A way of finding out what went wrong when a build fails

[bob racko]

I like the dump output from make - it contains a lot of good
stuff. Stuff I would like to see - but only if a recipe fails
in a way that is going to cause make to give up.

I am working on a huge build environment - so getting
a dump from every sub-make is not going to work.
It is non-interactive.

To complicate the constraints, -jN is used.

I would like to be selective about the dump output under certain conditions.

If I can avoid it - I would like to be able to specify the conditions without
having to pepper the makefiles with additional code.

Often I am just concerned about the current values of certain variables.
I know that Bmake has MAKE_PRINT_VAR_ON_ERROR for this.
Much of the code is contributed so I don't have the choice
of calling some other (potentially incompatible) make tool.

I can see that special variable being useful
along with a function like the one proposed in
http://lists.gnu.org/archive/html/help-make/2007-10/msg00004.html

However, the question remains how do I get the function or rule
to be called only if make is about to exit with failure?
Then there is the further issue of makefile peppering among
reams of contributed makefiles which I had hoped to avoid.

On occasion I want to see what rules or targets were being followed
as well as which sub make this was. I don't need to invent a new
programming language (from the many I already had to learn)
and jumping to an interactive debugger is not an option.

If this can be done without changes to make, please elucidate me
and I will apologize for taking your time.

If this requires a patch, I would like it if the patch were small
and not cause a rewrite of every puts()/printf(). I find
https://savannah.gnu.org/patch/?5362
to be too invasive.

Ok- so much for the requirements.
The nice part is I don't need help although I am enlisting
those on this list to see if perhaps adding further requirements
or desires will, in fact, simplify the implementation. I do desire
for the final result to become part of GNU make for everyone to use.

-bobr

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