[Bug c++/85145] New: GCC 8 regression: include_next broken icw/ --with-gxx-include-dir

[jeroen at berkeley dot edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85145

            Bug ID: 85145
           Summary: GCC 8 regression: include_next broken icw/
                    --with-gxx-include-dir
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jeroen at berkeley dot edu
  Target Milestone: ---

See downstream issue here: https://github.com/niXman/mingw-builds/issues/452

This is GCC 8.0.1 20180330. g++ gives errors like:

C:/gcc8/mingw32/i686-w64-mingw32/include/c++/cstdlib:75:15: fatal error:
stdlib.h: No such file or directory
 #include_next <stdlib.h>

And 

C:/gcc8/mingw32/i686-w64-mingw32/include/c++/cmath:45:15: fatal error: math.h:
No such file or directory
 #include_next <math.h>

The problem went away when I did a rebuild of mingw-w64 without
--with-gxx-include-dir.