make_n_bug_report

$ ####################################################
$ # start by building everything
$ make
touch foo.in
echo "foo1.out foo2.out" >> list.ref
mv list.ref list
echo "list contains: `cat list`"
list contains: foo1.out foo2.out
touch `cat list`
date > tgt
rm list
$ # check that build is clean
$ make
make: Nothing to be done for `all'.
$ # yes build is clean
$ # what files were created?
$ ls
foo1.out  foo2.out  foo.in  Makefile  tgt
$ # let's update foo.in
$ touch foo.in
$ # what does make say it will do?
$ make -n
echo "foo1.out foo2.out" >> list.ref
mv list.ref list
echo "list contains: `cat list`"
touch `cat list`
date > tgt
rm list
$ # okay, let's run make
$ make
echo "foo1.out foo2.out" >> list.ref
$ # why didn't make do what "make -n" said it would do? try again?
$ make
echo "foo1.out foo2.out" >> list.ref
$ # nope. what does make say it will do?
$ make -n
echo "foo1.out foo2.out" >> list.ref
mv list.ref list
echo "list contains: `cat list`"
touch `cat list`
date > tgt
rm list
$ ####################################################
$
$
$
$ ####################################################
$ # let's clean up the list files
$ make clean_lists
rm -f list list.ref
$ # what does make say it will do? (now with debugging output)
$ make -r -d -n
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for x86_64-pc-linux-gnu
Reading makefiles...
Reading makefile `Makefile'...
Updating makefiles....
 Considering target file `Makefile'.
  Looking for an implicit rule for `Makefile'.
  No implicit rule found for `Makefile'.
  Finished prerequisites of target file `Makefile'.
 No need to remake target `Makefile'.
Updating goal targets....
Considering target file `all'.
 File `all' does not exist.
  Considering target file `tgt'.
     Considering target file `foo1.out'.
      Looking for an implicit rule for `foo1.out'.
      Trying pattern rule with stem `.'.
      Trying implicit prerequisite `foo.in'.
      Found an implicit rule for `foo1.out'.
       Considering target file `foo.in'.
        Finished prerequisites of target file `foo.in'.
       No need to remake target `foo.in'.
      Finished prerequisites of target file `foo1.out'.
      Prerequisite `foo.in' is newer than target `foo1.out'.
     Must remake target `foo1.out'.
echo "foo1.out foo2.out" >> list.ref
     Successfully remade target file `foo1.out'.
     Considering target file `foo2.out'.
     File `foo2.out' was considered already.
   Considering target file `list'.
    File `list' does not exist.
     Pruning file `foo1.out'.
     Pruning file `foo2.out'.
    Finished prerequisites of target file `list'.
   Must remake target `list'.
mv list.ref list
echo "list contains: `cat list`"
   Successfully remade target file `list'.
   Finished prerequisites of target file `tgt'.
   Prerequisite `list' is newer than target `tgt'.
  Must remake target `tgt'.
touch `cat list`
date > tgt
  Successfully remade target file `tgt'.
 Finished prerequisites of target file `all'.
Must remake target `all'.
Successfully remade target file `all'.
Removing intermediate files...
rm list
$ # see the line that says "Must remake target `list'."
$ # okay, let's run make with debugging output
$ make -r -d
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for x86_64-pc-linux-gnu
Reading makefiles...
Reading makefile `Makefile'...
Updating makefiles....
 Considering target file `Makefile'.
  Looking for an implicit rule for `Makefile'.
  No implicit rule found for `Makefile'.
  Finished prerequisites of target file `Makefile'.
 No need to remake target `Makefile'.
Updating goal targets....
Considering target file `all'.
 File `all' does not exist.
  Considering target file `tgt'.
     Considering target file `foo1.out'.
      Looking for an implicit rule for `foo1.out'.
      Trying pattern rule with stem `.'.
      Trying implicit prerequisite `foo.in'.
      Found an implicit rule for `foo1.out'.
       Considering target file `foo.in'.
        Finished prerequisites of target file `foo.in'.
       No need to remake target `foo.in'.
      Finished prerequisites of target file `foo1.out'.
      Prerequisite `foo.in' is newer than target `foo1.out'.
     Must remake target `foo1.out'.
echo "foo1.out foo2.out" >> list.ref
Putting child 0x0131ce60 (foo1.out) PID 25280 on the chain.
Live child 0x0131ce60 (foo1.out) PID 25280
Reaping winning child 0x0131ce60 PID 25280
Removing child 0x0131ce60 PID 25280 from chain.
     Successfully remade target file `foo1.out'.
     Considering target file `foo2.out'.
     File `foo2.out' was considered already.
   Finished prerequisites of target file `tgt'.
   Prerequisite `list' of target `tgt' does not exist.
  No need to remake target `tgt'.
 Finished prerequisites of target file `all'.
Must remake target `all'.
Successfully remade target file `all'.
$ # see that there is no line mentioning remaking target `list'
$ # again make differs between dry and actual runs
$ ####################################################
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$
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$
$ ####################################################
$ # let's clean up the list files
$ make clean_lists
rm -f list list.ref
$ # let's store the commands make says it would run during the dry run
$ make -n > scratch.sh
$ # let's run those commands
$ sh scratch.sh
list contains: foo1.out foo2.out
$ # now what does make say?
$ make
make: Nothing to be done for `all'.
$ # see that build would be clean if make did what it said it would do during dry-run
$ ####################################################