HOW TO sqlite3_load_extension from within Objective-c [error: dlopen(...) image not found] - objective-c

Question

I am trying to load an extension to sqlite3 for use within iPhone application objective-c code. I successfully compiled the c file of new functions into a dylib named libsqlitefunctions.dylib. Here is where I am a bit lost. I call sqlite3_load_extension as follows:
char *error = sqlite3_malloc(MAX_SQLITE_ERROR_MESSAGE_SIZE);
const char *library = [#"libsqlitefunctions.dylib" UTF8String];
if (sqlite3_load_extension(database, library, 0, &error) != SQLITE_OK) {
message = [NSString stringWithFormat:#"%s", error];
}
sqlite3_free(error);
No matter what I do, I get the error: dlopen(libsqlitefunctions.dylib, 10): image not found
I tried:
indicating the fully qualified path to the dylib
indicating a relative path
not indicating a path (as shown above)
adding the dylib as a framework
adding the .c file to my project and compiling it into a .o file and then trying to load it
Please note that this is not an entry point problem, since I pass 0 as that arg. This will force the dylib to load by calling an init function defined in the dylib. I do not even get to that point.
I am pretty much a newbie compared to the rest of you guys and feel that I am probably lacking an understanding of how libraries are loaded.
I would really appreciate any ideas since the ability to make use of the functions in this library is important to the functionality of my app. Thank you all in advance.

Answer 1

OK, I took your advice and simply added my new functionality to the sqlite3.c file I had in my project. It compiled and linked statically and works fine. Thank you for the idea. I still would like to know what was preventing me from loading an extension, but am pleased with having learned other things in solving the problem - PLUS I met my deadline. Thank you again.

Answer 2

After days of search I finally found a solution !
1) once your sqlite_extension.h and sqlite_extension.c files moved into your sqlite_extension folder
2) cd to that sqlite_extension folder
3) compile your code using :
gcc -g -fPIC -std=gnu99 -current_version 1.0 -compatibility_version 1.0 -dynamiclib -arch arm64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk -arch armv7 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk sqlite_extension.c -o sqlite_extension.dylib
You might need to change the SDK path for something like ../iPhoneOSN.M.sdk where N.M indicate the last available version of iOS, have a look to the folder "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/" to find an existing path
4) You can check the resulting file using :
file /path/to/your/sqlite_extension.dylib
which should return something like :
/./././sqlite_extension.dylib (for architecture armv7): Mach-O dynamically linked shared library arm
/./././sqlite_extension.dylib (for architecture arm64): Mach-O 64-bit dynamically linked shared library
or using the more detailed :
otool -l sqlite_extension.dylib
5) Now your library needs to be code-signed with the same identity as your embedding app you can do this using :
codesign -fs "your_apple_identity" sqlite_extension.dylib
your_apple_identity can be in the form "your_name: your_apple_login_email#address.xxx"
The best way to make sure is to copy the one from your embedded app executable compiled and running on your device with Xcode or the archive on your computer using :
codesign --display --verbose=4 ~/Library/Developer/Xcode/Archives/2016-09-25/YourApp\ 25-09-2016\ 12.00.xcarchive/Products/Applications/YourApp.app/YourApp
The string to use in place of "your_apple_identity" is the one found after the first occurence of Authority=
6) Once your library code-signed, you can check that you get similar signing information as your App using the same command :
codesign --display --verbose=4 sqlite_extension.dylib
7) Your Library is now ready to be embedded in your app, all you need is to make sure Xcode refreshes your library file if you had try a previous file with the same name. To do so you can remove the former file, compile and run on your device, put back the new file making sure it is in the "Copy Bundle ressources" not the "Link Binary With Librairies" of the Build Phases tab of your app
Your extension should then load without error when your app requests SQLite to use it
iOS 9.3.5
Xcode 8.0
SQLite 3.9.2

Answer 3

I'm not 100% sure this is explicitly disallowed, but another type of dynamic loading -- frameworks -- isn't supported on the iPhone. You may need to compile and link the library statically, rather than dynamically.

Answer 4

i know topic is old . but googling brought me here. and for anyone that has this problem and end up here :
you must first call
sqlite3_enable_load_extension(db, 1);

Answer 5

I know that I am answering late but I faced the same problem and found how to load an extension.
Once you have the source file X.c, compile a shared library(In Linux machine) using
gcc -g -fPIC -shared X.c -o X.so
Where X.c is the extension in use
Then enable loading extension in C interface to SQLite using
sqlite3_enable_load_extension(db,1);
Then load the extension using
sqlite3_load_extension(db,"/path/of/extension/X.so","sqlite3_X_init",0);
Thats it, extension will be loaded now.