ACLOCAL_AMFLAGS was deprecated in 2012 according to https://lists.gnu.org/archive/html/automake-patches/2012-12/msg00079.html
Yet, the gnulib git repository contains a couple of references to it (as of commit 2f8b355aeacb448d13bab9cb3cdaaeea649a4664): $ grep -r ACLOCAL_AMFLAGS gnulib-tool: echo "ACLOCAL_AMFLAGS = -I ${testsbase_inverse}/${m4base}" gnulib-tool: func_note_Makefile_am_edit "" ACLOCAL_AMFLAGS "-I ${m4base}" gnulib-tool: echo "ACLOCAL_AMFLAGS = -I $m4base" gnulib-tool: aclocal_amflags=`sed -n -e 's/^ACLOCAL_AMFLAGS[ ]*=\(.*\)$/\1/p' "$destdir"/Makefile.am` doc/gnulib-tool.texi: - mention "-I m4" in ACLOCAL_AMFLAGS in Makefile.am, doc/gnulib-tool.texi:@file{gnulib-comp.m4}. Use the @code{ACLOCAL_AMFLAGS} specifier in doc/gnulib-tool.texi:ACLOCAL_AMFLAGS = -I m4 ChangeLog: ACLOCAL_AMFLAGS parsing state machine. I originally intended to just send a patch to update the documentation, but now I’m not certain if that in itself is a good idea without also updating the code, and I don’t have the time to wrestle with large shell scripts currently :). -- Best regards, Michael