[Bug libstdc++/69881] with gcc-6 of today building gcc-4.9 fails

[bernd.edlinger at hotmail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69881

--- Comment #1 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
note: back-porting r233572 will still be necessary to build 4.9 with gcc-6
but the build fails earlier than that.