[gnugo-devel] Unmotivated rebuilding

[Gunnar Farneback]

As I guess many people have noticed and become irritated by, when you
make a second build many files are needlessly recompiled. More
exactly, if you do this:

download tarball, unpack, configure
make
make

the second make will, regardless whether you have changed anything,
rebuild a few files, including the somewhat time consuming joseki
database.

The problem is with the file sgf_properties.h, which is provided in
the distribution but also built by the program sgfgen from the
specification file sgf_properties.def. Furthermore, sgf_properties.h
is built *after* the source files for libsgf.a have been compiled.
Since the latter files depend on sgf_properties.h, the second make
will notice that sgf_properties.h is newer and rebuild them.

I can see four potential solutions:

1. Make sure sgf_properties.h is newer than sgfgen.c and
sgf_properties.def so that it normally doesn't have to be rebuilt.

2. Modify the makefile so that sgf_properties.h is built before the
libsgf.a source files are compiled.

3. Remove sgf_properties.h from the distribution and let it be
generated in the build.

4. Stop sgf_properties.h from being built at all by default. We'd want
to keep the make target so that people can rebuild the file if they
modify sgf_properties.def. This is quite unlikely though, so it's fine
if they have to run the make taret by hand.

I doubt 1 is practically feasible. 2 is a good solution if automake
makes it possible. I have no idea how to do it or whether it can be
done. 3 should be simple to implement, but maybe there's some
complication there which I fail to notice. 4 is possibly the best
solution and Dan thinks it can be done.

Can someone remind me why we are shipping a prebuilt sgf_properties.h
to begin with?

In the mean time, this patch makes a minor cleanup of sgf/Makefile.am.

/Gunnar

Index: sgf/Makefile.am
===================================================================
RCS file: /cvsroot/gnugo/gnugo/sgf/Makefile.am,v
retrieving revision 1.4
diff -u -r1.4 Makefile.am
--- sgf/Makefile.am     6 Nov 2001 16:36:51 -0000       1.4
+++ sgf/Makefile.am     28 Mar 2002 22:45:53 -0000
@@ -2,7 +2,7 @@
 
 sgfgen_SOURCES = sgfgen.c
 
-EXTRA_DIST = sgf_extras.def sgf_properties.def sgfgen.dsp sgf.dsp sgfgen.dsp
+EXTRA_DIST = sgf_extras.def sgf_properties.def sgfgen.dsp sgf.dsp
 
 noinst_HEADERS = \
        sgftree.h\
@@ -15,9 +15,7 @@
 DISTCLEANFILES = *~
 
 INCLUDES =\
-       -I$(top_srcdir)/engine\
        -I$(top_srcdir)/utils\
-       -I$(top_srcdir)/interface
 
 noinst_LIBRARIES = libsgf.a