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I'm trying to use the JsonCpp library. I'm on Windows, using MinGW and CodeBlocks.

When I include anything from the json headers, my linker implodes and gives out this two errors. I've started to look around and I found these two other questions which basically describe my problem:

problem with g++ and "undefined reference to `__gxx_personality_v0'"

What is __gxx_personality_v0 for?

And if I declare the two missing variables as void pointers, like below, the problem goes away:

void * __gxx_personality_v0=0;
void * _Unwind_Resume =0;

However, I don't understand why this error happens. CodeBlocks is set up so that it uses migw32-g++ for cpp files, and also adding the -lstdc++ option does not fix the problem. Neither does the option -fno-exception ( I want exceptions, mind you, I was just trying ).

I'm also including a boost library in the same file and that does not cause any problems.

EDIT:

The error output is exactly what I said in my title: I get a total of 22 undefined references to _Unwind_Resume and __gxx_personality_v0 during the linking. My code is:

#include <boost/algorithm/string.hpp>
#include <include/json/value.h>
//void * __gxx_personality_v0=0;
//void * _Unwind_Resume =0;
int main () {
    std::string str1("Hello world!");
    boost::to_upper(str1);
    Json::Value k;
    return 0;
}

The error is there only when I include/use the JsonCPP library. Uncommenting the commented lines fixes the problem.

The command line output is this:

mingw32-g++.exe -Wall -fexceptions  -g  -DSFML_DYNAMIC   -IC:\Users\Svalorzen\Documents\Projects\boost_1_49 -IC:\Users\Svalorzen\Documents\Projects\jsoncpp-src-0.5.0 -IC:\Users\Svalorzen\Documents\Projects\SFML-1.6\include -IC:\Users\Svalorzen\Documents\Projects\hge181\include  -c C:\Users\Svalorzen\Documents\Projects\test\main.cpp -o obj\Debug\main.o
mingw32-g++.exe -LC:\Users\Svalorzen\Documents\Projects\jsoncpp-src-0.5.0 -LC:\Users\Svalorzen\Documents\Projects\SFML-1.6\lib -LC:\Users\Svalorzen\Documents\Projects\hge181\lib  -o bin\Debug\test.exe obj\Debug\main.o   -fno-exceptions -lsfml-graphics -lsfml-window -lsfml-system  C:\Users\Svalorzen\Documents\Projects\jsoncpp-src-0.5.0\libs\mingw\libjson_mingw_libmt.a C:\Users\Svalorzen\Documents\Projects\hge181\lib\gcc\libhge.a C:\Users\Svalorzen\Documents\Projects\hge181\lib\gcc\libhelp.a 
Output size is 1.22 MB
Process terminated with status 0 (0 minutes, 3 seconds)
0 errors, 0 warnings

SECOND EDIT: I'm adding the command lines I use to compile the library:

g++ -o buildscons\mingw\src\lib_json\json_reader.o -c -DWIN32 -DNDEBUG -D_MT -Iinclude src\lib_json\json_reader.cpp
g++ -o buildscons\mingw\src\lib_json\json_value.o -c -DWIN32 -DNDEBUG -D_MT -Iinclude src\lib_json\json_value.cpp
g++ -o buildscons\mingw\src\lib_json\json_writer.o -c -DWIN32 -DNDEBUG -D_MT -Iinclude src\lib_json\json_writer.cpp
ar rc buildscons\mingw\src\lib_json\libjson_mingw_libmt.a buildscons\mingw\src\lib_json\json_reader.o buildscons\mingw\src\lib_json\json_value.o buildscons\mingw\src\lib_json\json_writer.o
ranlib buildscons\mingw\src\lib_json\libjson_mingw_libmt.a
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7
  • Please clarify your question. It may help to show the actual error output. Commented May 3, 2012 at 5:54
  • Do you have the compiler output? What are the compiler and linker command lines? Commented May 3, 2012 at 11:15
  • 3
    Are you linking with gcc or g++? Note that your fix will cause null dereference and a nasty crash at runtime when an exception is thrown. Commented May 3, 2012 at 11:19
  • @jpalecek I've added the command line output, I hope it helps - some arguments ( hge, sfml ) are useless but that's because I've put them in my general configuration to avoid linking them in each project I do. Commented May 3, 2012 at 12:28
  • 1
    See my answer to this related question. This sort of issue is usually due to a library/ABI mismatch between your compiler and the compiler that was used to compile the library. Commented May 3, 2012 at 12:36

4 Answers 4

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46

For those coming to this from google (like i did), the real cause of the undefined references to _Unwind_Resume and __gxx_personality_v0 is "using a gcc that uses a different stack unwinding method than dwarf2" [1]

In my case it was attempting to link code compiled with GCC 4.9 upwards with a library compiled with GCC 4.8 or below. The solution is to recompile the library with the same compiler you're building with.

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1 Comment

Good answer. I ran into the __Unwind_Resume error when I was trying to revert to gcc 3 after using gcc 4. I had to go back and recompile two libraries with gcc 3 before I could link them.
1

I encountered that same problem attempting to use g++ -g -std=c++17 ... . I removed that option and, once I had removed use of a C++17 feature, it compiled, linked and ran.

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I finally fixed this by importing into Code::Blocks the source code of JsonCpp and creating the library myself. I am still baffled though as to why the library created with Scons didn't work, since it was using the same compiler that Code::Blocks uses, but at the same time it was not ( or the error wouldn't have been there ).

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The question was already answered for Windows. But on Linux you can also get into this if you mix compiler runtimes (libgcc vs. compiler-rt).

If Clang is using libc++ with compiler-rt by default, compiling with just -stdlib=libstdc++ will produce the above mentioned error (undefined reference to symbol '_Unwind_Resume@@GCC_3.0').

To target libstdc++ from Clang properly, either compile with --rtlib=libgcc -stdlib=libstdc++ or link with the LLVM unwind library using -lunwind. For more detail see LLVM docs - Toolchain.

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