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<title>Compile-time Options</title>
<tcl>hd_keywords {compile-time options}</tcl>

<table_of_contents>

<h1>Overview</h1>

<p>
For most purposes, SQLite can be built just fine using the default
compilation options. However, if required, the compile-time options
documented below can be used to 
<a href="#omitfeatures">omit SQLite features</a> (resulting in
a [relfootprint | smaller compiled library size]) or to change the
<a href="#defaults">default values</a> of some parameters.
</p>

<p>
Every effort has been made to ensure that the various combinations
of compilation options work harmoniously and produce a working library.
Nevertheless, it is strongly recommended that the SQLite test-suite
be executed to check for errors before using an SQLite library built
with non-standard compilation options.
</p>

<tcl>
proc COMPILE_OPTION {name text} {
  if {[regexp {(SQLITE|HAVE)_([A-Z0-9_]+)} $name all prefix label]} {
    hd_fragment [string tolower $label]
    hd_keywords $all -D$all
  }
  if {[regexp {^YY([A-Z0-9_]+)} $name all label]} {
    hd_fragment [string tolower $all]
    hd_keywords $all
  }
  hd_puts <p><b>$name</b></p>
  regsub -all "\n\\s*\n" $text "</p>\n\n<p>" text
  hd_resolve <blockquote><p>$text</p></blockquote>
}

hd_fragment rcmd {recommended compile-time options}
</tcl>

<h1>Recommended Compile-time Options</h1>

<p>The following compile-time options are recommended for applications that
are able to use them, in order to minimized the number of CPU cycles and
the bytes of memory used by SQLite.
Not all of these compile-time options are usable by every application.
For example, the SQLITE_THREADSAFE=0 option is only usable by applications
that never access SQLite from more than one thread at a time.  And the
SQLITE_OMIT_PROGRESS_CALLBACK option is only usable by applications that
doe not use the [sqlite3_progress_handler()] interface.  And so forth.

<p>It is impossible to test every possible combination of compile-time
options for SQLite.  But the following set of compile-time options is
one configuration that is always fully tested.

<ol>
<li><p><b>[SQLITE_THREADSAFE=0]</b>.
Setting -DSQLITE_THREADSAFE=0 causes all of the mutex and thread-safety logic
in SQLite to be omitted.  This is the single compile-time option that makes
the most difference in optimizing the performance of SQLite.

<li><p><b>[SQLITE_DEFAULT_MEMSTATUS=0]</b>.
This setting causes the [sqlite3_status()] interfaces that track memory usage
to be disabled.  This helps the [sqlite3_malloc()] routines run much faster,
and since SQLite uses [sqlite3_malloc()] internally, this helps to make the
entire library faster.

<li><p><b>[SQLITE_DEFAULT_WAL_SYNCHRONOUS=1]</b>.
For maximum database safety following a power lose, the setting of
[PRAGMA synchronous=FULL] is recommended.  However, in [WAL mode], complete
database integrity is guaranteed with [PRAGMA synchronous=NORMAL].  With
[PRAGMA synchronous=NORMAL] in [WAL mode], recent changes to the database might
be rolled back by a power loss, but the database will not be corrupted.
Furthermore, transaction commit is much faster in WAL mode using
synchronous=NORMAL than with the default synchronous=FULL.  For these
reasons, it is recommended that the synchronous setting be changed from
FULL to NORMAL when switching to WAL mode.  This compile-time option will
accomplish that.

<li><p><b>[SQLITE_LIKE_DOESNT_MATCH_BLOBS]</b>.
Historically, SQLite has allowed BLOB operands to the [LIKE] and [GLOB]
operators.  But having a BLOB as an operand of [LIKE] or [GLOB] complicates
and slows the [LIKE optimization].  When this option is set, it means that
the LIKE and GLOB operators always return FALSE if either operand is a BLOB.
That simplifies the implementation of the [LIKE optimization] and allows
queries that use the [LIKE optimization] to run faster.

<li><p><b>[SQLITE_MAX_EXPR_DEPTH=0]</b>.
Setting the maximum expression parse-tree depth to zero disables all checking
of the expression parse-tree depth, which simplifies the code resulting in
faster execution, and helps the parse tree to use less memory.

<li><p><b>[SQLITE_OMIT_DECLTYPE]</b>.
By omitting the (seldom-needed) ability to return the declared type of
columns from the result set of query, [prepared statements] can be made
to consume less memory.

<li><p><b>[SQLITE_OMIT_DEPRECATED]</b>.
Omitting deprecated interfaces and features will not help SQLite to
run any faster.  It will reduce the library footprint, however.  And
it is the right thing to do.

<li><p><b>[SQLITE_OMIT_PROGRESS_CALLBACK]</b>.
The progress handler callback counter must be checked in the inner loop
of the [bytecode engine].  By omitting this interface, a single conditional
is removed from the inner loop of the [bytecode engine], helping SQL statements
to run slightly faster.

<li><p><b>[SQLITE_OMIT_SHARED_CACHE]</b>.
Omitting the possibility of using [shared cache] allows many conditionals
in performance-critical sections of the code to be eliminated.  This can
give a noticable improvement in performance.

<li><p><b>[SQLITE_USE_ALLOCA]</b>.
Make use of alloca() for dynamically allocating temporary stack space for 
use within a single function, on systems that support alloca().  Without
this option, temporary space is allocated from the heap.
</ol>

<p>When all of the recommended compile-time options above are used,
the SQLite library will be approximately 3% smaller and use about 5% fewer
CPU cycles.  So these options do not make a huge difference.  But in 
some design situations, every little bit helps.

<a name="osconfig"></a>
<h1> Platform Configuration</h1>

<tcl>
COMPILE_OPTION {_HAVE_SQLITE_CONFIG_H} {
  If the _HAVE_SQLITE_CONFIG_H macro is defined
  then the SQLite source code will attempt to #include a file named "config.h".
  The "config.h" file usually contains other configuration options, especially
  "HAVE_<i>INTERFACE</i>" type options generated by autoconf scripts.
}

COMPILE_OPTION {HAVE_FDATASYNC} {
  If the HAVE_FDATASYNC compile-time option is true, then the default [VFS]
  for unix systems will attempt to use fdatasync() instead of fsync() where
  appropriate.  If this flag is missing or false, then fsync() is always used.
}

COMPILE_OPTION {HAVE_GMTIME_R} {
  If the HAVE_GMTIME_R option is true and if [SQLITE_OMIT_DATETIME_FUNCS] is true,
  then the CURRENT_TIME, CURRENT_DATE, and CURRENT_TIMESTAMP keywords will use
  the threadsafe "gmtime_r()" interface rather than "gmtime()".  In the usual case
  where [SQLITE_OMIT_DATETIME_FUNCS] is not defined or is false, then the
  built-in [date and time functions] are used to implement the CURRENT_TIME,
  CURRENT_DATE, and CURRENT_TIMESTAMP keywords and neither gmtime_r() nor
  gmtime() is ever called.
}

COMPILE_OPTION {HAVE_ISNAN} {
  If the HAVE_ISNAN option is true, then SQLite invokes the system library isnan()
  function to determine if a double-precision floating point value is a NaN.
  If HAVE_ISNAN is undefined or false, then SQLite substitutes its own home-grown
  implementation of isnan().
}

COMPILE_OPTION {HAVE_LOCALTIME_R} {
  If the HAVE_LOCALTIME_R option is true, then SQLite uses the threadsafe
  localtime_r() library routine instead of localtime()
  to help implement the [localtime modifier]
  to the built-in [date and time functions].
}

COMPILE_OPTION {HAVE_LOCALTIME_S} {
  If the HAVE_LOCALTIME_S option is true, then SQLite uses the threadsafe
  localtime_s() library routine instead of localtime()
  to help implement the [localtime modifier]
  to the built-in [date and time functions].
}

COMPILE_OPTION {HAVE_MALLOC_USABLE_SIZE} {
  If the HAVE_MALLOC_USABLE_SIZE option is true, then SQLite tries uses the
  malloc_usable_size() interface to find the size of a memory allocation obtained
  from the standard-library malloc() or realloc() routines.  This option is only
  applicable if the standard-library malloc() is used.  On Apple systems,
  "zone malloc" is used instead, and so this option is not applicable.  And, of
  course, if the application supplies its own malloc implementation using
  [SQLITE_CONFIG_MALLOC] then this option has no effect.
  <p>
  If the HAVE_MALLOC_USABLE_SIZE option is omitted or is false, then SQLite 
  uses a wrapper around system malloc() and realloc() that enlarges each allocation
  by 8 bytes and writes the size of the allocation in the initial 8 bytes, and
  then SQLite also implements its own home-grown version of malloc_usable_size()
  that consults that 8-byte prefix to find the allocation size.  This approach
  works but it is suboptimal.  Applications are encouraged to use
  HAVE_MALLOC_USABLE_SIZE whenever possible.
}

COMPILE_OPTION {HAVE_STRCHRNUL} {
  If the HAVE_STRCHRNUL option is true, then SQLite uses the strchrnul() library
  function.  If this option is missing or false, then SQLite substitutes its own
  home-grown implementation of strchrnul().
}

COMPILE_OPTION {HAVE_USLEEP} {
  If the HAVE_USLEEP option is true, then the default unix VFS uses the
  usleep() system call to implement the xSleep method.  If this option is
  undefined or false, then xSleep on unix is implemented using sleep() which
  means that [sqlite3_sleep()] will have a minimum wait interval of 1000
  milliseconds regardless of its argument.  
}

COMPILE_OPTION {HAVE_UTIME} {
  If the HAVE_UTIME option is true, then the built-in but non-standard
  "unix-dotfile" VFS will use the utime() system call, instead of utimes(),
  to set the last access time on the lock file.
}

COMPILE_OPTION {SQLITE_BYTEORDER=<i>(0|1234|4321)</i>} {
  SQLite needs to know if the native byte order of the target CPU is
  big-endian or little-ending.  The SQLITE_BYTEORDER preprocessor is set
  to 4321 for big-endian machines and 1234 for little-endian machines, or
  it can be 0 to mean that the byte order must be determined at run-time.
  There are #ifdefs in the code that set SQLITE_BYTEORDER automatically
  for all common platforms and compilers.  However, it may be advantageous
  to set SQLITE_BYTEORDER appropriately when compiling SQLite for obscure
  targets.  If the target byte order cannot be determined at compile-time,
  then SQLite falls back to doing run-time checks, which always work, though
  with a small performance penalty.
}
</tcl>

