the default src_compile() returns 1 if it fails: src_compile() { if [ -x ./configure ] ; then econf || return 1 emake || return 1 fi return } but dyn_compile() is not checking the return value. this means that ebuilds cannot safely use the default src_compile() function.
these should be changed to || die. Will do soon.
fix in Portage 2.0.24. Thanks for your patience.