[bug #29620] Implicit rule search is still sensitive to random side effects

[Matt McCutchen]

URL:
  <http://savannah.gnu.org/bugs/?29620>

                 Summary: Implicit rule search is still sensitive to random
side effects
                 Project: make
            Submitted by: hashproduct
            Submitted on: Tue 20 Apr 2010 04:14:59 PM EDT
                Severity: 3 - Normal
              Item Group: Bug
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: CVS
        Operating System: POSIX-Based
           Fixed Release: None
           Triage Status: None

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Details:

The implicit rule search algorithm from the manual, step 5c:

"Test whether all the prerequisites exist or ought to exist.
(If a file name is mentioned in the makefile as a target or
as an explicit prerequisite, then we say it ought to exist.)"

But this is not what the implementation of "ought to exist" does.  It checks
whether the prerequisite has been entered as a file.

The requirement that the prerequisite be marked as a target was removed in
bug #17752 in the name of making implicit rule search less sensitive to random
side effects from other things going on in the makefile.  However, I'd argue
that the change has hardly made any progress toward that goal, since the
search is still sensitive to whether other activity in the makefile has
entered the prerequisites as files.  Consider this example:

test.foo:

enter-file-%: % ; $(info entering file $<)

%.foo : baz ; $(info chose $< to make $@)
%.foo : bar ; $(info chose $< to make $@)

ba% : ;

The output with the latest CVS make:

$ make -f still-order-dependent.mk test.foo enter-file-bar
chose baz to make test.foo
make: `test.foo' is up to date.
entering file bar
make: `enter-file-bar' is up to date.

$ make -f still-order-dependent.mk enter-file-bar test.foo
entering file bar
make: `enter-file-bar' is up to date.
chose bar to make test.foo
make: `test.foo' is up to date.

Maybe it would be good to implement what the manual says: flag files that
were explicitly mentioned in the makefile and have the implicit rule search
check for that flag.




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