Includes of system headers are never implicitly relative to the source file by bavison · Pull Request #282 · cppcheck-opensource/simplecpp

…e file

Sometimes, #include directives with angle-bracket filespec delimiters are
used (or abused) to defeat the preprocessor's behaviour where it tries to
find a header file at a path relative to the file containing the directive.

Without this fix, any non-root header file, foo/bar.h, which does
  #include <bar.h>
while intending to include a root-level header file, will instead enter an
infinite inclusion loop, terminating when the inclusion stack overflows
with a "#include nested too deeply" error.