title: Including C++ headers, "..." vs. <...> style, official ISO/IEC opinion?
body: <p>I know, this is an old question that has been asked many times <a href="https://stackoverflow.com/questions/21593/what-is-the-difference-between-include-filename-and-include-filename">before</a>. I agree with the common answer that <code>#include &lt;filename&gt;</code> should be used for system headers and <code>#include "filename"</code> should be used for project-local headers.</p>
  
  <p>However, now I found <a href="http://open-std.org/JTC1/SC22/WG21/docs/papers/2018/p1204r0.html" rel="nofollow noreferrer">this paper</a> from the ISO/IEC C++ Tools Working Group, which states the following:</p>
  
  <blockquote>
    <p>All headers within a project should be included using the <code>&lt;&gt;</code> style inclusion and contain the project name as a directory prefix. And all headers means all headers public, private, or implementation detail, in executables or in libraries.</p>
  </blockquote>
  
  <p>They also give an explanation:</p>
  
  <blockquote>
    <p>The problem with the <code>""</code> style inclusion is if the header is not found relative to the including file, most implementations will continue looking for it in the include search paths, the same as for <code>&lt;&gt;</code>. As a result, if the header is not present in the right place (for example, because it was mistakenly not listed as to be installed), chances are that a completely unrelated header with the same name will be found and included. Needless to say, debugging situations like these is unpleasant.</p>
  </blockquote>
  
  <p>I don't understand this. Why does this problem not occur with the <code>&lt;&gt;</code> style?</p>
  
  <p>Bonus question: What's the status of such a paper anyway? Can it be considered an official recommendation of the ISO/IEC C++ consortium, peer-reviewed and acknowledged by many experts? Or is it just a proposal by someone in order to trigger a discussion?</p>