Repository navigation
Compile with Pdo\Sqlite::loadExtension() by default? #17251
Description
Description
Apologies if this isn't the right place to ask a question like this, but am I understanding correctly that compiling PHP with PDO_SQLITE_OMIT_LOAD_EXTENSION=0 adds a loadExtension() method to PDO\Sqlite, letting developers load SQLite extensions?
(Added in #12804)
See:
php-src/ext/pdo_sqlite/config.m4
Line 28 in 4e9cde7
php-src/ext/pdo_sqlite/pdo_sqlite.c
Lines 69 to 71 in 4e9cde7
I'm curious why this is omitted by default. The RFC clarifies that the approach used in the PR above only allows loading extensions using the C API, not SQLite statements, so there shouldn't be any risks?
Is it because the sqlite library on the server may be compiled with SQLITE_OMIT_LOAD_EXTENSION and the method has no way of knowing that?
Being able to load SQLite extensions in PDO, without recompiling PHP, would be very helpful imo since there's a decent number of questions online asking how to achieve certain things with PDO (which is often a requirement e.g. in Laravel's ORM) vs the SQLite3 class directly.
Activity
SakiTakamachi commentedon Dec 24, 2024
@kocsismate
Can you look it?
cmb69 commentedon Dec 24, 2024
If SQLite3 doesn't have
sqlite3_load_extension(),PDO_SQLITE_OMIT_LOAD_EXTENSIONis defined (to 1), and thenPdo\Sqlite::loadExtension()is not available. If you use an SQLite3 which hassqlite3_load_extension(), the PHP method is available.stancl commentedon Dec 24, 2024
@cmb69 Wouldn't that check be running in the environment compiling the PHP build, not necessarily the environment running it? Not sure how you approach these things, but since most people install pre-built PHP, the environment compiling it shouldn't necessarily mean much here I think?
I'm mainly wondering if there could be a runtime check in
Pdo\Sqlite::loadExtension()rather than a compile time check essentially.kocsismate commentedon Dec 24, 2024
@stancl Yes, the check runs during compile time.
The only thing we could do in this case is to trigger an exception during run-time if the necessary dependency (
sqlite3_load_extension()) is not available. So I guess the best course of action would be to ask packagers to allow this sqlite3 function in their build.cmb69 commentedon Dec 24, 2024
Can we? Sure, we could use runtime linkinkg (use
dlopen()and friends) to check whether the symbol is available, but I wouldn't go down that path. And actually, we're doing similar compile-time checks for a lot of dependency libraries. Plus, SQLite3 supports theload_extension()SQL function, which might be usable.stancl commentedon Dec 25, 2024
Sorry if this is a dumb question, but does
sqlite3_load_extensionhave to be available for the compilation to work at all, or does compilation work regardless and it's just that the compilation step tries to make the PHP functionality match the linked sqlite library?If it's the latter, I wonder if there really is value in conditional compilation. If I can download a binary compiled for sqlite with
sqlite3_load_extensionbut I don't have it in my local sqlite, I'll just get an exception. If I download a binary compiled for sqlite WITHOUT that feature and I do have it in my sqlite, I'll miss out on functionality just because of what the packager's environment was.Runtime exceptions that decouple the compilation environment from the runtime environment would make more sense to me, though again it's very possible I'm missing something.
cmb69 commentedon Dec 26, 2024
It's not so much about compilation, but about the linking. If you use a function, during linking the linker will complain that the function is not defined. If you run against a shared library, you could use runtime linking, which avoids the problem that the linker complains, but that is somewhat brittle, and won't work if php_sqlite3/php_pdo_sqlite are build against a static libsqlite3.
stancl commentedon Dec 26, 2024
Ah I see, didn't realize it wasn't being linked at runtime. So I'm guessing if the compilation environment doesn't match the actual runtime environment, that's just kind of unfortunate but a problem of the person using the pre-built version? Meaning if they have a somewhat nonstandard setup, it's best if they just compile PHP themselves?
cmb69 commentedon Dec 26, 2024
Right. That's always an option. :)
stancl commentedon Dec 31, 2024
I've realized the source of my confusion here. The fact that libsqlite3 is linked statically means the user's SQLite setup is actually irrelevant, so this is just about packagers choosing to build PHP with or without certain SQLite features. But PHP and the relevant libsqlite should always be in sync then.
Thanks for the clarification.