRAGMA]
 ** file control returns [SQLITE_OK], then the parser assumes that the
 ** VFS has handled the PRAGMA itself and the parser generates a no-op
@@ -1058,7 +1058,7 @@ struct sqlite3_io_methods {
 ** The argument is a pointer to a value of type sqlite3_int64 that
 ** is an advisory maximum number of bytes in the file to memory map.  The
 ** pointer is overwritten with the old value.  The limit is not changed if
-** the value originally pointed to is negative, and so the current limit 
+** the value originally pointed to is negative, and so the current limit
 ** can be queried by passing in a pointer to a negative number.  This
 ** file-control is used internally to implement [PRAGMA mmap_size].
 **
@@ -1102,7 +1102,7 @@ struct sqlite3_io_methods {
 ** <li>[[SQLITE_FCNTL_RBU]]
 ** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
 ** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
-** this opcode.  
+** this opcode.
 **
 ** <li>[[SQLITE_FCNTL_BEGIN_ATOMIC_WRITE]]
 ** If the [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] opcode returns SQLITE_OK, then
@@ -1119,7 +1119,7 @@ struct sqlite3_io_methods {
 **
 ** <li>[[SQLITE_FCNTL_COMMIT_ATOMIC_WRITE]]
 ** The [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE] opcode causes all write
-** operations since the previous successful call to 
+** operations since the previous successful call to
 ** [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] to be performed atomically.
 ** This file control returns [SQLITE_OK] if and only if the writes were
 ** all performed successfully and have been committed to persistent storage.
@@ -1131,7 +1131,7 @@ struct sqlite3_io_methods {
 **
 ** <li>[[SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE]]
 ** The [SQLITE_FCNTL_ROLLBACK_ATOMIC_WRITE] opcode causes all write
-** operations since the previous successful call to 
+** operations since the previous successful call to
 ** [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] to be rolled back.
 ** ^This file control takes the file descriptor out of batch write mode
 ** so that all subsequent write operations are independent.
@@ -1140,8 +1140,8 @@ struct sqlite3_io_methods {
 **
 ** <li>[[SQLITE_FCNTL_LOCK_TIMEOUT]]
 ** The [SQLITE_FCNTL_LOCK_TIMEOUT] opcode is used to configure a VFS
-** to block for up to M milliseconds before failing when attempting to 
-** obtain a file lock using the xLock or xShmLock methods of the VFS. 
+** to block for up to M milliseconds before failing when attempting to
+** obtain a file lock using the xLock or xShmLock methods of the VFS.
 ** The parameter is a pointer to a 32-bit signed integer that contains
 ** the value that M is to be set to. Before returning, the 32-bit signed
 ** integer is overwritten with the previous value of M.
@@ -1345,14 +1345,14 @@ typedef const char *sqlite3_filename;
 ** the [sqlite3_file] can safely store a pointer to the
 ** filename if it needs to remember the filename for some reason.
 ** If the zFilename parameter to xOpen is a NULL pointer then xOpen
-** must invent its own temporary name for the file.  ^Whenever the 
+** must invent its own temporary name for the file.  ^Whenever the
 ** xFilename parameter is NULL it will also be the case that the
 ** flags parameter will include [SQLITE_OPEN_DELETEONCLOSE].
 **
 ** The flags argument to xOpen() includes all bits set in
 ** the flags argument to [sqlite3_open_v2()].  Or if [sqlite3_open()]
 ** or [sqlite3_open16()] is used, then flags includes at least
-** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]. 
+** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE].
 ** If xOpen() opens a file read-only then it sets *pOutFlags to
 ** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be set.
 **
@@ -1394,10 +1394,10 @@ typedef const char *sqlite3_filename;
 ** ^The [SQLITE_OPEN_EXCLUSIVE] flag is always used in conjunction
 ** with the [SQLITE_OPEN_CREATE] flag, which are both directly
 ** analogous to the O_EXCL and O_CREAT flags of the POSIX open()
-** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the 
+** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the
 ** SQLITE_OPEN_CREATE, is used to indicate that file should always
 ** be created, and that it is an error if it already exists.
-** It is <i>not</i> used to indicate the file should be opened 
+** It is <i>not</i> used to indicate the file should be opened
 ** for exclusive access.
 **
 ** ^At least szOsFile bytes of memory are allocated by SQLite
@@ -1421,7 +1421,7 @@ typedef const char *sqlite3_filename;
 ** non-zero error code if there is an I/O error or if the name of
 ** the file given in the second argument is illegal.  If SQLITE_OK
 ** is returned, then non-zero or zero is written into *pResOut to indicate
-** whether or not the file is accessible.  
+** whether or not the file is accessible.
