Re: Avoid certain spurious `testsuite' rebuilds

[Noah Misch]

Hi Ralf, autoconf-patches,

On Sun, Apr 02, 2006 at 06:36:58PM +0200, Ralf Wildenhues wrote:
> > > * Noah Misch wrote on Fri, Mar 31, 2006 at 06:09:06PM CEST:
> > > > +       test -f updated && mv -f updated $@; :
> 
> Shouldn't that be
>       test -f updated && mv -f updated $@ || :
> 
> to cope with make implementations invoking `sh -e -c'?

The `:' was not necessary at all; I don't know why I left it there.

> Thanks.  I guess it's ok to install.  It still doesn't work with OpenBSD
> make though; I think it's because it does not check again that the
> stamp-tgat time is not updated after its rule is executed:

This could be same problem affecting FreeBSD make.


Removing tests/ac*.at from CVS had the virtue of revealing a bug in previous
iterations of this patch: when foo.at should be empty and there was no existing
foo.at, mktests.sh as patched would not create one.

Automake has a similar challenge: avoid rebuilding everything when `config.h.in'
or `config.status' changes, but the resulting `config.h' remains unchanged.  Its
implementation is somewhat cleaner than mine, so I spent some time trying to
adapt it.  I could not find a way to do so without precluding parallel make or
using one stamp file per lib/autoconf/*.m4.  Even then, the optimization failed
on FreeBSD (as it does for Automake).


I substantially rewrote the patch.  It's much simpler now, and the optimization
works with GNU, FreeBSD, NetBSD, Tru64, and HP-UX Make programs.  It's broken
with respect to parallel make, but that's nothing new.

We now trigger the TESTSUITE_GENERATED_AT update from check-local, so `make -C
tests ./testsuite' may build a testsuite using out-of-date tests/ac*.at.  I
couldn't find a way around this without introducing more serious flaws.

What do you think?


2006-04-05  Noah Misch  <address@hidden>

        Do not rebuild `testsuite' when a lib/autoconf/*.m4 edit does not affect
        the generated test cases.

        * tests/Makefile.am (stamp_tgat): New macro.  Distribute.
        (check_local): Depend on $(stamp_tgat).
        (check_tgat): New macro, from old TESTSUITE_GENERATED_AT commands.
        (stamp_tgat): New rule.
        (TESTSUITE_GENERATED_AT): Remove prerequisites.
        * tests/mktests: Only touch the products if they would change.
        * tests/.cvsignore: Update.

diff -urp -X dontdiff ac-clean/tests/.cvsignore 
ac-simplerer_ifchanged/tests/.cvsignore
--- ac-clean/tests/.cvsignore   2006-04-02 14:59:44.000000000 -0400
+++ ac-simplerer_ifchanged/tests/.cvsignore     2006-04-05 12:22:36.000000000 
-0400
@@ -26,6 +26,7 @@ autoupdate
 expr
 ifnames
 package.m4
+stamp-tgat
 testsuite
 testsuite.dir
 wrapper.in
diff -urp -X dontdiff ac-clean/tests/Makefile.am 
ac-simplerer_ifchanged/tests/Makefile.am
--- ac-clean/tests/Makefile.am  2006-03-06 16:13:22.000000000 -0500
+++ ac-simplerer_ifchanged/tests/Makefile.am    2006-04-05 15:51:40.000000000 
-0400
@@ -1,7 +1,7 @@
 ## Process this file with automake to create Makefile.in. -*-Makefile-*-
 
 ## Makefile for Autoconf testsuite.
-## Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
+## Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006
 ## Free Software Foundation, Inc.
 
 ## This program is free software; you can redistribute it and/or modify
@@ -79,6 +79,10 @@ $(wrappers): wrapper.in
 ## Test suite.  ##
 ## ------------ ##
 
+# Timestamp for TESTSUITE_GENERATED_AT.
+stamp_tgat = $(srcdir)/stamp-tgat
+EXTRA_DIST += $(stamp_tgat)
+
 TESTSUITE_GENERATED_AT = \
        $(srcdir)/aclang.at \
        $(srcdir)/acc.at \
@@ -126,7 +130,7 @@ clean-local:
        rm -f *.tmp
        rm -f -r autom4te.cache
 
-check-local: atconfig atlocal $(TESTSUITE)
+check-local: atconfig atlocal $(stamp_tgat) $(TESTSUITE)
        $(SHELL) $(TESTSUITE) $(TESTSUITEFLAGS)
 
 # Run the test suite on the *installed* tree.
@@ -161,9 +165,17 @@ AUTOCONF_FILES = $(autoconfdir)/general.
                 $(autoconfdir)/types.m4 \
                 $(autoconfdir)/programs.m4
 
-$(TESTSUITE_GENERATED_AT): mktests.sh $(AUTOCONF_FILES)
-       cd $(srcdir) && ./mktests.sh \
-         `echo " "$(AUTOCONF_FILES) | sed 's, [^ ]*/, ../lib/autoconf/,g'`
+check_tgat = cd $(srcdir) && ./mktests.sh \
+            `echo " "$(AUTOCONF_FILES) | sed 's, [^ ]*/, ../lib/autoconf/,g'`
+
+## Check and possibly update TESTSUITE_GENERATED_AT when AUTOCONF_FILES change.
+$(stamp_tgat): mktests.sh $(AUTOCONF_FILES)
+       $(check_tgat)
+       echo 'Timestamp for validation of tests/ac*at.' >$@
+
+## Rebuild missing TESTSUITE_GENERATED_AT.
+$(TESTSUITE_GENERATED_AT):
+       $(check_tgat)
 
 
 ## maintainer-check ##
diff -urp -X dontdiff ac-clean/tests/mktests.sh 
ac-simplerer_ifchanged/tests/mktests.sh
--- ac-clean/tests/mktests.sh   2006-04-04 15:42:35.000000000 -0400
+++ ac-simplerer_ifchanged/tests/mktests.sh     2006-04-05 15:17:04.000000000 
-0400
@@ -262,12 +262,20 @@ MK_EOF
   # preserves the old version of the file.  If there is nothing to
   # check, output /rien du tout/[1].
   if grep AT_CHECK ac$base.tat >/dev/null 2>&1; then
-    mv -f ac$base.tat ac$base.at
-    # Help people not to update these files by hand.
-    chmod a-w ac$base.at
+    if diff ac$base.at ac$base.tat >/dev/null 2>&1; then
+       rm -f ac$base.tat
+    else
+       diff ac$base.at ac$base.tat || :
+       mv -f ac$base.tat ac$base.at
+       # Help people not to update these files by hand.
+       chmod a-w ac$base.at
+    fi
   else
-    rm -f ac$base.tat ac$base.at
-    touch ac$base.at
+    rm -f ac$base.tat
+    if test \! -f ac$base.at || test -s ac$base.at; then
+       rm -f ac$base.at
+       touch ac$base.at
+    fi
   fi
 done