tests/spy.test

   1 #! /bin/sh
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  20
  21 # Check whether double colon rules work.  The Unix V7 make manual
  22 # mentions double-colon rules, but POSIX does not.  They seem to be
  23 # supported by all Make implementation as we can tell. This test case
  24 # is a spy: we want to detect if there exist implementations where
  25 # these do not work.  We might use these rules to simplify the rebuild
  26 # rules (instead of the $? hack).
  27
  28 # Tom Tromey write:
  29 # | In the distant past we used :: rules extensively.
  30 # | Fran?ois convinced me to get rid of them:
  31 # |
  32 # | Thu Nov 23 18:02:38 1995  Tom Tromey  <tromey@cambric>
  33 # | [ ... ]
  34 # |         * subdirs.am: Removed "::" rules
  35 # |         * header.am, libraries.am, mans.am, texinfos.am, footer.am:
  36 # |         Removed "::" rules
  37 # |         * scripts.am, programs.am, libprograms.am: Removed "::" rules
  38 # |
  39 # |
  40 # | I no longer remember the rationale for this.  It may have only been a
  41 # | belief that they were unportable.
  42
  43 # On a related topic, the Autoconf manual has the following text:
  44 # |     `VPATH' and double-colon rules
  45 # |           Any assignment to `VPATH' causes Sun `make' to only execute
  46 # |           the first set of double-colon rules.  (This comment has been
  47 # |           here since 1994 and the context has been lost.  It's probably
  48 # |           about SunOS 4.  If you can reproduce this, please send us a
  49 # |           test case for illustration.)
  50
  51 # We already know that overlapping ::-rule like
  52 #
  53 #   a :: b
  54 #       echo rule1 >> $@
  55 #   a :: c
  56 #       echo rule2 >> $@
  57 #   a :: b c
  58 #       echo rule3 >> $@
  59 #
  60 # do not work equally on all platforms.  It seems that in all cases
  61 # Make attempts to run all matching rules.  However at least GNU Make,
  62 # NetBSD Make, and FreeBSD Make will detect that $@ was updated by the
  63 # first matching rule and skip remaining matches (with the above
  64 # example that means that unless `a' was declared PHONY, only "rule1"
  65 # will be appended to `a' if both b and c have changed).  Other
  66 # implementations like OSF1 Make and HP-UX Make do not perform such a
  67 # check and execute all matching rules whatever they do ("rule1",
  68 # "rule2", abd "rule3" will all be appended to `a' if b and c have
  69 # changed).
  70
  71 # So it seems only non-overlapping ::-rule may be portable.  This is
  72 # what we check now.
  73
  74 . ./defs || exit 1
  75
  76 set -e
  77
  78 cat >Makefile <<\EOF
  79 a :: b
  80         echo rule1 >> $@
  81 a :: c
  82         echo rule2 >> $@
  83 EOF
  84
  85 touch b c
  86 $sleep
  87 : > a
  88 $MAKE
  89 test "`cat a`" = ''
  90 $sleep
  91 touch b
  92 $MAKE
  93 test "`cat a`" = rule1
  94 : > a
  95 $sleep
  96 touch c
  97 $MAKE
  98 test "`cat a`" = rule2