<a name="defaults"></a>
<h1> Options To Set Default Parameter Values</h1>

<tcl>

COMPILE_OPTION {SQLITE_DEFAULT_AUTOMATIC_INDEX=<i>&lt;0 or 1&gt;</i>} {
  This macro determines the initial setting for [PRAGMA automatic_index]
  for newly opened [database connections].
  For all versions of SQLite through 3.7.17,
  automatic indices are normally enabled for new database connections if
  this compile-time option is omitted.
  However, that might change in future releases of SQLite.
  <p>See also: [SQLITE_OMIT_AUTOMATIC_INDEX]
}

COMPILE_OPTION {SQLITE_DEFAULT_AUTOVACUUM=<i>&lt;0 or 1 or 2&gt;</i>} {
  This macro determines if SQLite creates databases with the 
  [auto_vacuum] flag set by default to OFF (0), FULL (1), or
  INCREMENTAL (2). The default value is 0 meaning that databases
  are created with auto-vacuum turned off.
  In any case the compile-time default may be overridden by the 
  [PRAGMA auto_vacuum] command.
}

COMPILE_OPTION {SQLITE_DEFAULT_CACHE_SIZE=<i>&lt;N&gt;</i>} {
  This macro sets the default maximum size of the page-cache for each attached
  database.  A positive value means that the limit is N page.  If N is negative
  that means to limit the cache size to -N*1024 bytes.
  The suggested maximum cache size can be overridden by the 
  [PRAGMA cache_size] command. The default value is -2000, which translates
  into a maximum of 2048000 bytes per cache.
}

COMPILE_OPTION {SQLITE_DEFAULT_FILE_FORMAT=<i>&lt;1 or 4&gt;</i>} {
  The default [schema format number] used by SQLite when creating
  new database files is set by this macro.  The schema formats are all
  very similar.  The difference between formats 1 and 4 is that format
  4 understands [descending indices] and has a tighter encoding for
  boolean values.

  All versions of SQLite since 3.3.0 (2006-01-10)
  can read and write any schema format
  between 1 and 4.  But older versions of SQLite might not be able to
  read formats greater than 1.  So that older versions of SQLite will
  be able to read and write database files created by newer versions
  of SQLite, the default schema format was set to 1 for SQLite versions
  through 3.7.9 (2011-11-01).  Beginning with 
  [version 3.7.10] ([dateof:3.7.10]), the default
  schema format is 4.

  The schema format number for a new database can be set at runtime using
  the [PRAGMA legacy_file_format] command.
}

COMPILE_OPTION {SQLITE_DEFAULT_FILE_PERMISSIONS=<i>N</i>} {
  The default numeric file permissions for newly created database files
  under unix.  If not specified, the default is 0644 which means that
  the files is globally readable but only writable by the creator.
}

COMPILE_OPTION {SQLITE_DEFAULT_FOREIGN_KEYS=<i>&lt;0 or 1&gt;</i>} {
  This macro determines whether enforcement of 
  [foreign key constraints] is enabled or disabled by default for
  new database connections.  Each database connection can always turn
  enforcement of foreign key constraints on and off and run-time using
  the [foreign_keys pragma].  Enforcement of foreign key constraints
  is normally off by default, but if this compile-time parameter is
  set to 1, enforcement of foreign key constraints will be on by default.
}

COMPILE_OPTION {SQLITE_DEFAULT_MMAP_SIZE=<i>N</i>} {
  This macro sets the default limit on the amount of memory that
  will be used for memory-mapped I/O
  for each open database file.  If the <i>N</i>
  is zero, then memory mapped I/O is disabled by default.  This
  compile-time limit and the [SQLITE_MAX_MMAP_SIZE] can be modified 
  at start-time using the
  [sqlite3_config]([SQLITE_CONFIG_MMAP_SIZE]) call, or at run-time
  using the [mmap_size pragma].
}

COMPILE_OPTION {SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT=<i>&lt;bytes&gt;</i>} {
  This option sets the size limit on [rollback journal] files in
  [journal_mode pragma | persistent journal mode] and
  [locking_mode | exclusive locking mode] and on the size of the
  write-ahead log file in [WAL mode]. When this 
  compile-time option is omitted there is no upper bound on the
  size of the rollback journals or write-ahead logs.  
  The journal file size limit
  can be changed at run-time using the [journal_size_limit pragma].
}

COMPILE_OPTION {SQLITE_DEFAULT_LOCKING_MODE=<i>&lt;1 or 0&gt;</i>} {
  If set to 1, then the default [locking_mode] is set to EXCLUSIVE.
  If omitted or set to 0 then the default [locking_mode] is NORMAL.
}

COMPILE_OPTION {SQLITE_DEFAULT_LOOKASIDE=<i>SZ,N</i>} {
  Sets the default size of the [lookaside memory allocator] memory pool
  to N entries of SZ bytes each.  This setting can be modified at
  start-time using [sqlite3_config]([SQLITE_CONFIG_LOOKASIDE]) and/or
  as each [database connection] is opened using
  [sqlite3_db_config](db, [SQLITE_DBCONFIG_LOOKASIDE]).
}

COMPILE_OPTION {SQLITE_DEFAULT_MEMSTATUS=<i>&lt;1 or 0&gt;</i>} {
  This macro is used to determine whether or not the features enabled and
  disabled using the SQLITE_CONFIG_MEMSTATUS argument to [sqlite3_config()]
  are available by default. The default value is 1 ([SQLITE_CONFIG_MEMSTATUS]
  related features enabled).
  <p>
  The [sqlite3_memory_used()] and [sqlite3_memory_highwater()] interfaces,
  the [sqlite3_status64]([SQLITE_STATUS_MEMORY_USED]) interface,
  and the [SQLITE_MAX_MEMORY] compile-time option are all non-functional
  when memory usage tracking is disabled.
}

COMPILE_OPTION {SQLITE_DEFAULT_PCACHE_INITSZ=<i>N</i>} {
  This macro determines the number of pages initially allocated by the 
  page cache module when [SQLITE_CONFIG_PAGECACHE] configuration option is
  not use and memory for the page cache is obtained from [sqlite3_malloc()]
  instead.  The number of pages set by this macro are allocated in a single
  allocation, which reduces the load on the memory allocator.
}

COMPILE_OPTION {SQLITE_DEFAULT_PAGE_SIZE=<i>&lt;bytes&gt;</i>} {
  This macro is used to set the default page-size used when a
  database is created. The value assigned must be a power of 2. The
  default value is 4096. The compile-time default may be overridden at 
  runtime by the [PRAGMA page_size] command.
}

COMPILE_OPTION {SQLITE_DEFAULT_SYNCHRONOUS=<i>&lt;0-3&gt;</i>} {
  This macro determines the default value of the
  [PRAGMA synchronous] setting.  If not overridden at compile-time,
  the default setting is 2 (FULL).
}

COMPILE_OPTION {SQLITE_DEFAULT_WAL_SYNCHRONOUS=<i>&lt;0-3&gt;</i>} {
  This macro determines the default value of the
  [PRAGMA synchronous] setting for database files that open in
  [WAL mode].  If not overridden at compile-time, this value is the
  same as [SQLITE_DEFAULT_SYNCHRONOUS].
  <p>
  If SQLITE_DEFAULT_WAL_SYNCHRONOUS differs from SQLITE_DEFAULT_SYNCHRONOUS,
  and if the application has not modified the synchronous setting for
  the database file using the [PRAGMA synchronous] statement, then
  the synchronous setting is changed to value defined by
  SQLITE_DEFAULT_WAL_SYNCHRONOUS when the database connection switches
  into WAL mode for the first time.
  If the SQLITE_DEFAULT_WAL_SYNCHRONOUS value is not overridden at
  compile-time, then it will always be the same as
  [SQLITE_DEFAULT_SYNCHRONOUS] and so no automatic synchronous setting
  changes will ever occur.
}

COMPILE_OPTION {SQLITE_DEFAULT_WAL_AUTOCHECKPOINT=<i>&lt;pages&gt;</i>} {
  This macro sets the default page count for the [WAL]
  [checkpointing | automatic checkpointing] feature.  If unspecified,
  the default page count is 1000.
}

COMPILE_OPTION {SQLITE_DEFAULT_WORKER_THREADS=<i>N</i>} {
  This macro sets the default value for
  the [SQLITE_LIMIT_WORKER_THREADS] parameter.  The [SQLITE_LIMIT_WORKER_THREADS]
  parameter sets the maximum number of auxiliary threads that a single
  [prepared statement] will launch to assist it with a query.  If not specified,
  the default maximum is 0.
  The value set here cannot be more than [SQLITE_MAX_WORKER_THREADS].
}

COMPILE_OPTION {SQLITE_EXTRA_DURABLE} {
  The SQLITE_EXTRA_DURABLE compile-time option that used to cause the default
  [PRAGMA synchronous] setting to be EXTRA, rather than FULL.  This option
  is no longer supported.  Use
  [SQLITE_DEFAULT_SYNCHRONOUS|SQLITE_DEFAULT_SYNCHRONOUS=3] instead.
}

COMPILE_OPTION {SQLITE_FTS3_MAX_EXPR_DEPTH=<i>N</i>} {
  This macro sets the maximum depth of the search tree that corresponds to
  the right-hand side of the MATCH operator in an [FTS3] or [FTS4] full-text
  index.  The full-text search uses a recursive algorithm, so the depth of
  the tree is limited to prevent using too much stack space.  The default
  limit is 12.  This limit is sufficient for up to 4095 search terms on the
  right-hand side of the MATCH operator and it holds stack space usage to 
  less than 2000 bytes.
  <p>
  For ordinary FTS3/FTS4 queries, the search tree depth is approximately
  the base-2 logarithm of the number of terms in the right-hand side of the
  MATCH operator.  However, for [phrase queries] and [NEAR queries] the
  search tree depth is linear in the number of right-hand side terms.
  So the default depth limit of 12 is sufficient for up to 4095 ordinary
  terms on a MATCH, it is only sufficient for 11 or 12 phrase or NEAR
  terms.  Even so, the default is more than enough for most application.
}

