Why does TinyXML2 give an error when trying to build?

Question

CMake

I am using TinyXML2 to parse game maps from xml. (also using SFML)
Here is the error:

FAILED: project_flag 
: && /Library/Developer/CommandLineTools/usr/bin/c++ -std=c++11 -g -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX12.1.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names  CMakeFiles/project_flag.dir/main.cpp.o CMakeFiles/project_flag.dir/lib/TinyXML2/include/tinyxml2.cpp.o -o project_flag  -Wl,-rpath,/usr/local/lib  /usr/local/lib/libsfml-graphics.2.5.1.dylib  /usr/local/lib/libsfml-audio.2.5.1.dylib  /usr/local/lib/libsfml-network.2.5.1.dylib  /usr/local/lib/libsfml-window.2.5.1.dylib  /usr/local/lib/libsfml-system.2.5.1.dylib && :
Undefined symbols for architecture x86_64:
  "TiXmlString::nullrep_", referenced from:
      TiXmlString::quit() in main.cpp.o
  "TiXmlDocument::LoadFile(TiXmlEncoding)", referenced from:
      Level::LoadFromFile(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main.cpp.o
      AnimationManager::loadFromXML(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, sf::Texture&) in main.cpp.o
  "TiXmlDocument::TiXmlDocument(char const*)", referenced from:
      Level::LoadFromFile(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main.cpp.o
      AnimationManager::loadFromXML(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, sf::Texture&) in main.cpp.o
  "TiXmlNode::~TiXmlNode()", referenced from:
      TiXmlDocument::~TiXmlDocument() in main.cpp.o
  "TiXmlElement::Attribute(char const*) const", referenced from:
      Level::LoadFromFile(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main.cpp.o
      AnimationManager::loadFromXML(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, sf::Texture&) in main.cpp.o
  "TiXmlNode::FirstChildElement(char const*) const", referenced from:
      TiXmlNode::FirstChildElement(char const*) in main.cpp.o
  "TiXmlNode::NextSiblingElement(char const*) const", referenced from:
      TiXmlNode::NextSiblingElement(char const*) in main.cpp.o
  "vtable for TiXmlDocument", referenced from:
      TiXmlDocument::~TiXmlDocument() in main.cpp.o
  NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

Why could this error appear and how to solve it?

Answer 1

The error is that the library with definitions TiXmlDocument::LoadFileof other symbols is not passed to the linker during assembly. It is necessary in CMake, for example, to add link_libraries or target_link_libraries indicating TinyXML2, just like you did with SFML.