 **
 ** ^SQLite will always allocate at least mxPathname+1 bytes for the
 ** output buffer xFullPathname.  The exact size of the output buffer
@@ -1441,16 +1441,16 @@ typedef const char *sqlite3_filename;
 ** method returns a Julian Day Number for the current date and time as
 ** a floating point value.
 ** ^The xCurrentTimeInt64() method returns, as an integer, the Julian
-** Day Number multiplied by 86400000 (the number of milliseconds in 
-** a 24-hour day).  
+** Day Number multiplied by 86400000 (the number of milliseconds in
+** a 24-hour day).
 ** ^SQLite will use the xCurrentTimeInt64() method to get the current
-** date and time if that method is available (if iVersion is 2 or 
+** date and time if that method is available (if iVersion is 2 or
 ** greater and the function pointer is not NULL) and will fall back
 ** to xCurrentTime() if xCurrentTimeInt64() is unavailable.
 **
 ** ^The xSetSystemCall(), xGetSystemCall(), and xNestSystemCall() interfaces
 ** are not used by the SQLite core.  These optional interfaces are provided
-** by some VFSes to facilitate testing of the VFS code. By overriding 
+** by some VFSes to facilitate testing of the VFS code. By overriding
 ** system calls with functions under its control, a test program can
 ** simulate faults and error conditions that would otherwise be difficult
 ** or impossible to induce.  The set of system calls that can be overridden
@@ -1541,7 +1541,7 @@ struct sqlite3_vfs {
 ** </ul>
 **
 ** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
-** was given on the corresponding lock.  
+** was given on the corresponding lock.
 **
 ** The xShmLock method can transition between unlocked and SHARED or
 ** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
@@ -1704,7 +1704,7 @@ int sqlite3_db_config(sqlite3*, int op, ...);
 ** This object is used in only one place in the SQLite interface.
 ** A pointer to an instance of this object is the argument to
 ** [sqlite3_config()] when the configuration option is
-** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].  
+** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].
 ** By creating an instance of this object
 ** and passing it to [sqlite3_config]([SQLITE_CONFIG_MALLOC])
 ** during configuration, an application can specify an alternative
@@ -1827,7 +1827,7 @@ struct sqlite3_mem_methods {
 ** SQLITE_CONFIG_SERIALIZED configuration option.</dd>
 **
 ** [[SQLITE_CONFIG_MALLOC]] <dt>SQLITE_CONFIG_MALLOC</dt>
-** <dd> ^(The SQLITE_CONFIG_MALLOC option takes a single argument which is 
+** <dd> ^(The SQLITE_CONFIG_MALLOC option takes a single argument which is
 ** a pointer to an instance of the [sqlite3_mem_methods] structure.
 ** The argument specifies
 ** alternative low-level memory allocation routines to be used in place of
@@ -1878,7 +1878,7 @@ struct sqlite3_mem_methods {
 ** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
 ** <dd> ^The SQLITE_CONFIG_PAGECACHE option specifies a memory pool
 ** that SQLite can use for the database page cache with the default page
-** cache implementation.  
+** cache implementation.
 ** This configuration option is a no-op if an application-defined page
 ** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2].
 ** ^There are three arguments to SQLITE_CONFIG_PAGECACHE: A pointer to
@@ -1906,7 +1906,7 @@ struct sqlite3_mem_methods {
 ** additional cache line. </dd>
 **
 ** [[SQLITE_CONFIG_HEAP]] <dt>SQLITE_CONFIG_HEAP</dt>
-** <dd> ^The SQLITE_CONFIG_HEAP option specifies a static memory buffer 
+** <dd> ^The SQLITE_CONFIG_HEAP option specifies a static memory buffer
 ** that SQLite will use for all of its dynamic memory allocation needs
 ** beyond those provided for by [SQLITE_CONFIG_PAGECACHE].
 ** ^The SQLITE_CONFIG_HEAP option is only available if SQLite is compiled
@@ -1961,7 +1961,7 @@ struct sqlite3_mem_methods {
 ** configuration on individual connections.)^ </dd>
 **
 ** [[SQLITE_CONFIG_PCACHE2]] <dt>SQLITE_CONFIG_PCACHE2</dt>
-** <dd> ^(The SQLITE_CONFIG_PCACHE2 option takes a single argument which is 
+** <dd> ^(The SQLITE_CONFIG_PCACHE2 option takes a single argument which is
 ** a pointer to an [sqlite3_pcache_methods2] object.  This object specifies
 ** the interface to a custom page cache implementation.)^
 ** ^SQLite makes a copy of the [sqlite3_pcache_methods2] object.</dd>
@@ -1975,7 +1975,7 @@ struct sqlite3_mem_methods {
 ** <dd> The SQLITE_CONFIG_LOG option is used to configure the SQLite
 ** global [error log].
 ** (^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
-** function with a call signature of void(*)(void*,int,const char*), 
+** function with a call signature of void(*)(void*,int,const char*),
 ** and a pointer to void. ^If the function pointer is not NULL, it is
 ** invoked by [sqlite3_log()] to process each logging event.  ^If the
 ** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
@@ -2084,7 +2084,7 @@ struct sqlite3_mem_methods {
 ** [[SQLITE_CONFIG_STMTJRNL_SPILL]]
 ** <dt>SQLITE_CONFIG_STMTJRNL_SPILL
 ** <dd>^The SQLITE_CONFIG_STMTJRNL_SPILL option takes a single parameter which
-** becomes the [statement journal] spill-to-disk threshold.  