COMPILE_OPTION {SQLITE_LIKE_DOESNT_MATCH_BLOBS} {
  This compile-time option causes the [LIKE] operator to always return 
  False if either operand is a BLOB.  The default behavior of [LIKE] 
  is that BLOB operands are cast to TEXT before the comparison is done.
  <p>
  This compile-time option makes SQLite run more efficiently when processing
  queries that use the [LIKE] operator, at the expense of breaking backwards
  compatibility.  However, the backwards compatibility break may be only
  a technicality.  There was a long-standing bug in the [LIKE] processing logic
  (see [https://www.sqlite.org/src/info/05f43be8fdda9f]) that caused it to
  misbehavior for BLOB operands and nobody observed that bug in nearly
  10 years of active use.  So for more users, it is probably safe to
  enable this compile-time option and thereby save a little CPU time
  on LIKE queries.
  <p>
  This compile-time option affects the SQL [LIKE] operator only and has
  no impact on the [sqlite3_strlike()] C-language interface.
}

COMPILE_OPTION {SQLITE_MAX_MEMORY=<i>N</i>} {
  This option limits the total amount of memory that SQLite will request
  from malloc() to <i>N</i> bytes.  Any attempt by SQLite to allocate
  new memory that would cause the sum of all allocations held by SQLite to exceed
  <i>N</i> bytes will result in an out-of-memory error.
  This is a hard upper limit.  See also the [sqlite3_soft_heap_limit()]
  interface.
  <p>
  This limit is only functional if memory usage statistics are available via
  the [sqlite3_memory_used()] and [sqlite3_status64]([SQLITE_STATUS_MEMORY_USED])
  interfaces.  Without that memory usage information, SQLite has no way of
  knowing when it is about to go over the limit, and thus is unable to prevent
  the excess memory allocation.  Memory usage tracking is turned on by default,
  but can be disabled at compile-time using the [SQLITE_DEFAULT_MEMSTATUS] option,
  or at start-time using [sqlite3_config]([SQLITE_CONFIG_MEMSTATUS]).
}

COMPILE_OPTION {SQLITE_MAX_MMAP_SIZE=<i>N</i>} {
  This macro sets a hard upper bound on the amount of address space that
  can be used by any single database for memory-mapped I/O.
  Setting this value to 0 completely disables memory-mapped I/O and
  causes logic associated with memory-mapped I/O to be omitted from the
  build.  This option does change the default memory-mapped I/O address
  space size (set by [SQLITE_DEFAULT_MMAP_SIZE] or
  sqlite3_config([SQLITE_CONFIG_MMAP_SIZE]) or the
  run-time memory-mapped I/O address space size (set by
  sqlite3_file_control([SQLITE_FCNTL_MMAP_SIZE]) or
  [PRAGMA mmap_size]) as long as those other settings are less than the
  maximum value defined here.
}

COMPILE_OPTION {SQLITE_MAX_SCHEMA_RETRY=<i>N</i>} {
  Whenever the database schema changes, prepared statements are automatically
  reprepared to accommodate the new schema.  There is a race condition here
  in that if one thread is constantly changing the schema, another thread
  might spin on reparses and repreparations of a prepared statement and
  never get any real work done.  This parameter prevents an infinite loop
  by forcing the spinning thread to give up after a fixed number of attempts
  at recompiling the prepared statement.  The default setting is 50 which is
  more than adequate for most applications.
}

COMPILE_OPTION {SQLITE_MAX_WORKER_THREADS=<i>N</i>} {
  Set an upper bound on the [sqlite3_limit](db,[SQLITE_LIMIT_WORKER_THREADS],N)
  setting that determines the maximum number of auxiliary threads that a single
  [prepared statement] will use to aid with CPU-intensive computations
  (mostly sorting).  See also the [SQLITE_DEFAULT_WORKER_THREADS] options.
}

COMPILE_OPTION {SQLITE_MINIMUM_FILE_DESCRIPTOR=<i>N</i>} {
  The unix [VFS] will never use a file descriptor less than <i>N</i>.  The
  default value of <i>N</i> is 3.
  <p>
  Avoiding the use of low-numbered file descriptors is a defense against
  accidental database corruption.  If a database file was opened using
  file descriptor 2, for example, and then an assert() failed and invoked
  write(2,...), that would likely cause database corruption by overwriting
  part of the database file with the assertion error message.  Using only
  higher-valued file descriptors avoids this potential problem.  The 
  protection against
  using low-numbered file descriptors can be disabled by setting this
  compile-time option to 0.
}

COMPILE_OPTION {SQLITE_POWERSAFE_OVERWRITE=<i>&lt;0 or 1&gt;</i>} {
  This option changes the default assumption about [powersafe overwrite]
  for the underlying filesystems for the unix and windows [VFSes].
  Setting SQLITE_POWERSAFE_OVERWRITE to 1 causes SQLite to assume that
  application-level writes cannot changes bytes outside the range of
  bytes written even if the write occurs just before a power loss.
  With SQLITE_POWERSAFE_OVERWRITE set to 0, SQLite assumes that other
  bytes in the same sector with a written byte might be changed or 
  damaged by a power loss.
}

COMPILE_OPTION {SQLITE_REVERSE_UNORDERED_SELECTS} {
  This option causes the [PRAGMA reverse_unordered_selects] setting to be
  enabled by default.  When enabled, [SELECT] statements that lack an
  ORDER BY clause will run in reverse order.<p>
  This option is useful for detecting when applications (incorrectly)
  assume that the order of rows in a SELECT without an ORDER BY clause
  will always be the same.
}

COMPILE_OPTION {SQLITE_SORTER_PMASZ=<i>N</i>} {
  If multi-threaded processing is enabled via the
  [PRAGMA threads] setting, then sort operations will
  attempt to start helper threads when the amount of content
  to be sorted exceeds the minimum of the [cache_size] and PMA Size
  determined by the [SQLITE_CONFIG_PMASZ] start-time option.
  This compile-time option sets the default value for the
  [SQLITE_CONFIG_PMASZ] start-time option.
  The default value is 250.
}

COMPILE_OPTION {SQLITE_STMTJRNL_SPILL=<i>N</i>} {
  The SQLITE_STMTJRNL_SPILL compile-time option determines the
  default setting of the [SQLITE_CONFIG_STMTJRNL_SPILL] start-time
  setting.  That setting determines the size threshold above which
  [statement journals] are moved from memory to disk.
}

COMPILE_OPTION {SQLITE_WIN32_MALLOC} {
  This option enables the use of the Windows Heap API functions for memory
  allocation instead of the standard library malloc() and free() routines.
}

COMPILE_OPTION {YYSTACKDEPTH=<i>&lt;max_depth&gt;</i>} {
  This macro sets the maximum depth of the LALR(1) stack used by
  the SQL parser within SQLite.  The default value is 100.  A typical
  application will use less than about 20 levels of the stack.
  Developers whose applications contain SQL statements that 
  need more than 100 LALR(1) stack entries should seriously
  consider refactoring their SQL as it is likely to be well beyond
  the ability of any human to comprehend.
}
</tcl>

<h1> Options To Set Size Limits</h1>

<p>There are compile-time options that will set upper bounds
on the sizes of various structures in SQLite.  The compile-time
options normally set a hard upper bound that can be changed
at run-time on individual [database connections] using the
[sqlite3_limit()] interface.</p>

<p>The compile-time options for setting upper bounds are
[limits | documented separately].  The following is a list of
the available settings:</p>

<ul>
<li> [SQLITE_MAX_ATTACHED]  </li>
<li> [SQLITE_MAX_COLUMN]  </li>
<li> [SQLITE_MAX_COMPOUND_SELECT]  </li>
<li> [SQLITE_MAX_EXPR_DEPTH]  </li>
<li> [SQLITE_MAX_FUNCTION_ARG]  </li>
<li> [SQLITE_MAX_LENGTH]  </li>
<li> [SQLITE_MAX_LIKE_PATTERN_LENGTH]  </li>
<li> [SQLITE_MAX_PAGE_COUNT]  </li>
<li> [SQLITE_MAX_SQL_LENGTH]  </li>
<li> [SQLITE_MAX_VARIABLE_NUMBER]  </li>
</ul>

<a name="controlfeatures"></a>
<h1> Options To Control Operating Characteristics</h1>

<tcl>
COMPILE_OPTION {SQLITE_4_BYTE_ALIGNED_MALLOC} {
  On most systems, the malloc() system call returns a buffer that is
  aligned to an 8-byte boundary.  But on some systems (ex: windows) malloc()
  returns 4-byte aligned pointer.  This compile-time option must be used
  on systems that return 4-byte aligned pointers from malloc().
}

COMPILE_OPTION {SQLITE_CASE_SENSITIVE_LIKE} {
  If this option is present, then the built-in [LIKE] operator will be
  case sensitive.  This same effect can be achieved at run-time using
  the [case_sensitive_like pragma].
}

COMPILE_OPTION {SQLITE_DIRECT_OVERFLOW_READ} {
  When this option is present, content contained in
  [overflow pages] of the database file is read directly from disk,
  bypassing the [page cache], during read transactions.  In applications
  that do a lot of reads of large BLOBs, this option might improve read
  performance.
}

COMPILE_OPTION {SQLITE_HAVE_ISNAN} {
  If this option is present, then SQLite will use the isnan() function from
  the system math library.  This is an alias for the [HAVE_ISNAN] configuration
  option.
}

COMPILE_OPTION {SQLITE_OS_OTHER=<i>&lt;0 or 1&gt;</i>} {
  The option causes SQLite to omit its built-in operating system interfaces
  for Unix, Windows, and OS/2.  The resulting library will have no default
  [sqlite3_vfs | operating system interface].  Applications must use
  [sqlite3_vfs_register()] to register an appropriate interface before
  using SQLite.  Applications must also supply implementations for the
  [sqlite3_os_init()] and [sqlite3_os_end()] interfaces.  The usual practice
  is for the supplied [sqlite3_os_init()] to invoke [sqlite3_vfs_register()].
  SQLite will automatically invoke [sqlite3_os_init()] when it initializes.

  This option is typically used when building SQLite for an embedded
  platform with a custom operating system.
}

COMPILE_OPTION {SQLITE_SECURE_DELETE} {
  This compile-time option changes the default setting of the
  [secure_delete pragma].  When this option is not used, secure_delete defaults
  to off.  When this option is present, secure_delete defaults to on.

