Hi, Paul and Jim approved the idea to give a recommendation about how to set up the -I options in AM_CPPFLAGS for dealing with VPATH builds.
Originally I wanted to document this in the Autoconf manual, but I didn't find the appropriate place: The Autoconf manual talks more about the CPPFLAGS variable as an environment variable, and is silent about how the user is meant to write his Makefile.in files. So here's a proposal for the Automake manual. [1] http://lists.gnu.org/archive/html/bug-gnulib/2011-07/msg00443.html [2] http://lists.gnu.org/archive/html/bug-gnulib/2011-07/msg00448.html 2011-07-30 Bruno Haible <br...@clisp.org> Document how to compose the -I options in AM_CPPFLAGS. * doc/automake.texi (Program Variables): Recommend -I options to both the build directory and the source directory when needed. --- doc/automake.texi.orig Sun Jul 31 02:35:24 2011 +++ doc/automake.texi Sun Jul 31 02:34:29 2011 @@ -6022,6 +6022,16 @@ @code{AM_CONFIG_HEADER}). You can disable the default @option{-I} options using the @option{nostdinc} option. +When a file to be included is generated during the build and not part +of a distribution tarball, its location is under @code{$(builddir)}, +not under @code{$(srcdir)}. This matters for builds outside the source +tree (@pxref{VPATH Builds}). Therefore we recommend to use a pair of +@option{-I} options: @samp{-Isome/subdir -I$(srcdir)/some/subdir} or +@samp{-I$(top_builddir)/some/subdir -I$(top_srcdir)/some/subdir}. +Here the reference to the build tree should come before the reference +to the source tree, so that accidentally leftover generated files in +the source directory are ignored. + @code{AM_CPPFLAGS} is ignored in preference to a per-executable (or per-library) @code{_CPPFLAGS} variable if it is defined. -- In memoriam Ebrahim Berookhim <http://www.jewishjournal.com/iranianamericanjews/item/conversations_about_berookhims_execution_30_years_ago_in_iran/>
