title: Compiling an Old C++ library
body: <p>I am pretty new to C++ and am using gcc 7.5.0 compiler. I want to use the following  <a href="https://github.com/ryanrossi/pmc" rel="nofollow noreferrer">Parallel Max Clique (PMC)</a> library in my code. So I downloaded the whole and repo and added the folder to my current working directory (where my main.cpp i.e. the program in which I want to include the pmc library, is). After building the file I got the following error :</p>
  <p><strong>&quot;undefined reference to `pmc::pmc_graph::pmc_graph(std::__cxx11::basic_string&lt;char, std::char_traits, std::allocator &gt; const&amp;)'|&quot;</strong></p>
  <p>Now, I know why this is happening, this is happening because the <a href="https://github.com/ryanrossi/pmc" rel="nofollow noreferrer">PMC Library</a> was written in an old compiler, and hence I am probably trying to link together object files that were compiled with different values for the _GLIBCXX_USE_CXX11_ABI macro. <a href="https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html" rel="nofollow noreferrer">check link</a>. The solution is to ensure that my underlying libraries (i.e. <a href="https://github.com/ryanrossi/pmc" rel="nofollow noreferrer">PMC library</a>) and my current cpp code(i.e. main.cpp) are compiled with either ABI off. Google search says that I have to build the whole code with   <strong>-D_GLIBCXX_USE_CXX11_ABI=0</strong>. How shall I do it?? I am very confused. Is there any tutorial as to how shall I do it. I am currently using VScode/CodeBlocks.</p>
  <p>Thanks a lot in Advance.</p>