Gentoo's binutils does not install demangle.h. There are cases when it's needed. Debian has it in binutils-dev. Why should gentoo not have it? Reproducible: Always
Woo, demangle.h seems popular: https://bugs.mageia.org/show_bug.cgi?id=4661
Please post your `emerge --info sys-devel/binutils' output in a comment.
Created attachment 327232 [details] emerge --info binutils A bit over 16KiB so added as an attachment
(In reply to comment #0) we install what upstream installs. upstream doesn't install demangle.h thus we don't install it.
(In reply to comment #4) well, that's not entirely true, but it doesn't matter http://sources.gentoo.org/eclass/toolchain-binutils.eclass?r1=1.119&r2=1.120