Building libvirt with CFLAGS=-g doesn't work as expected: gcc runs without -g. That was due to the following assignment that gives CFLAGS the value of an undefined variable. 2007-03-23 Jim Meyering <jim(a)meyering.net&gt; * acinclude.m4: Remove bogus CFLAGS=$undefined_var assignment that would clobber any CFLAGS setting from e.g., ./autogen.sh CFLAGS=-g. Reported by David Lutterkort. Index: acinclude.m4 =================================================================== RCS file: /data/cvs/libvirt/acinclude.m4,v retrieving revision 1.3 diff -u -p -r1.3 acinclude.m4 --- acinclude.m4 21 Mar 2007 15:22:31 -0000 1.3 +++ acinclude.m4 23 Mar 2007 18:52:55 -0000 @@ -59,8 +59,6 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ unset option unset try_compiler_flags - CFLAGS="$realsave_CFLAGS" - AC_ARG_ENABLE(iso-c, AC_HELP_STRING([--enable-iso-c], [Try to warn if code is not ISO C ]),,