GNU make troubleshooting

[Bruno Haible]

Hi all,

In recent build system discussions on gnu-prog-discuss, the suggestion was
made [1] to use GNU make's power instead of autoconf, automake, and POSIX make.

I think GNU make is lacking transparency / debuggability / serviceability
features before this suggestion makes sense. Especially for newbie users
and complex makefiles.

I know about, and have occasionally used, the GNU make options
  -n, --dry-run
  -d
  -p
  -t, --touch
and they don't fulfil my needs.

In particular, four aspects of transparency / debuggability / serviceability
are lacking in GNU make.

1) Print the total of the Makefile and all included Makefiles.
   Like what "gcc -E" does with C code.
   I don't need this when using Automake, because Automake resolves the
   'include' statements before generating a Makefile. But if people advocate
   to use GNU make without Automake, it becomes a requirement. As a developer,
   I don't want to check each 'include' statement, recursively, manually.
   A tool should do that.

   This would also answer a question on #gnu today:
   "Is there a way to figure out where the rule is coming from? The main
    issue is "target file 'clean' has both : and :: entries. Stop." But
    I'm unable to figure out where the last clean: target is coming from."

   Probably this facility should have an option to show the macroexpanded /
   not macroexpanded Makefile sources.

2) Where is the Makefile source for each command that gets executed?
   For each command that gets executed, print not only the command (or
   nothing if the line begins with '@'), but also the location (which
   Makefile, which line number).

   This would help in a number of situations.

   I tried -d a couple of times, and it produced a ton of output, that
   was too much for me to make sense of. Probably 10% to 20% of the
   developers in general have trace filtering skills, that is, know how
   to extract the essential information from a heap of output. It's not
   part of my skills.

3) Single-stepping or tracing function execution. One project (GNU libc)
   makes profound use of GNU make functions, and it was always painful
   for me to understand what results to expect from a complex use of
   $(foo ...). Even from the simple text-manipulating functions [2].

   There is an option --eval=STRING, but I don't think it fulfils the
   need.

4) A documentation chapter regarding troubleshooting, that explains
   how to understand what 'make' is doing in a particular case.
   Chapters 2-8 and 10-12 explain how to set up the input to 'make'.
   Chapters 9 and 13 explain operational aspects, but none goes into
   troubleshooting details.
   For a complex program like GNU make, probably at least 10 or 20 pages
   on this topic are needed.

Best regards,

                Bruno

[1] https://www.airs.com/blog/archives/95
[2] https://www.gnu.org/software/make/manual/html_node/Functions.html