 <p>Turns out this is was a symptom of not handling exceptions. </p> <p>See the <a href="http://stackoverflow.com/questions/23219614/why-gcc-4-1-gcov-reports-100-branch-coverage-and-newer-4-4-4-6-4-8-report/23344292#23344292">related post</a> for a quick fix my turning on -fno-exceptions when compiling.</p>