c++ runtime "symbol lookup error"

短命女 2022-08-06 11:17 14阅读 0赞

**c++ runtime "symbol lookup error"**

I was working on a c++ project. Everything linked and compiled fine. Upon running the executable, I got the following error:

> ./ TestCppProgram: symbol  lookup error: ./ TestCppProgram: undefined symbol: \_ZN12 CppProgramC1Ev

I searched the  internet . Two of the interesting links I found were the following:

*  http://osdir.com/ml/gcc.g++.general/2005-02/msg00061.html
 *  http://www.linuxquestions.org/questions/linux-software-2/undefined-symbol-cout-263568/

For me it ended up being a bad  LD \_LIBRARY\_PATH. The path I intended the executable to find it's needed shared library was in the LD \_LIBRARY\_PATH, it just wasn't before a different path which had an older version of the needed shared library. (This happened to me when I updated by  bashrc  with a library path and just re-sourced it).  
  
Some cool commands in the debugging process:

*  ldd TestCppProgram (Shows you where your program is getting it's libraries from. An early-on careful inspection of this would've quickly let me to my problem!)
 *  ldd -d -r TestCppProgram (Shows you any undefined symbols. There shouldn't be any undefined symbols for an executable, but there will be for a shared lib if it depends on another shared lib. Somebody please correct me if I'm wrong)
 *  nm TestCppProgram | c++filt (displays unmangled symbol information)  
    
 *  nm TestCppProgram (Displays mangled symbol information. Ie: You should be able to find stuff like ZN12CppProgramC1Ev in here. In my problem above, I found which line number the undefined symbol in question was on, and then looked it up in the unmangled version to see what function it was trying to resolve. It let me know, but it didn't really help me find out what my problem was.)
 *  readelf -d TestCppProgram (Shows library dependencies. similar to ldd.)