Re: Wording in GNU Make manual regarding phony targets

[Paul D. Smith]

%% "R. Bernstein" <address@hidden> writes:

  rb> Recently Bruno Haible point this out from the GNU Make manual:

  rb>   A phony target should not be a prerequisite of a real target file;
  rb>   if it is, its commands are run every time make goes to update
  rb>   that file.  As long as a phony target is never a prerequisite of a
  rb>   real target, the phony target commands will be executed only when the
  rb>   phony target is a specified goal.

  rb> He also observed that in "force" targets this is usually the
  rb> situation. Another situation where this doesn't hold would be in those
  rb> cases where one tracing, profiling, or debugging code working by
  rb> instrumenting/augmenting the Makefile. Given this, I think the wording
  rb> above should be changed to something more akin to a heuristic or
  rb> guideline.

Hi; I'm certainly not adverse to changing the wording to be more clear,
but I'd like to understand what you mean first.

You say "[Bruno] also observed that in "force" targets this is usually
the situation" ... I didn't understand that comment?

Second, you discuss using .PHONY targets "where one tracing, profiling,
or debugging code working by instrumenting/augmenting the Makefile"; I
don't follow that either.  A mark of .PHONY is transitive: by that I
mean that if you mark a target as .PHONY then all the targets that
depend on that target are ALSO implicitly .PHONY; they will always be
rebuilt.

So, I don't see how it can be used for temporary measures like debugging
or tracing...?  Unless you mean editing the file to turn on/off the
.PHONY-ness; but in that case wouldn't it be simpler to just use -W or
similar?

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