id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
121	Sysroot build of gcc needs --includedir to avoid libstdc++/glibc compatibility issues	kev	clfs-commits@…	"http://cross-lfs.org/view/clfs-sysroot/x86/final-system/gcc.html

The configure needs the follwing added:
--includedir=${CLFS}/include

Without this gcc is built using /include, i.e. the include files on the build system.
This works if you're build system includes are identical to CLFS includes.
It does not work if there are differences. 
Symptoms = mismatch between libstdc++ and glibc such that funny link errors appear,
e.g. on a g++ compile&link you might see:

gnu/lib/../lib64/libstdc++.so: undefined reference to `std::basic_filebuf<char, std::char_traits<char> >::seekoff(long, std::_Ios_Seekdir, std::_Ios_Openmode)
"	task	closed	major	CLFS Sysroot 1.0.0	BOOK	CLFS Sysroot 1.0.0	invalid	gcc includedir seekoff