  The secure_delete setting causes deleted content to be overwritten with
  zeros.  There is a small performance penalty since additional I/O
  must occur.  On the other hand, secure_delete can prevent fragments of 
  sensitive information from lingering in unused parts of the database file 
  after it has been deleted.  See the documentation on the
  [secure_delete pragma] for additional information.
}

COMPILE_OPTION {SQLITE_THREADSAFE=<i>&lt;0 or 1 or 2&gt;</i>} {
  This option controls whether or not code is included in SQLite to
  enable it to operate safely in a multithreaded environment.  The
  default is SQLITE_THREADSAFE=1 which is safe for use in a multithreaded
  environment.  When compiled with SQLITE_THREADSAFE=0 all mutexing code
  is omitted and it is unsafe to use SQLite in a multithreaded program.
  When compiled with SQLITE_THREADSAFE=2, SQLite can be used in a multithreaded
  program so long as no two threads attempt to use the same
  [database connection] (or any [prepared statements] derived from
  that database connection) at the same time.

  To put it another way, SQLITE_THREADSAFE=1 sets the default
  [threading mode] to Serialized.  SQLITE_THREADSAFE=2 sets the default
  [threading mode] to Multi-threaded.  And SQLITE_THREADSAFE=0 sets the
  [threading mode] to Single-threaded.

  The value of SQLITE_THREADSAFE can be determined at run-time
  using the [sqlite3_threadsafe()] interface.

  When SQLite has been compiled with SQLITE_THREADSAFE=1 or
  SQLITE_THREADSAFE=2 then the [threading mode]
  can be altered at run-time using the [sqlite3_config()] interface together
  with one of these verbs:

  <ul>
  <li>[SQLITE_CONFIG_SINGLETHREAD]
  <li>[SQLITE_CONFIG_MULTITHREAD]
  <li>[SQLITE_CONFIG_SERIALIZED]
  </ul>

  The [SQLITE_OPEN_NOMUTEX] and
  [SQLITE_OPEN_FULLMUTEX] flags to [sqlite3_open_v2()] can also be used
  to adjust the [threading mode] of individual [database connections]
  at run-time.

  Note that when SQLite is compiled with SQLITE_THREADSAFE=0, the code
  to make SQLite threadsafe is omitted from the build.  When this occurs,
  it is impossible to change the [threading mode] at start-time or run-time.

  See the [threading mode] documentation for additional information
  on aspects of using SQLite in a multithreaded environment.
}

COMPILE_OPTION {SQLITE_TEMP_STORE=<i>&lt;0 through 3&gt;</i>} {
  This option controls whether temporary files are stored on disk or
  in memory.  The meanings for various settings of this compile-time
  option are as follows:

  <table cellpadding="2" border="1">
  <tr><th>SQLITE_TEMP_STORE</th><th>Meaning</th></tr>
  <tr><td align="center">0</td><td>Always use temporary files</td></tr>
  <tr><td align="center">1</td><td>Use files by default but allow the
  [PRAGMA temp_store] command to override</td></tr>
  <tr><td align="center">2</td><td>Use memory by default but allow the
  [PRAGMA temp_store] command to override</td></tr>
  <tr><td align="center">3</td><td>Always use memory</td></tr>
  </table>

  The default setting is 1.  
  Additional information can be found in [tempstore | tempfiles.html].
}

COMPILE_OPTION {SQLITE_TRACE_SIZE_LIMIT=<i>N</i>} {
  If this macro is defined to a positive integer <i>N</i>, then the length of
  strings and BLOB that are expanded into parameters in the output of
  [sqlite3_trace()] is limited to <i>N</i> bytes.  
}

COMPILE_OPTION {SQLITE_USE_URI} {
  This option causes the [URI filename] process logic to be enabled by 
  default.  
}

</tcl>

<a name="enablefeatures"></a>
<h1> Options To Enable Features Normally Turned Off</h1>

<tcl>
COMPILE_OPTION {SQLITE_ALLOW_URI_AUTHORITY} {
  [URI filenames] normally throws an error if the authority section is
  not either empty or "localhost".  However, if SQLite is compiled with
  the SQLITE_ALLOW_URI_AUTHORITY compile-time option, then the URI is
  converted into a Uniform Naming Convention (UNC) filename and passed
  down to the underlying operating system that way.  
  <p>
  Some future versions of SQLite may change to enable this feature
  by default.
}
COMPILE_OPTION {SQLITE_ALLOW_COVERING_INDEX_SCAN=<i>&lt;0 or 1&gt;</i>} {
  This C-preprocess macro determines the default setting of the
  [SQLITE_CONFIG_COVERING_INDEX_SCAN] configuration setting.  It defaults
  to 1 (on) which means that covering indices are used for full table
  scans where possible, in order to reduce I/O and improve performance.
  However, the use of a covering index for a full scan will cause results
  to appear in a different order from legacy, which could cause some
  (incorrectly-coded) legacy applications to break.  Hence, the covering
  index scan option can be disabled at compile-time on systems that what
  to minimize their risk of exposing errors in legacy applications.
}

COMPILE_OPTION {SQLITE_ENABLE_8_3_NAMES=<i>&lt;1 or 2&gt;</i>} {
  If this C-preprocessor macro is defined, then extra code is
  included that allows SQLite to function on a filesystem that
  only support 8+3 filenames.  If the value of this macro is 1,
  then the default behavior is to continue to use long filenames and
  to only use 8+3 filenames if the 
  database connection is opened using [URI filenames] with
  the "<tt>8_3_names=1</tt>" query parameter.  If the value of
  this macro is 2, then the use of 8+3 filenames becomes the default
  but may be disabled on using the <tt>8_3_names=0</tt> query parameter.
}

COMPILE_OPTION {SQLITE_ENABLE_API_ARMOR} {
  When defined, this C-preprocessor macro activates extra code that
  attempts to detect misuse of the SQLite API, such as passing in NULL
  pointers to required parameters or using objects after they have been
  destroyed.
}

COMPILE_OPTION {SQLITE_ENABLE_ATOMIC_WRITE} {
  If this C-preprocessor macro is defined and if the
  xDeviceCharacteristics method of [sqlite3_io_methods] object for
  a database file reports (via one of the [SQLITE_IOCAP_ATOMIC] bits)
  that the filesystem supports atomic writes and if a transaction
  involves a change to only a single page of the database file,
  then the transaction commits with just a single write request of
  a single page of the database and no rollback journal is created
  or written.  On filesystems that support atomic writes, this
  optimization can result in significant speed improvements for
  small updates.  However, few filesystems support this capability
  and the code paths that check for this capability slow down write
  performance on systems that lack atomic write capability, so this
  feature is disabled by default.
}

COMPILE_OPTION {SQLITE_ENABLE_BATCH_ATOMIC_WRITE} {
  This compile-time option enables SQLite to take advantage batch
  atomic write capabilities in the underlying filesystem.  As of
  SQLite version 3.21.0 ([dateof:3.21.0]) this is only supported on
  [https://en.wikipedia.org/wiki/F2FS|F2FS].  However, the interface
  is implemented generically, using [sqlite3_file_control()] with
  [SQLITE_FCNTL_BEGIN_ATOMIC_WRITE] and [SQLITE_FCNTL_COMMIT_ATOMIC_WRITE]
  so the capability can be added to other filesystem times in the
  future.  When this option is enabled, SQLite automatically detects
  that the underlying filesystem supports batch atomic writes, and
  when it does so it avoids writing the [rollback journal] for transaction
  control.  This can make transactions over twice as fast, while
  simultaneously reducing wear on SSD storage devices.
<p>
  Future versions of SQLite might enable the batch-atomic-write
  capability by default, at which point this compile-time option
  will become superfluous.
}

COMPILE_OPTION {SQLITE_ENABLE_COLUMN_METADATA} {
  When this C-preprocessor macro is defined, SQLite includes some
  additional APIs that provide convenient access to meta-data about
  tables and queries.  The APIs that are enabled by this option are:

  <ul>
  <li> [sqlite3_column_database_name()] </li>
  <li> [sqlite3_column_database_name16()] </li>
  <li> [sqlite3_column_table_name()] </li>
  <li> [sqlite3_column_table_name16()] </li>
  <li> [sqlite3_column_origin_name()] </li>
  <li> [sqlite3_column_origin_name16()] </li>
  </ul>
}

COMPILE_OPTION {SQLITE_ENABLE_DBPAGE_VTAB} {
  This option enables the 
  [https://sqlite.org/src/file/src/dbpage.c|sqlite_dbpage virtual table].
}

COMPILE_OPTION {SQLITE_ENABLE_DBSTAT_VTAB} {
  This option enables the [dbstat virtual table].
}

COMPILE_OPTION {SQLITE_ENABLE_EXPLAIN_COMMENTS} {
  This option adds extra logic to SQLite that inserts comment text into the
  output of [EXPLAIN].  These extra comments use extra memory, thus
  making [prepared statements] larger and very slightly slower, and so they are
  turned off by default and in most application.  But some applications, such
  as the [command-line shell] for SQLite, value clarity of EXPLAIN output
  over raw performance and so this compile-time option is available to them.
  The SQLITE_ENABLE_EXPLAIN_COMMENTS compile-time option is also enabled
  automatically if [SQLITE_DEBUG] is enabled.
}


COMPILE_OPTION {SQLITE_ENABLE_FTS3} {
  When this option is defined in the [amalgamation], version 3
  of the full-text search engine is added to the build automatically.
}

COMPILE_OPTION {SQLITE_ENABLE_FTS3_PARENTHESIS} {
  This option modifies the query pattern parser in FTS3 such that it
  supports operators AND and NOT (in addition to the usual OR and NEAR)
  and also allows query expressions to contain nested parenthesis.
}

COMPILE_OPTION {SQLITE_ENABLE_FTS3_TOKENIZER} {
  This option enables the two-argument version of the [fts3_tokenizer()]
  interface.  The second argument to fts3_tokenizer() is suppose to be a
  pointer to a function (encoded as a BLOB) that implements an
  application defined tokenizer.  If hostile actors are able to run
  the two-argument version of fts3_tokenizer() with an arbitrary second
  argument, they could use crash or take control of the process. 
  <p>
  Because of security concerns, the two-argument fts3_tokenizer() feature 
  was disabled beginning with [Version 3.11.0] ([dateof:3.11.0])
  unless this compile-time option is used.
  [Version 3.12.0] ([dateof:3.12.0]) added the 
  [sqlite3_db_config](db,[SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER],1,0) interface
  that activates the two-argument version of [fts3_tokenizer()]
  for a specific [database connection] at run-time.
}

