Thanks for the fast reply, I installed unifdef, and then ran the command you gave me. Then I ran the configure again, but it looks like something is even worse now: checking for a BSD-compatible install... /usr/bin/ginstall -c checking whether build environment is sane... yes checking for gawk... gawk checking whether make sets $(MAKE)... yes checking whether to enable maintainer-specific portions of Makefiles... no checking for style of include used by make... GNU checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ANSI C... none needed checking dependency style of gcc... gcc3 checking for library containing strerror... none required checking for gcc... (cached) gcc checking whether we are using the GNU C compiler... (cached) yes checking whether gcc accepts -g... (cached) yes checking for gcc option to accept ANSI C... (cached) none needed checking dependency style of gcc... (cached) gcc3 checking for gcc... (cached) gcc checking whether we are using the GNU C compiler... (cached) yes checking whether gcc accepts -g... (cached) yes checking for gcc option to accept ANSI C... (cached) none needed checking dependency style of gcc... (cached) gcc3 checking how to run the C preprocessor... /lib/cpp configure: error: C preprocessor "/lib/cpp" fails sanity check This never happened in the previous attempts to configure the source. Thanks again, Eugéne