xcode - 来自链接器的奇怪警告(ld)

Question

我们正在构建一个 Mac OSX 应用程序，该应用程序主要是用 Obj-C/Cocoa 编写的。 然后，该应用程序静态链接到一些用 C/C++ 编写并由我们编译的第三方库(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)。

应用程序运行完美，但在编译时我们总是收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。我们正在链接这些库:

1. libphonenumber ，这显然是导致 5 个警告中的 4 个的原因。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. Protocol Buffers ，通过“./configure && make”编译。

请注意:

1. 尽管有警告，应用程序仍然运行良好，但我们希望摆脱它们，因为它们很烦人。
2. xcode with boost : linker(Id) Warning about visibility settings提出的解决方案不起作用:“默认隐藏符号”始终为"is"。

Answer 1

The solution proposed by xcode with boost : linker(Id) Warning about visibility settings doesn't work: "Symbols hidden by default" has always been "YES".

这与设置为“YES”关系不大，而与在所有项目中设置为相同值关系更大。依赖于其他库的库/项目需要有一个类似的“默认隐藏符号”设置，以便正确链接并且没有错误/警告。

我以前遇到过这个问题，对所有项目的 Xcode 进行简单更改以确保设置匹配通常可以解决问题。由于听起来您也在命令行上进行编译，因此您需要查看 gcc 的 -fvisibility 参数。