COMPILE_OPTION {SQLITE_ENABLE_FTS4} {
  When this option is defined in the [amalgamation], versions 3 and 4
  of the full-text search engine is added to the build automatically.
}

COMPILE_OPTION {SQLITE_ENABLE_FTS5} {
  When this option is defined in the [amalgamation], versions 5
  of the full-text search engine ([fts5]) is added to the build automatically.
}

COMPILE_OPTION {SQLITE_ENABLE_ICU} {
  This option causes the 
  [http://www.icu-project.org/ | International Components for Unicode]
  or "ICU" extension to SQLite to be added to the build.  
}

COMPILE_OPTION {SQLITE_ENABLE_IOTRACE} {
  When both the SQLite core and the [Command Line Interface] (CLI) are both 
  compiled with this option, then the CLI provides an extra command
  named ".iotrace" that provides a low-level log of I/O activity.
  This option is experimental and may be discontinued in a future release.
}

COMPILE_OPTION {SQLITE_ENABLE_JSON1} {
  When this option is defined in the [amalgamation], the
  [JSON SQL functions] are added to the build automatically.
}

COMPILE_OPTION {SQLITE_ENABLE_LOCKING_STYLE} {
  This option enables additional logic in the OS interface layer for
  Mac OS X. The additional logic attempts to determine the type of the
  underlying filesystem and choose and alternative locking strategy
  that works correctly for that filesystem type. Five locking strategies 
  are available:

  <ul>
    <li> POSIX locking style. This is the default locking style and the
         style used by other (non Mac OS X) Unixes. Locks are obtained and 
         released using the fcntl() system call.

    <li> AFP locking style. This locking style is used for network file 
         systems that use the AFP (Apple Filing Protocol) protocol. Locks
         are obtained by calling the library function _AFPFSSetLock().

    <li> Flock locking style. This is used for file-systems that do not
         support POSIX locking style. Locks are obtained and released using
         the flock() system call.

    <li> Dot-file locking style. This locking style is used when neither
         flock nor POSIX locking styles are supported by the file system.
         Database locks are obtained by creating and entry in the file-system
         at a well-known location relative to the database file (a "dot-file")
         and relinquished by deleting the same file.

    <li> No locking style. If none of the above can be supported, this 
         locking style is used. No database locking mechanism is used. When
         this system is used it is not safe for a single database to be
         accessed by multiple clients.
  </ul>

  Additionally, five extra [VFS] implementations are provided as well as the
  default. By specifying one of the extra VFS implementations 
  when calling [sqlite3_open_v2()], an application may bypass the file-system
  detection logic and explicitly select one of the above locking styles. The
  five extra [VFS] implementations are called "unix-posix", "unix-afp",
  "unix-flock", "unix-dotfile" and "unix-none".
}

COMPILE_OPTION {SQLITE_ENABLE_MEMORY_MANAGEMENT} {
  This option adds extra logic to SQLite that allows it to release unused
  memory upon request.  This option must be enabled in order for the
  [sqlite3_release_memory()] interface to work.  If this compile-time
  option is not used, the [sqlite3_release_memory()] interface is a 
  no-op.
}

COMPILE_OPTION {SQLITE_ENABLE_MEMSYS3} {
  This option includes code in SQLite that implements an alternative
  memory allocator.  This alternative memory allocator is only engaged
  when the [SQLITE_CONFIG_HEAP] option to [sqlite3_config()] is used to
  supply a large chunk of memory from which all memory allocations are
  taken.
  The MEMSYS3 memory allocator uses a hybrid allocation algorithm 
  patterned after dlmalloc().   Only one of SQLITE_ENABLE_MEMSYS3 and 
  SQLITE_ENABLE_MEMSYS5 may be enabled at once.
}

COMPILE_OPTION {SQLITE_ENABLE_MEMSYS5} {
  This option includes code in SQLite that implements an alternative
  memory allocator.  This alternative memory allocator is only engaged
  when the [SQLITE_CONFIG_HEAP] option to [sqlite3_config()] is used to
  supply a large chunk of memory from which all memory allocations are
  taken.
  The MEMSYS5 module rounds all allocations up to the next power
  of two and uses a first-fit, buddy-allocator algorithm
  that provides strong guarantees against fragmentation and breakdown
  subject to certain operating constraints.
}

COMPILE_OPTION {SQLITE_ENABLE_NULL_TRIM} {
  This option enables an optimization that omits NULL columns at
  the ends of rows, for a space savings on disk.
  <p>
  Databases generated with this option enabled are not readable
  by SQLite version 3.1.6 ([dateof:3.1.6]) and earlier.  Also,
  databases generated with this option enabled are prone to
  triggering the
  [https://www.sqlite.org/src/info/e6e962d6b0f06f46e|e6e962d6b0f06f46]
  bug in the [sqlite3_blob_reopen()] interface.  For those reasons,
  this optimization is disabled by default.  However, this optimization
  may be enabled by default in a future release of SQLite.
}

COMPILE_OPTION {SQLITE_ENABLE_OFFSET_SQL_FUNC} {
  This option enables support for the [sqlite_offset(X)] SQL function.
  <p>
  The [sqlite_offset(X)] SQL function requires a new interface on the
  B-tree storage engine, a new opcode in the [virtual machine] that
  runs SQL statements, and a new conditional in a critical path of the
  code generator.  To avoid that overhead in applications that do not
  need the utility of sqlite_offset(X), the function is disabled by
  default.
}

COMPILE_OPTION {SQLITE_ENABLE_PREUPDATE_HOOK} {
  This option enables 
  [sqlite3_preupdate_hook|several new APIs] that provide callbacks
  prior to any change to a [rowid table].  The callbacks can be used
  to record the state of the row before the change occurs.
  <p>The action of the preupdate hook is similar to the
  [sqlite3_update_hook|update hook] except that the callback is
  invoked before the change, not afterwards, and the preupdate
  hook interfaces are omitted unless this compile-time option is
  used.
  <p>The preupdate hook interfaces were originally added to
  support the [session] extension.
}

COMPILE_OPTION {SQLITE_ENABLE_QPSG} {
  This option causes the [query planner stability guarantee] (QPSG) to
  be on by default.  Normally the QPSG is off and must be activated
  at run-time using the [SQLITE_DBCONFIG_ENABLE_QPSG] option to the
  [sqlite3_db_config()] interface.
}

COMPILE_OPTION {SQLITE_ENABLE_RBU} {
  Enable the code the implements the [RBU extension].
}

COMPILE_OPTION {SQLITE_ENABLE_RTREE} {
  This option causes SQLite to include support for the
  [rtree | R*Tree index extension].
}

COMPILE_OPTION {SQLITE_ENABLE_SESSION} {
  This option enables the [session extension].
}

COMPILE_OPTION {SQLITE_ENABLE_STMT_SCANSTATUS} {
  This option enables the [sqlite3_stmt_scanstatus()] interface.  The
  [sqlite3_stmt_scanstatus()] interface is normally omitted from the build
  because it imposes a small performance penalty, even on statements that
  do not use the feature.
}

COMPILE_OPTION {SQLITE_ENABLE_STMTVTAB} {
  This compile-time option enables the [SQLITE_STMT virtual table] logic.
}

COMPILE_OPTION {SQLITE_RTREE_INT_ONLY} {
  This compile-time option is deprecated and untested.
}

COMPILE_OPTION {SQLITE_ENABLE_SQLLOG} {
  This option enables extra code (especially the [SQLITE_CONFIG_SQLLOG]
  option to [sqlite3_config()]) that can be used to create logs of all
  SQLite processing performed by an application.  These logs can be useful
  in doing off-line analysis of the behavior of an application, and especially
  for performance analysis.  In order for the SQLITE_ENABLE_SQLLOG option to 
  be useful, some extra code is required.  The 
  <a href="http://www.sqlite.org/src/doc/trunk/src/test_sqllog.c">"test_sqllog.c"</a>
  source code
  file in the SQLite source tree is a working example of the required extra
  code.  On unix and windows systems, a developer can append the text of the
  "test_sqllog.c" source code file to the end of an "sqlite3.c" amalgamation,
  recompile the application using the -DSQLITE_ENABLE_SQLLOG option, then 
  control logging using environment variables.  See the header comment on 
  the "test_sqllog.c" source file for additional detail.  
}

COMPILE_OPTION {SQLITE_ENABLE_STAT2} {
  This option used to cause the [ANALYZE] command to collect
  index histogram data in the <b>sqlite_stat2</b> table.  But that
  functionality was superceded by [SQLITE_ENABLE_STAT3] as of
  SQLite [version 3.7.9] ([dateof:3.7.9]).  
  The SQLITE_ENABLE_STAT2 compile-time option
  is now a no-op.
}

COMPILE_OPTION {SQLITE_ENABLE_STAT3} {
  This option adds additional logic to the [ANALYZE] command and to
  the [query planner] that can help SQLite to chose a better query plan
  under certain situations.  The [ANALYZE] command is enhanced to collect
  histogram data from the left-most column of each index and store that data
  in the [sqlite_stat3] table.  The query planner will then use the
  histogram data to help it make better index choices.  Note, however,
  that the use of histogram data in query planner violates the
  [query planner stability guarantee] which is important to some applications.
  <p>
}

COMPILE_OPTION {SQLITE_ENABLE_STAT4} {
  This option adds additional logic to the [ANALYZE] command and to
  the [query planner] that can help SQLite to chose a better query plan
  under certain situations.  The [ANALYZE] command is enhanced to collect
  histogram data from all columns of every index and store that data
  in the [sqlite_stat4] table.  The query planner will then use the
  histogram data to help it make better index choices.  The downside of
  this compile-time option is that it violates the
  [query planner stability guarantee] making it more difficult to ensure
  consistent performance in mass-produced applications.
  <p>
  SQLITE_ENABLE_STAT4 is an enhancement of [SQLITE_ENABLE_STAT3].  STAT3
  only recorded histogram data for the left-most column of each index
  whereas the STAT4 enhancement records histogram data from all columns
  of each index.
  The [SQLITE_ENABLE_STAT3] compile-time option is a no-op and is ignored
  if the SQLITE_ENABLE_STAT4 compile-time option is used.
}

COMPILE_OPTION {SQLITE_ENABLE_TREE_EXPLAIN} {
  This compile-time option is no longer used.
}

COMPILE_OPTION {SQLITE_ENABLE_UPDATE_DELETE_LIMIT} {
  This option enables an optional ORDER BY and LIMIT clause on 
  [UPDATE] and [DELETE] statements.

