Same procedure as every year: Only programs that don&#x27;t conform to the C&#x2F;C++ standard.<p>Not counting true compiler bugs of course.<p>Edit: The release notes at <a href="https:&#x2F;&#x2F;gcc.gnu.org&#x2F;gcc-6&#x2F;changes.html" rel="nofollow">https:&#x2F;&#x2F;gcc.gnu.org&#x2F;gcc-6&#x2F;changes.html</a> mention three programs that apparently will break:<p><i>Value range propagation now assumes that the this pointer of C++ member functions is non-null. This eliminates common null pointer checks but also breaks some non-conforming code-bases (such as Qt-5, Chromium, KDevelop)</i>