+** becomes the [statement journal] spill-to-disk threshold.
 ** [Statement journals] are held in memory until their size (in bytes)
 ** exceeds this threshold, at which point they are written to disk.
 ** Or if the threshold is -1, statement journals are always held
@@ -2106,7 +2106,7 @@ struct sqlite3_mem_methods {
 ** than the configured sorter-reference size threshold - then a reference
 ** is stored in each sorted record and the required column values loaded
 ** from the database as records are returned in sorted order. The default
-** value for this option is to never use this optimization. Specifying a 
+** value for this option is to never use this optimization. Specifying a
 ** negative value for this option restores the default behaviour.
 ** This option is only available if SQLite is compiled with the
 ** [SQLITE_ENABLE_SORTER_REFERENCES] compile-time option.
@@ -2134,7 +2134,7 @@ struct sqlite3_mem_methods {
 #define SQLITE_CONFIG_MEMSTATUS     9  /* boolean */
 #define SQLITE_CONFIG_MUTEX        10  /* sqlite3_mutex_methods* */
 #define SQLITE_CONFIG_GETMUTEX     11  /* sqlite3_mutex_methods* */
-/* previously SQLITE_CONFIG_CHUNKALLOC 12 which is now unused. */ 
+/* previously SQLITE_CONFIG_CHUNKALLOC 12 which is now unused. */
 #define SQLITE_CONFIG_LOOKASIDE    13  /* int int */
 #define SQLITE_CONFIG_PCACHE       14  /* no-op */
 #define SQLITE_CONFIG_GETPCACHE    15  /* no-op */
@@ -2169,7 +2169,7 @@ struct sqlite3_mem_methods {
 ** <dl>
 ** [[SQLITE_DBCONFIG_LOOKASIDE]]
 ** <dt>SQLITE_DBCONFIG_LOOKASIDE</dt>
-** <dd> ^This option takes three additional arguments that determine the 
+** <dd> ^This option takes three additional arguments that determine the
 ** [lookaside memory allocator] configuration for the [database connection].
 ** ^The first argument (the third parameter to [sqlite3_db_config()] is a
 ** pointer to a memory buffer to use for lookaside memory.
@@ -2187,7 +2187,7 @@ struct sqlite3_mem_methods {
 ** when the "current value" returned by
 ** [sqlite3_db_status](D,[SQLITE_DBSTATUS_LOOKASIDE_USED],...) is zero.
 ** Any attempt to change the lookaside memory configuration when lookaside
-** memory is in use leaves the configuration unchanged and returns 
+** memory is in use leaves the configuration unchanged and returns
 ** [SQLITE_BUSY].)^</dd>
 **
 ** [[SQLITE_DBCONFIG_ENABLE_FKEY]]
@@ -3394,7 +3394,7 @@ void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);
 ** CAPI3REF: Opening A New Database Connection
 ** CONSTRUCTOR: sqlite3
 **
-** ^These routines open an SQLite database file as specified by the 
+** ^These routines open an SQLite database file as specified by the
 ** filename argument. ^The filename argument is interpreted as UTF-8 for
 ** sqlite3_open() and sqlite3_open_v2() and as UTF-16 in the native byte
 ** order for sqlite3_open16(). ^(A [database connection] handle is usually
@@ -3423,13 +3423,18 @@ void sqlite3_progress_handler(sqlite3*, int, int(*)(void*), void*);
 **
 ** <dl>
 ** ^(<dt>[SQLITE_OPEN_READONLY]</dt>
-** <dd>The database is opened in read-only mode.  If the database does not
-** already exist, an error is returned.</dd>)^
+** <dd>The database is opened in read-only mode.  If the database does
+** not already exist, an error is returned.</dd>)^
 **
 ** ^(<dt>[SQLITE_OPEN_READWRITE]</dt>
-** <dd>The database is opened for reading and writing if possible, or reading
-** only if the file is write protected by the operating system.  In either
-** case the database must already exist, otherwise an error is returned.</dd>)^
+** <dd>The database is opened for reading and writing if possible, or
+** reading only if the file is write protected by the operating
+** system.  In either case the database must already exist, otherwise
+** an error is returned.  For historical reasons, if opening in
+** read-write mode fails due to OS-level permissions, an attempt is
+** made to open it in read-only mode. [sqlite3_db_readonly()] can be
+** used to determine whether the database is actually
+** read-write.</dd>)^
 **
 ** ^(<dt>[SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]</dt>
 ** <dd>The database is opened for reading and writing, and is created if