来自链接器的奇怪警告(ld)

Question

我们正在构建一个主要使用Obj-C/Cocoa编写的Mac OSX应用程序.然后,应用程序静态链接一些第三方库,用C/C++编写并由我们编译(在命令行上,使用MacPorts或通常的"./configure && make";所有都是通用二进制文件).

该应用程序运行正常,但广告编译时我们总是得到这些奇怪的链接器警告:

ld: warning: direct access in ___cxx_global_var_init17 to global weak symbol __ZGVN4i18n12phonenumbers9SingletonINS0_15PhoneNumberUtilEE8instanceE means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings.
ld: warning: direct access in ___cxx_global_var_init17 to global weak symbol __ZGVN4i18n12phonenumbers9SingletonINS0_15PhoneNumberUtilEE8instanceE means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings.
ld: warning: direct access in ___cxx_global_var_init17 to global weak symbol __ZN5boost10scoped_ptrIN4i18n12phonenumbers15PhoneNumberUtilEED1Ev means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings.
ld: warning: direct access in ___cxx_global_var_init17 to global weak symbol __ZN4i18n12phonenumbers9SingletonINS0_15PhoneNumberUtilEE8instanceE means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings.
ld: warning: direct access in ___cxx_global_var_init17 to global weak symbol __ZGVN4i18n12phonenumbers9SingletonINS0_15PhoneNumberUtilEE8instanceE means the weak symbol cannot be overridden at runtime. This was likely caused by different translation units being compiled with different visibility settings.

这来自C/C++库.我们正在与这些库链接:

1. libphonenumber,显然是5个警告中的4个.由我们通过"cmake"编译.
2. boost(libboost_thread-mt),负责1个警告.使用MacPorts编译.
3. ICU(libicudata,libicuuc,libicui18n),使用MacPorts编译.
4. 协议缓冲区,通过"./configure && make"编译.

请注意:

1. 尽管有警告,应用程序仍然完美运行,但我们想摆脱它们,因为它们很烦人.
2. xcode提出的解决方案使用boost:链接器(Id)关于可见性设置的警告不起作用:"默认情况下隐藏的符号"始终为"YES".

Answer 1

xcode提出的解决方案使用boost:链接器(Id)关于可见性设置的警告不起作用:"默认情况下隐藏的符号"始终为"YES".

这与设置为"YES"的关系较少,更多的是与在所有项目中设置为相同的值有关.依赖于其他库的库/项目需要具有"默认隐藏的符号"的类似设置,以便正确链接并且没有错误/警告.

我之前遇到过这种情况,并且对所有项目进行Xcode的简单更改以确保设置匹配通常可以解决问题.既然听起来你也在编译命令行,那么你需要注意的是-fvisibility参数gcc.

Answer 2

TL:博士; -fvisibility=hidden在编译的所有内容中使用gcc和llvm编译器开关,包括依赖库,除非你有理由不这样做.

在撰写本文时,Apple网站上提供了对-fvisibility和-fvisibility-inline-hidden编译标志的良好介绍.本文还详细介绍了声明__attribute__((visibility("hidden")))和__attribute__((visibility("default")))声明.

Answer 3

通过放入-fvisibility=hidden -fvisibility-inlines-hiddenOTHER C++ FLAGS，我在 Xcode 中得到了警告。