  <p>If this option is defined, then it must also be 
  defined when using the [Lemon parser generator] tool to generate a parse.c
  file. Because of this, this option may only be used when the library is built
  from source, not from the [amalgamation] or from the collection of
  pre-packaged C files provided for non-Unix like platforms on the website.
  </p>
}

COMPILE_OPTION {SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION} {
  When the SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION compile-time option is
  activated, SQLite will suppress "unknown function" errors when running
  an [EXPLAIN] or [EXPLAIN QUERY PLAN].  Instead of throwing an error,
  SQLite will insert a substitute no-op function named "unknown()".
  The substitution of "unknown()" in place of unrecognized functions
  only occurs on [EXPLAIN] and [EXPLAIN QUERY PLAN], not on ordinary
  statements.
  <p>
  When used in the [command-line shell], the
  SQLITE_ENABLE_UNKNOWN_SQL_FUNCTION feature allows SQL text that contains
  application-defined functions to be pasted into the shell for 
  analysis and debugging without having to create and load an
  extension that implements the application-defined functions.
}

COMPILE_OPTION {SQLITE_ENABLE_UNLOCK_NOTIFY} {
  This option enables the [sqlite3_unlock_notify()] interface and
  its associated functionality.  See the documentation titled
  [Using the SQLite Unlock Notification Feature] for additional
  information.
}

COMPILE_OPTION {SQLITE_INTROSPECTION_PRAGMAS} {
  This option adds some extra PRAGMA statements such as
  [PRAGMA function_list], [PRAGMA module_list], and
  [PRAGMA pragma_list].
}

COMPILE_OPTION {SQLITE_SOUNDEX} {
  This option enables the [soundex() SQL function].
}

COMPILE_OPTION {SQLITE_USE_ALLOCA} {
  If this option is enabled, then the alloca() memory allocator will be
  used in a few situations where it is appropriate.  This results in a slightly
  smaller and faster binary.  The SQLITE_USE_ALLOCA compile-time only only 
  works, of course, on systems that support alloca().
}

COMPILE_OPTION {SQLITE_USE_FCNTL_TRACE} {
  This option causes SQLite to issue extra [SQLITE_FCNTL_TRACE] file controls
  to provide supplementary information to the VFS.  The "vfslog.c" extension
  makes use of this to provide enhanced logs of VFS activity.
}

COMPILE_OPTION {SQLITE_USE_ZLIB} {
  This option causes some extensions to link against the 
  [https://zlib.net|zlib compression library].
  <p>
  This option has no affect on the SQLite core.  It is only used by extensions.
  This is option is necessary for the commpression and decompression
  functions that are part of [SQL Archive] support in the
  [command-line shell].
  <p>
  When compiling with this option, it will normally
  be necessary to add a linker option to include the zlib library in the
  build.  Normal this option is "-lz" but might be different on different
  systems.
  <p>
  When building with MSVC on Windows systems, one can put the zlib source
  code in the compat/zlib subdirectory of the source tree and then add
  the USE_ZLIB=1 option to the nmake command to cause the The Makefile.msc
  to automatically build and use an appropriate zlib library implementation.
}

COMPILE_OPTION {YYTRACKMAXSTACKDEPTH} {
  This option causes the LALR(1) parser stack depth to be tracked
  and reported using the [sqlite3_status]([SQLITE_STATUS_PARSER_STACK],...)
  interface.  SQLite's LALR(1) parser has a fixed stack depth
  (determined at compile-time using the [YYSTACKDEPTH] options).
  This option can be used to help determine if an application is
  getting close to exceeding the maximum LALR(1) stack depth.
}
</tcl>

<a name="disablefeatures"></a>
<h1> Options To Disable Features Normally Turned On</h1>

<tcl>
COMPILE_OPTION {SQLITE_DISABLE_LFS} {
  If this C-preprocessor macro is defined, large file support
  is disabled.
}

COMPILE_OPTION {SQLITE_DISABLE_DIRSYNC} {
  If this C-preprocessor macro is defined, directory syncs
  are disabled.  SQLite typically attempts to sync the parent
  directory when a file is deleted to ensure the directory
  entries are updated immediately on disk.
}

COMPILE_OPTION {SQLITE_DISABLE_FTS3_UNICODE} {
  If this C-preprocessor macro is defined, the [unicode61] tokenizer
  in [FTS3] is omitted from the build and is unavailable to 
  applications.
}

COMPILE_OPTION {SQLITE_DISABLE_FTS4_DEFERRED} {
  If this C-preprocessor macro disables the "deferred token" optimization
  in [FTS4].  The "deferred token" optimization avoids loading massive
  posting lists for terms that are in most documents of the collection
  and instead simply scans for those tokens in the document source.  [FTS4]
  should get exactly the same answer both with and without this optimization.
}

COMPILE_OPTION {SQLITE_DISABLE_INTRINSIC} {
  This option disables the use of compiler-specific built-in functions
  such as __builtin_bswap32() and __builtin_add_overflow() in GCC and Clang, 
  or _byteswap_ulong() and _ReadWriteBarrier() with MSVC.  
}
</tcl>

<tcl>
  hd_fragment "omitfeatures"
  hd_keywords "omitfeatures"
</tcl>
<h1> Options To Omit Features</h1>

<p>The following options can be used to 
[relfootprint | reduce the size of the compiled library]
by omitting unused features. This is probably only useful
in embedded systems where space is especially tight, as even with all
features included the SQLite library is relatively small. Don't forget
to tell your compiler to optimize for binary size! (the -Os option if
using GCC).  Telling your compiler to optimize for size usually has
a much larger impact on library footprint than employing any of these
compile-time options.  You should also verify that 
<a href="#debugoptions">debugging options</a> are disabled.</p>

<p>The macros in this section do not require values. The following 
compilation switches all have the same effect:<br>
-DSQLITE_OMIT_ALTERTABLE<br>
-DSQLITE_OMIT_ALTERTABLE=1<br>
-DSQLITE_OMIT_ALTERTABLE=0
</p>

<p>If any of these options are defined, then the same set of SQLITE_OMIT_*
options must also be defined when using the [Lemon parser generator]
tool to generate the
parse.c file and when compiling the 'mkkeywordhash' tool which generates 
the keywordhash.h file.
Because of this, these options may only be used when the library is built
from canonical source, not from the [amalgamation].
Some SQLITE_OMIT_* options might work, or appear to work, when used with
the [amalgamation].  But this is not guaranteed.  In general, always compile
from canonical sources in order to take advantage of SQLITE_OMIT_* options.
</p>

<blockquote>
<i><b>Important Note:</b> The SQLITE_OMIT_* options may not work with the
[amalgamation].  SQLITE_OMIT_* compile-time
options usually work correctly only when SQLite is built from canonical 
source files.
</i>
</blockquote>


<p>Special versions of the SQLite amalgamation that do work with a
predetermined set of SQLITE_OMIT_* options can be generated.  To do so,
make a copy of the Makefile.linux-gcc makefile template in the canonical
source code distribution.  Change the name of your copy to simply "Makefile".
Then edit "Makefile" to set up appropriate compile-time options.  Then
type:
<codeblock>
make clean; make sqlite3.c
</codeblock>
<p>The resulting "sqlite3.c" amalgamation code file (and its associated
header file "sqlite3.h") can then be moved to a non-unix platform
for final compilation using a native compiler.</p>

<p>The SQLITE_OMIT_* options are unsupported.  By this we mean that
an SQLITE_OMIT_* option that omits code from the build in the current
release might become a no-op in the next release.  Or the other way around:
an SQLITE_OMIT_* that is a no-op in the current release might cause code
to be excluded in the next release.  Also, not all SQLITE_OMIT_* options
are tested.  Some SQLITE_OMIT_* options might cause SQLite to malfunction
and/or provide incorrect answers.

<blockquote>
<i><b>Important Note:</b>
The SQLITE_OMIT_* compile-time options are mostly unsupported.
</i></blockquote>

<p>The following are the available OMIT options:

<tcl>
COMPILE_OPTION {SQLITE_OMIT_ALTERTABLE} {
  When this option is defined, the 
  [ALTER TABLE] command is not included in the 
  library. Executing an [ALTER TABLE] statement causes a parse error.
}

COMPILE_OPTION {SQLITE_OMIT_ANALYZE} {
  When this option is defined, the [ANALYZE] command is omitted from
  the build.
}

COMPILE_OPTION {SQLITE_OMIT_ATTACH} {
  When this option is defined, the [ATTACH] and [DETACH] commands are
  omitted from the build.
}

COMPILE_OPTION {SQLITE_OMIT_AUTHORIZATION} {
  Defining this option omits the authorization callback feature from the
  library. The [sqlite3_set_authorizer()] API function is not present
  in the library.
}

COMPILE_OPTION {SQLITE_OMIT_AUTOINCREMENT} {
  This option is omits the [AUTOINCREMENT] feature. 
  When this is macro is defined, columns declared as 
  "[INTEGER PRIMARY KEY] AUTOINCREMENT"
  behave in the same way as columns declared as "[INTEGER PRIMARY KEY]" when a 
  NULL is inserted. The sqlite_sequence system table is neither created, nor
  respected if it already exists.
}

COMPILE_OPTION {SQLITE_OMIT_AUTOINIT} {
  For backwards compatibility with older versions of SQLite that lack
  the [sqlite3_initialize()] interface, the [sqlite3_initialize()] interface
  is called automatically upon entry to certain key interfaces such as
  [sqlite3_open()], [sqlite3_vfs_register()], and [sqlite3_mprintf()].
  The overhead of invoking [sqlite3_initialize()] automatically in this
  way may be omitted by building SQLite with the SQLITE_OMIT_AUTOINIT
  C-preprocessor macro.  When built using SQLITE_OMIT_AUTOINIT, SQLite
  will not automatically initialize itself and the application is required
  to invoke [sqlite3_initialize()] directly prior to beginning use of the
  SQLite library.
}

COMPILE_OPTION {SQLITE_OMIT_AUTOMATIC_INDEX} {
  This option is used to omit the 
  [automatic indexing] functionality.
  See also: [SQLITE_DEFAULT_AUTOMATIC_INDEX].
}

COMPILE_OPTION {SQLITE_OMIT_AUTORESET} {
  By default, the [sqlite3_step()] interface will automatically invoke
  [sqlite3_reset()] to reset the [prepared statement] if necessary.  This
  compile-time option changes that behavior so that [sqlite3_step()] will
  return [SQLITE_MISUSE] if it called again after returning anything other
  than [SQLITE_ROW], [SQLITE_BUSY], or [SQLITE_LOCKED] unless there was an
  intervening call to [sqlite3_reset()].

