Re: GNU make troubleshooting

[Alejandro Colomar]

Hi Bruno, Paul,

On 7/10/23 21:41, Bruno Haible wrote:
> Paul Smith wrote:
> > Showing the "macroexpanded make sources" is difficult because make
> > doesn't just expand an entire line then parse it.  Makefile syntax is
> > context-sensitive so you can't know how or if to expand parts of a line
> > until you've already expanded other parts.  Of course make could keep
> > track of this for generating this kind of output.
>
> If no perfect solution to this problem is possible, how about
> implementing a simple approximation first, and then improve it based
> on user feedback?
>
> Because how is a GNU make user supposed to understand a Makefile and
> the expansion of things like
>
>     $(1): $$($(1)_OBJS) $$($(1)_LIBS:%=-l%)
>
> or
>
>     $(objpfx)$o$($o-version): $(objpfx)$o; $$(make-link)
>
> if 'make' does not help them? [1]

My approach to debugging has always been fprintf(3) with C programs, as
I find debuggers too complex for what I need.  When debugging GNU
Makefiles, I have a similar approach, and it usually works.  I need some
intuition to know where to place the statements, but after a few tries,
I usually find the bug.  In GNU Make, the "printf" statement is the
$(info ...) function.  Maybe you didn't know about it?

So, I usually add a few of them before suspicious lines.  It could be:

$(info DBG: $(1))
$(info DBG: $$($(1)_OBJS))
$(info DBG: $$($(1)_LIBS:%=-l%))
$(info DBG: $$($(1)_LIBS))
$(1): $$($(1)_OBJS) $$($(1)_LIBS:%=-l%)

That should solve most of your doubts, doesn't it?

Cheers,
Alex


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