depcomp tests: avoid redundant runs for libtool tests

When running libtool-oriented tests, our 'depcomp.sh' script used
to run the same checks thrice: once after having run configure
with the '--disable-shared' option, once after having run it with
the '--enable-shared' option, and once by allowing configure to
automatically select which kind of library (or libraries) to build.

This was done to offer extra coverage for the less-common depmodes
(like "aix" of "hp2") where the name of the compiler-generated
depfiles can depend on whether libtool is in use *and* on which
kind of libraries libtool is building (static, shared, or both).
About this, see commit 'Release-1-10-24-ge89ec38' of 28-03-2007,
"* lib/depcomp (aix): Rewrite depmode in the spirit of the tru64
one".

But that extra coverage came at the price of *considerably* slowing
down the depcomp libtool-oriented tests, since for each of them the
tested source tree was configured and built *twelve* times (rather
than "just" four as it is for the non-libtool case).

So, to strike a balance between coverage and speed, we now run the
libtool-oriented tests with the three different configuration modes
*only* when it is possible that the depmode that will get selected
is one of those which can actually benefit from the extra coverage.

* tests/depcomp.sh: Adjust to only run the threefold libtool tests
when that can truly be potentially useful.  Add related explanatory
comments.

diff --git a/tests/depcomp.sh b/tests/depcomp.sh
index 67db770..a53c0b5 100755 (executable)
--- a/tests/depcomp.sh
+++ b/tests/depcomp.sh
@@ -148,7 +148,6 @@ mkdir build-aux sub src src/sub2
 
 case $depcomp_with_libtool in
   yes)
-    plan_ 84
     po=Plo objext=lo a=la
     normalized_target=libfoo_la
     LIBPRIMARY=LTLIBRARIES LINKADD=LIBADD
@@ -166,7 +165,6 @@ case $depcomp_with_libtool in
     }
     ;;
   no)
-    plan_ 28
     po=Po objext='$(OBJEXT)' a=a
     normalized_target=foo
     LIBPRIMARY=LIBRARIES LINKADD=LDADD
@@ -260,14 +258,42 @@ $ACLOCAL && $AUTOCONF && $AUTOMAKE -a \
 test -f build-aux/depcomp \
   || fatal_ "depcomp script not installed"
 
+# To offer extra coverage for the depmodes (like "aix" of "hp2") where the
+# name of the compiler-generated depfiles can depend on whether libtool is
+# in use *and* on which kind of libraries libtool is building (static,
+# shared, or both), we would like to run the libtool-oriented tests thrice:
+# once after having run configure with the '--disable-shared' option, once
+# after having run it with the '--enable-shared' options, and once by
+# leaving it to configure to automatically select which kind of library (or
+# libraries) to build.
+#
+# But doing such three-fold checks unconditionally for all the depmodes
+# would slow down the already too slow libtool tests unacceptably (up to a
+# 150-200% factor), with no real gain in coverage for most of the depmodes.
+# So, since the depmodes that would benefit from the extra tests are never
+# forced to configure in out tests below, but can only be automatically
+# selected by '--enable-dependency-tracking', we make this threefold check
+# only in this later case.
+
 case $depmode in
   auto)
+    plan_ 84
+    do_all_tests ()
+    {
+      do_test default
+      do_test noshared --disable-shared
+      do_test nostatic --disable-static
+    }
     displayed_depmode='..*' # At least one character long.
     cfg_deptrack=--enable-dependency-tracking ;;
   disabled)
+    plan_ 28
+    do_all_tests() { do_test; }
     displayed_depmode=none
     cfg_deptrack=--disable-dependency-tracking ;;
   *)
+    plan_ 28
+    do_all_tests() { do_test; }
     displayed_depmode="(cached) $depmode"
     cfg_deptrack="$cachevar=$depmode"
     # Sanity check: ensure the cache variable we force is truly
@@ -378,13 +404,7 @@ do_test ()
 }
 
 for vpath in no simple long absolute; do
-  if test $depcomp_with_libtool = no; then
-    do_test
-  else
-    do_test default
-    do_test noshared --disable-shared
-    do_test nostatic --disable-static
-  fi
+  do_all_tests
 done
 
 :