  In SQLite [version 3.6.23.1] ([dateof:3.6.23.1])
  and earlier, [sqlite3_step()] used to always
  return [SQLITE_MISUSE] if it was invoked again after returning anything
  other than [SQLITE_ROW] without an intervening call to [sqlite3_reset()].
  This caused problems on some poorly written smartphone applications which
  did not correctly handle the [SQLITE_LOCKED] and [SQLITE_BUSY] error 
  returns.  Rather than fix the many defective smartphone applications, 
  the behavior of SQLite was changed in 3.6.23.2 to automatically reset
  the prepared statement.  But that changed caused issues in other 
  improperly implemented applications that were actually looking
  for an [SQLITE_MISUSE] return to terminate their query loops.  (Anytime
  an application gets an SQLITE_MISUSE error code from SQLite, that means the
  application is misusing the SQLite interface and is thus incorrectly
  implemented.)  The SQLITE_OMIT_AUTORESET interface was added to SQLite
  [version 3.7.5] ([dateof:3.7.5]) in an effort to get all of the (broken)
  applications to work again without having to actually fix the applications.
}

COMPILE_OPTION {SQLITE_OMIT_AUTOVACUUM} {
  If this option is defined, the library cannot create or write to 
  databases that support [auto_vacuum].
  Executing a [PRAGMA auto_vacuum] statement is not an error
  (since unknown PRAGMAs are silently ignored), but does not return a value
  or modify the auto-vacuum flag in the database file. If a database that
  supports auto-vacuum is opened by a library compiled with this option, it
  is automatically opened in read-only mode.
}

COMPILE_OPTION {SQLITE_OMIT_BETWEEN_OPTIMIZATION} {
  This option disables the use of indices with WHERE clause terms
  that employ the BETWEEN operator.
}

COMPILE_OPTION {SQLITE_OMIT_BLOB_LITERAL} {
  When this option is defined, it is not possible to specify a blob in
  an SQL statement using the X'ABCD' syntax.
}

COMPILE_OPTION {SQLITE_OMIT_BTREECOUNT} {
  When this option is defined, an optimization that accelerates counting
  all entries in a table (in other words, an optimization that helps
  "SELECT count(*) FROM table" run faster) is omitted.
}

COMPILE_OPTION {SQLITE_OMIT_BUILTIN_TEST} {
  This compile-time option has been renamed to [SQLITE_UNTESTABLE].
}

COMPILE_OPTION {SQLITE_OMIT_CAST} {
  This option causes SQLite to omit support for the CAST operator.
}

COMPILE_OPTION {SQLITE_OMIT_CHECK} {
  This option causes SQLite to omit support for CHECK constraints.
  The parser will still accept CHECK constraints in SQL statements,
  they will just not be enforced.
}

COMPILE_OPTION {SQLITE_OMIT_COMPILEOPTION_DIAGS} {
  This option is used to omit the compile-time option diagnostics available
  in SQLite, including the [sqlite3_compileoption_used()] and
  [sqlite3_compileoption_get()] C/C++ functions, the
  [sqlite_compileoption_used()] and [sqlite_compileoption_get()] SQL functions,
  and the [compile_options pragma].
}

COMPILE_OPTION {SQLITE_OMIT_COMPLETE} {
  This option causes the [sqlite3_complete()] and [sqlite3_complete16()]
  interfaces to be omitted.
}

COMPILE_OPTION {SQLITE_OMIT_COMPOUND_SELECT} {
  This option is used to omit the compound [SELECT] functionality. 
  [SELECT] statements that use the 
  UNION, UNION ALL, INTERSECT or EXCEPT compound SELECT operators will 
  cause a parse error.

  An [INSERT] statement with multiple values in the VALUES clause is
  implemented internally as a compound SELECT.  Hence, this option also
  disables the ability to insert more than a single row using an
  INSERT INTO ... VALUES ... statement.
}

COMPILE_OPTION {SQLITE_OMIT_CTE} {
  This option causes support for [common table expressions] to be omitted.
}



COMPILE_OPTION {SQLITE_OMIT_DATETIME_FUNCS} {
  If this option is defined, SQLite's built-in date and time manipulation
  functions are omitted. Specifically, the SQL functions julianday(), date(),
  time(), datetime() and strftime() are not available. The default column
  values CURRENT_TIME, CURRENT_DATE and CURRENT_TIMESTAMP are still available.
}

COMPILE_OPTION {SQLITE_OMIT_DECLTYPE} {
  This option causes SQLite to omit support for the
  [sqlite3_column_decltype()] and [sqlite3_column_decltype16()]
  interfaces.
}

COMPILE_OPTION {SQLITE_OMIT_DEPRECATED} {
  This option causes SQLite to omit support for interfaces
  marked as deprecated.  This includes 
  [sqlite3_aggregate_count()],
  [sqlite3_expired()],
  [sqlite3_transfer_bindings()],
  [sqlite3_global_recover()],
  [sqlite3_thread_cleanup()] and
  [sqlite3_memory_alarm()] interfaces.
}

COMPILE_OPTION {SQLITE_OMIT_DISKIO} {
  This option omits all support for writing to the disk and forces
  databases to exist in memory only.  This option has not been 
  maintained and probably does not work with newer versions of SQLite.
}

COMPILE_OPTION {SQLITE_OMIT_EXPLAIN} {
  Defining this option causes the [EXPLAIN] command to be omitted from the
  library. Attempting to execute an [EXPLAIN] statement will cause a parse
  error.
}

COMPILE_OPTION {SQLITE_OMIT_FLAG_PRAGMAS} {
  This option omits support for a subset of [PRAGMA] commands that
  query and set boolean properties.
}

COMPILE_OPTION {SQLITE_OMIT_FLOATING_POINT} {
  This option is used to omit floating-point number support from the SQLite
  library. When specified, specifying a floating point number as a literal 
  (i.e. "1.01") results in a parse error.

  <p>In the future, this option may also disable other floating point 
  functionality, for example the [sqlite3_result_double()], 
  [sqlite3_bind_double()], [sqlite3_value_double()] and
  [sqlite3_column_double()] API functions.
  </p>
}

COMPILE_OPTION {SQLITE_OMIT_FOREIGN_KEY} {
  If this option is defined, then [foreign key constraint] syntax is
  not recognized.
}

COMPILE_OPTION {SQLITE_OMIT_GET_TABLE} {
  This option causes support for [sqlite3_get_table()] and
  [sqlite3_free_table()] to be omitted.
}

COMPILE_OPTION {SQLITE_OMIT_INCRBLOB} {
  This option causes support for [sqlite3_blob | incremental BLOB I/O]
  to be omitted.
}

COMPILE_OPTION {SQLITE_OMIT_INTEGRITY_CHECK} {
  This option omits support for the [integrity_check pragma].
}

COMPILE_OPTION {SQLITE_OMIT_LIKE_OPTIMIZATION} {
  This option disables the ability of SQLite to use indices to help
  resolve [LIKE] and [GLOB] operators in a WHERE clause.
}

COMPILE_OPTION {SQLITE_OMIT_LOAD_EXTENSION} {
  This option omits the entire extension loading mechanism from
  SQLite, including [sqlite3_enable_load_extension()] and
  [sqlite3_load_extension()] interfaces.
}

COMPILE_OPTION {SQLITE_OMIT_LOCALTIME} {
  This option omits the "localtime" modifier from the date and time
  functions.  This option is sometimes useful when trying to compile
  the date and time functions on a platform that does not support the
  concept of local time.
}

COMPILE_OPTION {SQLITE_OMIT_LOOKASIDE} {
  This option omits the [lookaside memory allocator].
}

COMPILE_OPTION {SQLITE_OMIT_MEMORYDB} {
  When this is defined, the library does not respect the special database
  name ":memory:" (normally used to create an [in-memory database]). If 
  ":memory:" is passed to [sqlite3_open()], [sqlite3_open16()], or
  [sqlite3_open_v2()], a file with this name will be 
  opened or created.
}

COMPILE_OPTION {SQLITE_OMIT_OR_OPTIMIZATION} {
  This option disables the ability of SQLite to use an index together
  with terms of a WHERE clause connected by the OR operator.
}

COMPILE_OPTION {SQLITE_OMIT_PAGER_PRAGMAS} {
  Defining this option omits pragmas related to the pager subsystem from 
  the build.
}

COMPILE_OPTION {SQLITE_OMIT_PRAGMA} {
  This option is used to omit the [PRAGMA] command
  from the library. Note that it is useful to define the macros that omit
  specific pragmas in addition to this, as they may also remove supporting code
  in other sub-systems. This macro removes the [PRAGMA] command only.
}

COMPILE_OPTION {SQLITE_OMIT_PROGRESS_CALLBACK} {
  This option may be defined to omit the capability to issue "progress" 
  callbacks during long-running SQL statements. The 
  [sqlite3_progress_handler()]
  API function is not present in the library.
}

COMPILE_OPTION {SQLITE_OMIT_QUICKBALANCE} {
  This option omits an alternative, faster B-Tree balancing routine.
  Using this option makes SQLite slightly smaller at the expense of
  making it run slightly slower.
}

COMPILE_OPTION {SQLITE_OMIT_REINDEX} {
  When this option is defined, the [REINDEX]
  command is not included in the library.
  Executing a [REINDEX] statement causes 
  a parse error.
}

COMPILE_OPTION {SQLITE_OMIT_SCHEMA_PRAGMAS} {
  Defining this option omits pragmas for querying the database schema from 
  the build.
}

COMPILE_OPTION {SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS} {
  Defining this option omits pragmas for querying and modifying the 
  database schema version and user version from the build. Specifically, the 
  [schema_version] and [user_version] PRAGMAs are omitted.
}

