JSONCPP 合并链接错误

Question

I am trying to use the amalgamated version of jsoncpp(the latest version), but it is producing unresolved external symbol link errors. The code I am using is

#include <json/json.h>

int main(){
   Json::Value root;
   return 0;
}

and it is giving me the error

1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall Json::Value::~Value(void)" (??1Value@Json@@QAE@XZ) referenced in function _main
1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall Json::Value::Value(enum Json::ValueType)" (??0Value@Json@@QAE@W4ValueType@1@@Z) referenced in function _main

Answer 1

Probably you didn't include the JSONCPPs *.cpp file into your project (they have to be compiled and linked). If the library gets compiled to a static library, you have to tell the linker what to link.

Answer 2

I got this when trying to link x86 version of JsonCpp in my x64 build. I did not notice that Vcpkg behaves as if VCPKG_DEFAULT_TRIPLET=x86-windows was defined, unless it's told otherwise.

I saw the following entry in the build log when that was happening

C:\\Tools\\vcpkg\\installed\\x86-windows\\debug\\lib\\jsoncpp.lib : warning LNK4272: library machine type 'x86' conflicts with target machine type 'x64' [C:\\projects\\qpid-proton\\BLD\\cpp\\qpid-proton-cpp.vcxproj]