From 32296ab1abd13a0dce7fd21acbe96e4fc9b9f315 Mon Sep 17 00:00:00 2001
From: "Jeremy W. Rowe" <jeremy.rowe@shopify.com>
Date: Thu, 19 Dec 2024 09:31:55 -0500
Subject: [PATCH] Removes sqlite3_config and sqlite3_initialize from local db
 new

This change removes ffi::sqlite3_config() and ffi::sqlite3_initialize()
from local/database.new and moves the configuration down to
local/connection#connect. This is done because a SQLite connection can
not be initialized multiple times, this change frees users of the
library to intialize SQLite connections at a different level. initialize
specifically presents a problem when libsql is being included in a
shared library where there are other shared libraries that interact with
the SQLite C API. This change *should* be relatively safe, since
connections can change the threading mode on a per connection basis so
long that sqlite was compiled with SQLITE_THREADSAFE=1 or
SQLITE_THREADSAFE=2.

Refs:

* https://sqlite.org/threadsafe.html
* https://sqlite.org/c3ref/c_config_covering_index_scan.html#sqliteconfigserialized.
---
 libsql/src/local/connection.rs | 16 +++++++++++++-
 libsql/src/local/database.rs   | 38 +++++++++-------------------------
 2 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/libsql/src/local/connection.rs b/libsql/src/local/connection.rs
index 56ff743ee5..5bc2a5f1ad 100644
--- a/libsql/src/local/connection.rs
+++ b/libsql/src/local/connection.rs
@@ -38,14 +38,28 @@ impl Connection {
     pub(crate) fn connect(db: &Database) -> Result<Connection> {
         let mut raw = std::ptr::null_mut();
         let db_path = db.db_path.clone();
+        let flags: c_int = ffi::SQLITE_OPEN_FULLMUTEX | db.flags.bits();
+
         let err = unsafe {
+            if ffi::sqlite3_threadsafe() == 0 {
+                // https://sqlite.org/threadsafe.html
+                return Err(Error::ConnectionFailed(String::from(
+                    "SQLite thread safety check failed: SQLite was compiled without thread-safety support \
+                    (SQLITE_THREADSAFE=0). For libsql to operate correctly, SQLite must be compiled with either \
+                    serialized mode (SQLITE_THREADSAFE=1) or multi-threaded mode (SQLITE_THREADSAFE=2). \
+                    Thread-safety is required because libsql needs to ensure safe concurrent access to database \
+                    connections across multiple threads. \
+                    Please rebuild SQLite with the appropriate thread-safety options."
+                )));
+            }
+
             ffi::sqlite3_open_v2(
                 std::ffi::CString::new(db_path.as_str())
                     .unwrap()
                     .as_c_str()
                     .as_ptr() as *const _,
                 &mut raw,
-                db.flags.bits() as c_int,
+                flags,
                 std::ptr::null(),
             )
         };
diff --git a/libsql/src/local/database.rs b/libsql/src/local/database.rs
index 726bb98a4e..ab1645804b 100644
--- a/libsql/src/local/database.rs
+++ b/libsql/src/local/database.rs
@@ -1,5 +1,3 @@
-use std::sync::Once;
-
 cfg_replication!(
     use http::uri::InvalidUri;
     use crate::database::{EncryptionConfig, FrameNo};
@@ -24,7 +22,6 @@ cfg_sync! {
 
 use crate::{database::OpenFlags, local::connection::Connection};
 use crate::{Error::ConnectionFailed, Result};
-use libsql_sys::ffi;
 
 // A libSQL database.
 pub struct Database {
@@ -230,29 +227,6 @@ impl Database {
     }
 
     pub fn new(db_path: String, flags: OpenFlags) -> Database {
-        static LIBSQL_INIT: Once = Once::new();
-
-        LIBSQL_INIT.call_once(|| {
-            // Ensure that we are configured with the correct threading model
-            // if this config is not set correctly the entire api is unsafe.
-            unsafe {
-                assert_eq!(
-                    ffi::sqlite3_config(ffi::SQLITE_CONFIG_SERIALIZED),
-                    ffi::SQLITE_OK,
-                    "libsql was configured with an incorrect threading configuration and
-                    the api is not safe to use. Please check that no multi-thread options have
-                    been set. If nothing was configured then please open an issue at:
-                    https://github.com/libsql/libsql"
-                );
-
-                assert_eq!(
-                    ffi::sqlite3_initialize(),
-                    ffi::SQLITE_OK,
-                    "libsql failed to initialize"
-                );
-            }
-        });
-
         Database {
             db_path,
             flags,
@@ -420,7 +394,11 @@ impl Database {
     }
 
     #[cfg(feature = "sync")]
-    async fn try_push(&self, sync_ctx: &mut SyncContext, conn: &Connection) -> Result<crate::database::Replicated> {
+    async fn try_push(
+        &self,
+        sync_ctx: &mut SyncContext,
+        conn: &Connection,
+    ) -> Result<crate::database::Replicated> {
         let page_size = {
             let rows = conn
                 .query("PRAGMA page_size", crate::params::Params::None)?
@@ -471,7 +449,11 @@ impl Database {
     }
 
     #[cfg(feature = "sync")]
-    async fn try_pull(&self, sync_ctx: &mut SyncContext, conn: &Connection) -> Result<crate::database::Replicated> {
+    async fn try_pull(
+        &self,
+        sync_ctx: &mut SyncContext,
+        conn: &Connection,
+    ) -> Result<crate::database::Replicated> {
         let generation = sync_ctx.generation();
         let mut frame_no = sync_ctx.durable_frame_num() + 1;
         conn.wal_insert_begin()?;