When I try to build a project with Xcode 12 Beta 4 to test iOS14, I got a plenty of Undefined symbols for architecture x86_64. Every time I build the app, the list of errors is changed. Native libraries fail to recognize base React classes.
Code Block Undefined symbols for architecture x86_64: "_RCTMakeAndLogError", referenced from: _RCTErrorForKey in RNCAsyncStorage.o -[RNCAsyncStorage _writeEntry:changedManifest:] in RNCAsyncStorage.o "_RCTJSErrorFromNSError", referenced from: -[RNCAsyncStorage multiMerge:callback:] in RNCAsyncStorage.o "_RCTJSONStringify", referenced from: -[RNCAsyncStorage _writeManifest:] in RNCAsyncStorage.o -[RNCAsyncStorage multiMerge:callback:] in RNCAsyncStorage.o "_RCTCurrentThreadName", referenced from: -[RNCAsyncStorage _ensureSetup] in RNCAsyncStorage.o "_RCTJSONParse", referenced from: -[RNCAsyncStorage multiMerge:callback:] in RNCAsyncStorage.o "RCTAssertFormat", referenced from: -[RNCAsyncStorage _ensureSetup] in RNCAsyncStorage.o "_RCTMD5Hash", referenced from: -[RNCAsyncStorage _filePathForKey:] in RNCAsyncStorage.o "RCTLogNativeInternal", referenced from: -[RNCAsyncStorage _ensureSetup] in RNCAsyncStorage.o _RCTStorageDirectoryMigrationLogError in RNCAsyncStorage.o "_RCTMakeError", referenced from: -[RNCAsyncStorage _ensureSetup] in RNCAsyncStorage.o _RCTReadFile in RNCAsyncStorage.o -[RNCAsyncStorage _writeManifest:] in RNCAsyncStorage.o -[RNCAsyncStorage _writeEntry:changedManifest:] in RNCAsyncStorage.o _37-[RNCAsyncStorage multiGet:callback:]_block_invoke_2 in RNCAsyncStorage.o _RCTMakeErrors in RNCAsyncStorage.o _25-[RNCAsyncStorage clear:]_block_invoke in RNCAsyncStorage.o ... "_RCTJSONParseMutable", referenced from: -[RNCAsyncStorage _ensureSetup] in RNCAsyncStorage.o -[RNCAsyncStorage multiMerge:callback:] in RNCAsyncStorage.o "_RCTRegisterModule", referenced from: +[RNCAsyncStorage load] in RNCAsyncStorage.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)
I opened a issue in React-Native repository: https://github.com/facebook/react-native/issues/29633
A sample project with the error happening: https://github.com/igoriols/xcode12reactnativesample