GCC和ld找不到导出的符号...但他们在那里！ [英] GCC and ld can't find exported symbols...but they're there!

问题描述

我有一个C ++库和一个C ++应用程序，试图使用从库中导出的函数和类。该库建立良好，应用程序编译但无法链接。我得到的错误信息如下：

app-source-file.cpp :( .text + 0x2fdb）：未定义的引用-namespace :: GetStatusStr（int）'

库中的类似乎被链接器解析得很好，但是自由函数和导出的数据（如余弦查找表）总是会导致上述错误。

我使用的是Ubuntu 8.04（Hardy），它与最新的Unbuntu

链接库的命令是（除去其他库）：

  g ++ -fPIC -Wall -O3 -shared -Wl，-soname，lib-in-question.so -o〜/ project / lib / release / lib-in-question.so 
  code> 

链接应用程序的命令是（除去其他库）：



  g ++ -fPIC -Wall -O3 -L〜/ project / lib / release -llib-in-question -o〜/ project / release / app-in-question 
  

最后，它显示（最好像I ca n告诉）有问题的符号正在被正确导出：

  nm -D〜/ project / lib / release / lib- |问题grep GetStatusStr  - > U _ZN3lib-namespace12GetStatusStrEi 
  




解决方案

_ZN3lib-namespace12GetStatusStrEi nm输出显示库中的符号未定义。

也许它是在错误的名称空间中定义的：它看起来像是在调用它在lib-namepace中，但你可能会在另一个中定义它。

I have a C++ library and a C++ application trying to use functions and classes exported from the library. The library builds fine and the application compiles but fails to link. The errors I get follow this form:

app-source-file.cpp:(.text+0x2fdb): undefined reference to `lib-namespace::GetStatusStr(int)'

Classes in the library seem to be resolved just fine by the linker, but free functions and exported data (like a cosine lookup table) invariably result in the above error.

I am using Ubuntu 8.04 (Hardy), and it is up to date with the latest Unbuntu packages.

The command to link the library is (with other libraries removed):

g++ -fPIC -Wall -O3 -shared -Wl,-soname,lib-in-question.so -o ~/project/lib/release/lib-in-question.so

The command to link the application is (with other libraries removed):

g++ -fPIC -Wall -O3  -L~/project/lib/release -llib-in-question -o ~/project/release/app-in-question

Finally, it appears (as best as I can tell) that the symbols in question are being exported properly:

nm -D ~/project/lib/release/lib-in-question.so | grep GetStatusStr --> U _ZN3lib-namespace12GetStatusStrEi

解决方案

the U before _ZN3lib-namespace12GetStatusStrEi in the nm output shows that the symbol is undefined in the library.

Maybe it's defined in the wrong namespace: it looks like you're calling it in lib-namepace but you might be defining it in another.

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