Fix panic at 'SQLite API not initialized or SQLite feature omitted'

`to_sqlite_error` needs `sqlite3_malloc`

```
sqlite> .log on
sqlite> .load target/debug/examples/libloadable_extension.so
Error: error during initialization: SQLite version mismatch: 3014000 < 3042000
```

examples/loadable_extension.rs

@@ -25,7 +25,9 @@ pub extern "C" fn sqlite3_extension_init(
     pz_err_msg: *mut *mut c_char,
     p_api: *mut ffi::sqlite3_api_routines,
 ) -> c_int {
-    if let Err(err) = extension_init(db, p_api) {
+    if p_api.is_null() {
+        return ffi::SQLITE_ERROR;
+    } else if let Err(err) = extension_init(db, p_api) {
         return unsafe { to_sqlite_error(&err, pz_err_msg) };
     }
     ffi::SQLITE_OK

libsqlite3-sys/bindgen-bindings/bindgen_3.14.0_ext.rs

@@ -6267,9 +6267,7 @@ pub unsafe fn sqlite3_expanded_sql(
 pub unsafe fn rusqlite_extension_init2(
     p_api: *mut sqlite3_api_routines,
 ) -> ::std::result::Result<(), crate::InitError> {
-    if p_api.is_null() {
-        return Err(crate::InitError::NullApiPointer);
-    }
+    __SQLITE3_MALLOC.store((*p_api).malloc, ::atomic::Ordering::Release);
     if let Some(fun) = (*p_api).libversion_number {
         let version = fun();
         if SQLITE_VERSION_NUMBER > version {
@@ -6371,7 +6369,6 @@ pub unsafe fn rusqlite_extension_init2(
     __SQLITE3_LIBVERSION.store((*p_api).libversion, ::atomic::Ordering::Release);
     __SQLITE3_LIBVERSION_NUMBER
         .store((*p_api).libversion_number, ::atomic::Ordering::Release);
-    __SQLITE3_MALLOC.store((*p_api).malloc, ::atomic::Ordering::Release);
     __SQLITE3_OPEN.store((*p_api).open, ::atomic::Ordering::Release);
     __SQLITE3_OPEN16.store((*p_api).open16, ::atomic::Ordering::Release);
     __SQLITE3_PREPARE.store((*p_api).prepare, ::atomic::Ordering::Release);

libsqlite3-sys/build.rs

@@ -702,6 +702,7 @@ mod loadable_extension {
         let sqlite3_api_routines_ident = sqlite3_api_routines.ident;
         let p_api = quote::format_ident!("p_api");
         let mut stores = Vec::new();
+        let mut malloc = Vec::new();
         // (2) `#define sqlite3_xyz sqlite3_api->abc` => `pub unsafe fn
         // sqlite3_xyz(args) -> ty {...}` for each `abc` field:
         for field in sqlite3_api_routines.fields {
@@ -764,7 +765,12 @@ mod loadable_extension {
                 &syn::parse2(tokens).expect("could not parse quote output"),
             ));
             output.push('\n');
-            stores.push(quote::quote! {
+            if name == "malloc" {
+                &mut malloc
+            } else {
+                &mut stores
+            }
+            .push(quote::quote! {
                 #ptr_name.store(
                     (*#p_api).#ident,
                     ::atomic::Ordering::Release,
@@ -775,9 +781,7 @@ mod loadable_extension {
         let tokens = quote::quote! {
             /// Like SQLITE_EXTENSION_INIT2 macro
             pub unsafe fn rusqlite_extension_init2(#p_api: *mut #sqlite3_api_routines_ident) -> ::std::result::Result<(),crate::InitError> {
-                if #p_api.is_null() {
-                    return Err(crate::InitError::NullApiPointer);
-                }
+                #(#malloc)* // sqlite3_malloc needed by to_sqlite_error
                 if let Some(fun) = (*#p_api).libversion_number {
                     let version = fun();
                     if SQLITE_VERSION_NUMBER > version {

libsqlite3-sys/sqlite3/bindgen_bundled_version_ext.rs

@@ -7463,9 +7463,7 @@ pub unsafe fn sqlite3_is_interrupted(arg1: *mut sqlite3) -> ::std::os::raw::c_in
 pub unsafe fn rusqlite_extension_init2(
     p_api: *mut sqlite3_api_routines,
 ) -> ::std::result::Result<(), crate::InitError> {
-    if p_api.is_null() {
-        return Err(crate::InitError::NullApiPointer);
-    }
+    __SQLITE3_MALLOC.store((*p_api).malloc, ::atomic::Ordering::Release);
     if let Some(fun) = (*p_api).libversion_number {
         let version = fun();
         if SQLITE_VERSION_NUMBER > version {
@@ -7567,7 +7565,6 @@ pub unsafe fn rusqlite_extension_init2(
     __SQLITE3_LIBVERSION.store((*p_api).libversion, ::atomic::Ordering::Release);
     __SQLITE3_LIBVERSION_NUMBER
         .store((*p_api).libversion_number, ::atomic::Ordering::Release);
-    __SQLITE3_MALLOC.store((*p_api).malloc, ::atomic::Ordering::Release);
     __SQLITE3_OPEN.store((*p_api).open, ::atomic::Ordering::Release);
     __SQLITE3_OPEN16.store((*p_api).open16, ::atomic::Ordering::Release);
     __SQLITE3_PREPARE.store((*p_api).prepare, ::atomic::Ordering::Release);

libsqlite3-sys/src/error.rs

@@ -275,8 +275,6 @@ pub fn code_to_str(code: c_int) -> &'static str {
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 #[non_exhaustive]
 pub enum InitError {
-    /// Invalid sqlite3_api_routines pointer
-    NullApiPointer,
     /// Version mismatch between the extension and the SQLite3 library
     VersionMismatch { compile_time: i32, runtime: i32 },
     /// Invalid function pointer in one of sqlite3_api_routines fields
@@ -286,9 +284,6 @@ pub enum InitError {
 impl ::std::fmt::Display for InitError {
     fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
         match *self {
-            InitError::NullApiPointer => {
-                write!(f, "Invalid sqlite3_api_routines pointer")
-            }
             InitError::VersionMismatch {
                 compile_time,
                 runtime,