[sqlite3] Explicitly initialise and shut down sqlite3

[erlend-aasland]

BPO	43505
Nosy	@berkerpeksag, @serhiy-storchaka, @erlend-aasland
PRs	bpo-43505: explicitly initialise and shutdown sqlite3 #25404

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-04-14.14:51:02.925>
created_at = <Date 2021-03-15.23:09:44.794>
labels = ['type-feature', 'library', '3.10']
title = '[sqlite3] Explicitly initialise and shut down sqlite3'
updated_at = <Date 2021-04-14.15:00:17.095>
user = 'https://github.com/erlend-aasland'

bugs.python.org fields:

activity = <Date 2021-04-14.15:00:17.095>
actor = 'erlendaasland'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-14.14:51:02.925>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2021-03-15.23:09:44.794>
creator = 'erlendaasland'
dependencies = []
files = []
hgrepos = []
issue_num = 43505
keywords = ['patch']
message_count = 4.0
messages = ['388788', '391083', '391084', '391085']
nosy_count = 3.0
nosy_names = ['berker.peksag', 'serhiy.storchaka', 'erlendaasland']
pr_nums = ['25404']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43505'
versions = ['Python 3.10']

[erlend-aasland]

We should explicitly initialise (and shut down) the SQLite library in the sqlite3 module. This may be required in future releases:

Quoting from the SQLite docs:
"For maximum portability, it is recommended that applications always invoke sqlite3_initialize() directly prior to using any other SQLite interface. Future releases of SQLite may require this. In other words, the behavior exhibited when SQLite is compiled with SQLITE_OMIT_AUTOINIT might become the default behavior in some future release of SQLite."

Ref.

• https://sqlite.org/c3ref/initialize.html
• https://sqlite.org/compile.html#omit_autoinit

[berkerpeksag]

Making SQLITE_OMIT_AUTOINIT the default behavior would pretty much break every application that use SQLite, but since the PR is small enough and uses the interface in the correct way, I don't see a strong reason to reject it.

[berkerpeksag]

New changeset def9193 by Erlend Egeberg Aasland in branch 'master':
bpo-43505: Explicitly initialize and shutdown sqlite3 (GH-25404)
def9193

[erlend-aasland]

Making SQLITE_OMIT_AUTOINIT the default behavior would pretty much break every application that use SQLite [...]

Yeah, I know, _but_ if some user decides use a SQLite library compiled with SQLITE_OMIT_AUTOINIT (because it is mentioned in the "Recommended Compile-time Optinos"[1]), Python 3.10 won't break :)

[1] https://sqlite.org/compile.html

[sedoy107]

While using sqlite3 module as a part of python application, what is the right way now to call sqlite3_config given it must be called prior to sqlite3_initialize?

Below is a simplified version of code my application uses:

`

import sqlite3 # sqlite3 module in me app has already been called somewhere above by coverage module
from ctypes import *
from ctypes.util import *
libpath = find_library('sqlite3')
_sqlite3 = CDLL(libpath)
_sqlite3_config = _sqlite3.sqlite3_config
_sqlite3_config.argtypes = [c_int]
_sqlite3_config.restype = c_int
ret = _sqlite3_config(16) # ret will be eqqual 21 <----- SQLITE_MISUSE
`

My actual application uses coverage module (during unit tests). It creates separate python processes where each
imports sqlite3 executing application code. Hence SQLITE_MISUSE is issued.

Calling _sqlite3.sqlite3_shutdown() prior calling sqlite3_config seems like a viable solution in my case but I wonder if there is a better, not a hacky way. Thanks

[erlend-aasland]

While using sqlite3 module as a part of python application, what is the right way now to call sqlite3_config given it must be called prior to sqlite3_initialize?

You need to call sqlite3_config before importing the sqlite3 extension module.