COMPILE_OPTION {SQLITE_OMIT_SHARED_CACHE} {
  This option builds SQLite without support for shared-cache mode.
  The [sqlite3_enable_shared_cache()] is omitted along with a fair
  amount of logic within the B-Tree subsystem associated with shared
  cache management.
}

COMPILE_OPTION {SQLITE_OMIT_SUBQUERY} {
  If defined, support for sub-selects and the IN() operator are omitted.
}

COMPILE_OPTION {SQLITE_OMIT_TCL_VARIABLE} {
  If this macro is defined, then the special "$<variable-name>" syntax
  used to automatically bind SQL variables to TCL variables is omitted.
}

COMPILE_OPTION {SQLITE_OMIT_TEMPDB} {
  This option omits support for TEMP or TEMPORARY tables.
}

COMPILE_OPTION {SQLITE_OMIT_TRACE} {
  This option omits support for the [sqlite3_profile()] and
  [sqlite3_trace()] interfaces and their associated logic.
}

COMPILE_OPTION {SQLITE_OMIT_TRIGGER} {
  Defining this option omits support for TRIGGER objects. Neither the 
  [CREATE TRIGGER] or [DROP TRIGGER]
  commands are available in this case, and attempting to execute
  either will result in a parse error.
  This option also disables enforcement of [foreign key constraints],
  since the code that implements triggers and which is omitted by this
  option is also used to implement [foreign key actions].
}

COMPILE_OPTION {SQLITE_OMIT_TRUNCATE_OPTIMIZATION} {
  A default build of SQLite, if a [DELETE] statement has no WHERE clause
  and operates on a table with no triggers, an optimization occurs that
  causes the DELETE to occur by dropping and recreating the table.  
  Dropping and recreating a table is usually much faster than deleting
  the table content row by row.  This is the "truncate optimization".
}

COMPILE_OPTION {SQLITE_OMIT_UTF16} {
  This macro is used to omit support for UTF16 text encoding. When this is
  defined all API functions that return or accept UTF16 encoded text are
  unavailable. These functions can be identified by the fact that they end
  with '16', for example [sqlite3_prepare16()], [sqlite3_column_text16()] and
  [sqlite3_bind_text16()].
}

COMPILE_OPTION {SQLITE_OMIT_VACUUM} {
  When this option is defined, the [VACUUM]
  command is not included in the library.
  Executing a [VACUUM] statement causes 
  a parse error.
}

COMPILE_OPTION {SQLITE_OMIT_VIEW} {
  Defining this option omits support for VIEW objects. Neither the 
  [CREATE VIEW] nor the [DROP VIEW]
  commands are available in this case, and
  attempting to execute either will result in a parse error.

  WARNING: If this macro is defined, it will not be possible to open a database
  for which the schema contains VIEW objects. 
}

COMPILE_OPTION {SQLITE_OMIT_VIRTUALTABLE} {
  This option omits support for the [sqlite3_vtab | Virtual Table]
  mechanism in SQLite.
}

COMPILE_OPTION {SQLITE_OMIT_WAL} {
  This option omits the "[write-ahead log]" (a.k.a. "[WAL]") capability.
}

COMPILE_OPTION {SQLITE_OMIT_WSD} {
  This option builds a version of the SQLite library that contains no
  Writable Static Data (WSD).  WSD is global variables and/or static
  variables.  Some platforms do not support WSD, and this option is necessary
  in order for SQLite to work those platforms.  

  Unlike other OMIT options which make the SQLite library smaller,
  this option actually increases the size of SQLite and makes it run
  a little slower.  Only use this option if SQLite is being built for an
  embedded target that does not support WSD.
}

COMPILE_OPTION {SQLITE_OMIT_XFER_OPT} {
  This option omits support for optimizations that help statements
  of the form "INSERT INTO ... SELECT ..." run faster.
}

COMPILE_OPTION {SQLITE_UNTESTABLE} {
  A standard SQLite build includes a small amount of logic associated
  with [sqlite3_test_control()] to exercise
  parts of the SQLite core that are otherwise difficult to validate.
  This compile-time option omits that extra testing logic.  This
  compile-time option was called "SQLITE_OMIT_BUILTIN_TEST" prior
  to SQLite version 3.16.0 ([dateof:3.16.0]).  The name was changed
  to better describe the implications of using it.
  <p>
  Setting this compile-time option prevents SQLite from being fully
  testable.  Branch test coverage drops from 100% down to about 95%.
  <p>
  SQLite developers follow the NASA principle of
  "fly what you test and test what you fly".  This principle is violated
  if this option is enabled for delivery but disabled for testing.
  But if this option is enabled during testing, not all branches are 
  reachable.  Therefore, the use of this compile-time option is discouraged.
}

COMPILE_OPTION {SQLITE_ZERO_MALLOC} {
  This option omits both the [default memory allocator] and the
  [debugging memory allocator] from the build and substitutes a stub
  memory allocator that always fails.  SQLite will not run with this
  stub memory allocator since it will be unable to allocate memory.  But
  this stub can be replaced at start-time using
  [sqlite3_config]([SQLITE_CONFIG_MALLOC],...) or
  [sqlite3_config]([SQLITE_CONFIG_HEAP],...).
  So the net effect of this compile-time option is that it allows SQLite
  to be compiled and linked against a system library that does not support
  malloc(), free(), and/or realloc().
}

</tcl>
<a name="debugoptions"></a>
<h1> Analysis and Debugging Options</h1>
<tcl>

COMPILE_OPTION {SQLITE_DEBUG} {
  The SQLite source code contains literally thousands of assert() statements
  used to verify internal assumptions and subroutine preconditions and
  postconditions.  These assert() statements are normally turned off
  (they generate no code) since turning them on makes SQLite run approximately
  three times slower.  But for testing and analysis, it is useful to turn
  the assert() statements on.  The SQLITE_DEBUG compile-time option does this.
  <p>SQLITE_DEBUG also enables some other debugging features, such as
  special [PRAGMA] statements that turn on tracing and listing features
  used for troubleshooting and analysis of the [VDBE] and code generator.
}

COMPILE_OPTION {SQLITE_MEMDEBUG} {
  The SQLITE_MEMDEBUG option causes an instrumented 
  [debugging memory allocator]
  to be used as the default memory allocator within SQLite.  The
  instrumented memory allocator checks for misuse of dynamically allocated
  memory.  Examples of misuse include using memory after it is freed,
  writing off the ends of a memory allocation, freeing memory not previously
  obtained from the memory allocator, or failing to initialize newly
  allocated memory.
}

</tcl>
<a name="win32options"></a>
<h1> Windows-Specific Options</h1>
<tcl>

COMPILE_OPTION {SQLITE_WIN32_HEAP_CREATE} {
  This option forces the Win32 native memory allocator, when enabled, to
  create a private heap to hold all memory allocations.
}

COMPILE_OPTION {SQLITE_WIN32_MALLOC_VALIDATE} {
  This option forces the Win32 native memory allocator, when enabled, to
  make strategic calls into the HeapValidate() function if assert() is also
  enabled.
}

</tcl>
<a name="linkage"></a>
<h1>Compiler Linkage Control</h1>

<p>The following macros specify
interface linkage for certain kinds of SQLite builds.  The Makefiles will normally
handle setting these macros automatically.  Application developers should
not need to worry with these macros.  The following documentation about these 
macros is included completeness.</p>

<tcl>
COMPILE_OPTION {SQLITE_API} {
  This macro identifies a externally visible interface for SQLite.
  This macro is sometimes set to "extern".  But the definition is
  compiler-specific.
}

COMPILE_OPTION {SQLITE_APICALL} {
  This macro identifies the calling convention used by public interface
  routines in SQLite.  This macro is normally defined to be nothing,
  though on Windows builds it can sometimes be set to "__cdecl" or "__stdcall".
  The "__cdecl" setting is the default, but "__stdcall" is used when SQLite
  is intended to be compiled as a Windows system library.
  <p>
  A single function declaration should contain no more than one of
  the following:  [SQLITE_APICALL], [SQLITE_CALLBACK], [SQLITE_CDECL],
  or [SQLITE_SYSCALL].
}

COMPILE_OPTION {SQLITE_CALLBACK} {
  This macro specifies the calling convention used by callback pointers
  in SQLite.  This macro is normally defined to be nothing, though on Windows
  builds it can sometimes be set to "__cdecl" or "__stdcall".  The
  "__cdecl" setting is the default, but "__stdcall" is used when SQLite
  is intended to be compiled as a Windows system library.
  <p>
  A single function declaration should contain no more than one of
  the following:  [SQLITE_APICALL], [SQLITE_CALLBACK], [SQLITE_CDECL],
  or [SQLITE_SYSCALL].
}

COMPILE_OPTION {SQLITE_CDECL} {
  This macro specifies the calling convention used by varargs interface
  routines in SQLite.  This macro is normally defined to be nothing,
  though on Windows builds it can sometimes be set to "__cdecl".  This
  macro is used on varargs routines and so cannot be set to "__stdcall"
  since the __stdcall calling convention does not support varargs functions.
  <p>
  A single function declaration should contain no more than one of
  the following:  [SQLITE_APICALL], [SQLITE_CALLBACK], [SQLITE_CDECL],
  or [SQLITE_SYSCALL].
}

COMPILE_OPTION {SQLITE_SYSCALL} {
  This macro identifies the calling convention used by operating system
  interfaces for target the platform for an SQLite build.
  This macro is normally defined to be nothing, though on Windows
  builds it can sometimes be set to "__stdcall".
  <p>
  A single function declaration should contain no more than one of
  the following:  [SQLITE_APICALL], [SQLITE_CALLBACK], [SQLITE_CDECL],
  or [SQLITE_SYSCALL].
}

COMPILE_OPTION {SQLITE_TCLAPI} {
  This macro specifies the calling convention used by the 
  [http://www.tcl.tk | TCL] library interface routines.
  This macro is not used by the SQLite core, but only by the [TCL Interface]
  and [TCL test suite].
  This macro is normally defined to be nothing,
  though on Windows builds it can sometimes be set to "__cdecl".  This
  macro is used on TCL library interface routines which are always compiled
  as __cdecl, even on platforms that prefer to use __stdcall, so this
  macro should not be set to __stdcall unless the platform as a custom
  TCL library build that supports __stdcall.
  <p>
  This macro may not be used in combination with any of [SQLITE_APICALL],
  [SQLITE_CALLBACK], [SQLITE_CDECL], or [SQLITE_SYSCALL].
}


</tcl>