今天通過Ubuntu18.04.1安裝基於gcc的objective-c編譯環境,出現了一個問題,找不到objective相關的文件符號。
HelloWorld.m源碼如下
int main(int argc, const char* argv[]) {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSLog(@"hello world");
[pool drain];
return 0;
}
編譯命令:
$ gcc `gnustep-config --objc-flags` -lobjc -lgnustep-base HelloWord.m -o hello.o
出錯如下錯誤信息:
/tmp/cch0DQEt.o: In function `main':
/home/XX/ios-projects/objective-c-demo/HelloWord.m:4: undefined reference to `objc_get_class'
/home/XX/ios-projects/objective-c-demo/HelloWord.m:4: undefined reference to `objc_msg_lookup'
/home/XX/ios-projects/objective-c-demo/HelloWord.m:4: undefined reference to `objc_msg_lookup'
/home/XX/ios-projects/objective-c-demo/HelloWord.m:6: undefined reference to `NSLog'
/home/XX/ios-projects/objective-c-demo/HelloWord.m:7: undefined reference to `objc_msg_lookup'
/tmp/cch0DQEt.o: In function `__objc_gnu_init':
/home/XX/ios-projects/objective-c-demo/HelloWord.m:9: undefined reference to `__objc_exec_class'
/tmp/cch0DQEt.o:(.data.rel+0x0): undefined reference to `__objc_class_name_NSConstantString'
/tmp/cch0DQEt.o:(.data.rel+0x8): undefined reference to `__objc_class_name_NSAutoreleasePool'
collect2: error: ld returned 1 exit status
一開始還以爲是環境問題,重啓系統也沒有用,照着網上教程安裝後敲命令也不行。
折騰了一個小時以後,終於翻到了stackflow的一個答案,需要增加參數-Wl,--no-as-needed,原因是在編譯鏈接階段,由於HelloWorld.m在命令行的後面,導致前面沒有發現對應的文件符號,進而失敗。
原文如下:
https://stackoverflow.com/questions/11425120/objective-c-on-linux-compile-error
於是調整編譯命令:
$ gcc `gnustep-config --objc-flags` -Wl,--no-as-needed -lobjc -lgnustep-base HelloWord.m -o hello.o