On 6 Mar 2024, at 04:02, Boris D. <borisd@gmx.com> wrote:
Hello, I am interested in interacting with the Objective-C runtime from other
languages through FFI bindings.
In particular, I need to be able to load Foundation or other classes
dynamically. What needs to be done to load these classes in the runtime? Here's
an example illustrating the issue I'm facing:
// clang `gnustep-config --objc-flags` `gnustep-config --objc-libs` simple.c -o
simple
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[])
{
Class c = objc_getClass("NSObject");
printf("Got a class: %s\n", c ? "pass" : "fail");
return 0;
}
Currently it fails.
It may not be the only problem, but you are linking your program without NSObject, so you
definitely wouldn't expect to be able to have objc_getClass("NSObject") return
it.
NSObject is implemented in the base library, so any code that wants to use it
would need to be linked with that library (see 'gnustep-config --base-libs).
I don't know if it's true nowadays, but I remember in the past the linker on
some systems wouldn't actually 'pull in' a library unless your code used a
symbol from the library, and since you are not cmpiling ObjectiveC code it
won't be using the classes in the library, so linking with the base library may
well not be enough.
If that's the case, then in theory you could use C dynamic library loading
functions to exlicitly load the base library into your running program and
register things with the runtime, but that's probably really complicated.
A simple solution would be to compile a small objective-C code fragment
eg
void setup_base()
{
[NSObject class];
}
You could then have yur C code link with that and call the setup_base()
function at the start.
That would ensure that the base library is linked into your code.
You could then use the NSBundle class to dynamically load other stuff.