On Mon, 2006-06-26 at 04:34 +0000, Harlan Stenn wrote: > We are told that we should not use CPPFLAGS or CFLAGS in a Makefile.am, > as they are for users. That's only partially true.
More precisely: You should not override user-supplied CPPFLAGS, CFLAGS, CXXFLAGS, LIBS etc. Appending something to these vars would be OK, provided the user-provided settings "always win". > The trick is that if we use a configure.ac file to help decide what > flags may be needed, >inside< this configure script we need to use > CFLAGS and CPPFLAGS to effect the running of configure. Depends on what you add to *FLAGS. One standard approach would be to use *FLAGS as package-global FLAGS and AM_*FLAGS as per-Makefile.am FLAGS, i.e. not to AC_SUBST(AM_*FLAGS) inside of a configure.ac, but set up AM_*FLAGS inside of each Makefile.am anew from other AC_SUBST'ed vars to provide more fine-grained control over FLAGS. How to handle this inside of a configure.ac is up to you and depends on your package's demands. The big pitfall inside of all this trying to setup optimization flags. In general, these should not be under a configure.ac's control, but under user control. My recommendation is not trying to setup optimization flags. Ralf
