If $CC has --sysroot=/, it is a valid configuration however libtool will then set lt_sysroot to "/".
This means references like $lt_sysroot$libdir become //usr/lib instead of the more normally expected /usr/lib. This may or may not break something but certainly is confusing to the user and gives confusing output. Making "/" simply unset lt_sysroot is much cleaner. * m4/libtool.m4: Improve '/' sysroot handling --- m4/libtool.m4 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/m4/libtool.m4 b/m4/libtool.m4 index 695ccac4..1c8ea182 100644 --- a/m4/libtool.m4 +++ b/m4/libtool.m4 @@ -1256,6 +1256,10 @@ case $with_sysroot in #( yes) if test yes = "$GCC"; then lt_sysroot=`$CC --print-sysroot 2>/dev/null` + # Treat "/" the same a an unset sysroot to avoid ugly // expansion for $lt_sysroot$libdir + if test "$lt_sysroot" = /; then + lt_sysroot= + fi fi ;; #( /*) -- 2.39.2