g ++编译错误：对存在的共享库函数的未定义引用 [英] g++ compile error: undefined reference to a shared library function which exists

问题描述

我最近在ubuntu机器上安装了 hdf5 库，现在无法链接到导出的函数。我写了一个简单的测试脚本 readHDF.cpp 来解释问题：

  #include  $ b int main（int argc，char * argv []）
 {
 hid_t h5_file_id = H5Fopen（argv [1]，H5F_ACC_RDWR，H5P_DEFAULT）; 
返回0; 
} 
  

编译命令是

  g ++ -Wl，-rpath，$ HOME / hdf5 / lib -I $ HOME / hdf5 / include \ 
 -L ​​$ HOME / hdf5 / lib -l： $ HOME / hdf5 / lib / libhdf5.so readHDF.cpp 
  

返回以下错误

  /tmp/cc6DXdxV.o：函数`main'：
 readHDF.cpp :(。text + 0x1f）：undefined引用'H5check_version'
 readHDF.cpp :(。text + 0x3c）：对'H5Fopen'的未定义引用
 collect2：ld返回1退出状态
  

我很困惑，因为 nm 命令似乎表示该函数已被导出：

  nm -C $ HOME / hdf5 / lib / libhdf5.so | grep H5check_version 
  

返回

  0000000000034349 T H5check_version 
  

以及类似的结果 H5Fopen 。任何想法可能会出错？不知道它是否有帮助，但是如果我注释掉脚本中的 H5Fopen 部分，那么它会编译好：

  #include< hdf5.h> 
 $ b int main（int argc，char * argv []）
 {
 hid_t h5_file_id; // = H5Fopen（argv [1]，H5F_ACC_RDWR，H5P_DEFAULT）; 
返回0; 
} 
  

另外，服务器上安装了多个版本的hdf5， python模块（如h5py和tables），但是我无法让它们工作，所以我在我的本地目录中安装了这个版本，并更改​​了g ++链接器的rpath选项。

解决方案

好的，解决了。问题在于在编译命令中放置-lhdf5。显然-lhdf5应该放在readHDF.cpp之后。例如 g ++ -Wl，-rpath = $ HOME / hdf5 / lib -L ​​$ HOME / hdf5 / lib -I $ HOME / hdf5 / include readHDF.cpp -lhdf5 will编译没有问题，但 g ++ -Wl，-rpath = $ HOME / hdf5 / lib -L ​​$ HOME / hdf5 / lib -I $ HOME / hdf5 / include -lhdf5 readHDF.cpp 会因未定义的参考错误而失败。有趣的是，这只是Ubuntu 12.04的一个问题，因为两个编译命令都适用于Ubuntu 10.04。

在这篇文章中找到解释的答案：

即使nm指示此符号存在，也是未定义的符号引用。

我想在剧本安全练习后放置-lXXX。

I recently installed the hdf5 library on an ubuntu machine, and am now having trouble linking to the exported functions. I wrote a simple test script readHDF.cpp to explain the issue:

#include <hdf5.h>

int main(int argc, char * argv[])
{
  hid_t     h5_file_id = H5Fopen(argv[1], H5F_ACC_RDWR, H5P_DEFAULT);
  return 0;
}

The compile command is

g++ -Wl,-rpath,$HOME/hdf5/lib -I$HOME/hdf5/include \
    -L$HOME/hdf5/lib -l:$HOME/hdf5/lib/libhdf5.so readHDF.cpp

which returns the following error

/tmp/cc6DXdxV.o: In function `main':  
readHDF.cpp:(.text+0x1f): undefined reference to `H5check_version'  
readHDF.cpp:(.text+0x3c): undefined reference to `H5Fopen'  
collect2: ld returned 1 exit status

I am confused because the nm command seems to say that the function has been exported:

nm -C $HOME/hdf5/lib/libhdf5.so | grep H5check_version

which returns

0000000000034349 T H5check_version

and a similar result for H5Fopen. Any thoughts on what might be going wrong? Not sure if it helps, but if I comment out the H5Fopen portion of the script, then it compiles fine:

#include <hdf5.h>

int main(int argc, char * argv[])
{
hid_t     h5_file_id;// = H5Fopen(argv[1], H5F_ACC_RDWR, H5P_DEFAULT);
return 0;
}

Also there are multiple versions of hdf5 installed on the server which are used by various python modules such as h5py and tables, but I couldn't get any of them to work, so I installed this version in my local directory and changed the rpath options for g++ linker.

解决方案

Ok, solved. The issue was in the placement of the -lhdf5 in the compile command. Apparently -lhdf5 should be placed after readHDF.cpp. For instance g++ -Wl,-rpath=$HOME/hdf5/lib -L$HOME/hdf5/lib -I$HOME/hdf5/include readHDF.cpp -lhdf5 will compile with no problems, but g++ -Wl,-rpath=$HOME/hdf5/lib -L$HOME/hdf5/lib -I$HOME/hdf5/include -lhdf5 readHDF.cpp will fail with the undefined reference errors. Interestingly, this was only a problem for Ubuntu 12.04, as both compile commands worked for Ubuntu 10.04.

Found the answer with explanation at this post:

undefined reference to symbol even when nm indicates that this symbol is present

I guess placing -lXXX after the script is safer practice.

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