Plug-in built with Xcode 11 fails to load on Yosemite (10.10)

MacOSX and iOS
32

Here’s a very simple app that won’t run on 10.10 when built with the 10.15 SDK:

main.m

#import <Foundation/Foundation.h>
#import <AudioToolbox/AudioToolbox.h>

int main(int argc, const char * argv[]) {
    AudioComponent comp = NULL;

    for (;;) {
        AudioComponentDescription desc;
        memset((void*)&desc, 0, sizeof(desc));

        comp = AudioComponentFindNext(comp, &desc);
        if (comp == NULL)
            break;

        if (AudioComponentGetDescription(comp, &desc) != noErr)
            continue;

        CFStringRef cfName;
        if (AudioComponentCopyName(comp, &cfName) == noErr) {
            NSLog(@"%@", (__bridge NSString*)cfName);
            CFRelease(cfName);
        }
    }

    return 0;
}

The runtime error message is:

dyld: lazy symbol binding failed: Symbol not found: _AudioComponentFindNext
  Referenced from: /Users/tom/workspace/./AUScan
  Expected in: /System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox

dyld: Symbol not found: _AudioComponentFindNext
  Referenced from: /Users/tom/workspace/./AUScan
  Expected in: /System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox

Trace/BPT trap: 5

So it looks like there’s a mismatch between what’s present on 10.10 and what the 10.15 SDK is expecting. Running nm on /System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox on the 10.10 machine gives us

000000000000e89e T __AT_AudioComponentFindNext

If we look at the contents of MacOSX10.14.sdk/System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox.tbd then we will find an entry for _AudioComponentFindNext in the list of symbols for /System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox.

However, if we look at what’s inside MacOSX10.15.sdk/System/Library/Frameworks/AudioToolbox.framework/Versions/A/AudioToolbox.tbd then the only _AudioComponentFindNext entry is in the listings for /System/Library/PrivateFrameworks/AudioToolboxCore.framework/Versions/A/AudioToolboxCore.

I’ve not quite got the full picture, but it suggests that the location of the symbol has changed in the latest SDK and it’s broken backwards compatibility.

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