Re: Make does not clean up the target when stderr is piped. Why?

[Paul Smith]

On Sat, 2021-06-05 at 23:00 +0900, Masahiro Yamada wrote:
>   make 2>&1 | tee build.log
> 
> is a very common use case, and people often miss to add  (trap "" 2;
> ...), I think.

Certainly.  It wasn't clear from your question what liberties you were
allowed to take with your environment.

I just explained what the problem was and gave a suggestion that would
resolve it without either modifying the make source code or modifying
your makefiles.

As Kaz points out, if you're using tee instead of cat you can use
tee -i (you can even make a shell alias like alias='tee -i' if you
like; I don't really see a downside to making this the default
behavior).

> I was wondering if I could take care of this in Makefile somehow.

Sure.  If you're willing to modify the makefile you have all kinds of
options.

Many build programs (like GCC and binutils for example) already have
built-in support for catching SIGINT and deleting output files
automatically, so they don't rely on make to do it for them in the
first place.  If the programs you're running don't do that, you have
two options:

First is to add a trap into the recipe, as you show.  I don't see why
it's necessary to detect whether or not you're writing to a pipe;
there's no harm in ALWAYS performing this cleanup regardless of
stdout/stderr.

> manual_cleanup = trap "rm -f $@; exit 130" INT;
> 
> build_command = echo hello > $@; sleep 10; echo bye >> $@
> 
> test.txt:
>         $(manual_cleanup)$(build_command)

The other option which is often used for commands which don't have
their own SIGINT handling is to generate the output into a temporary
file and rename it only as the last step.  Renames (to the same
filesystem) are typically atomic so you either get the new version or
not, like this:

  test.txt:
          rm -f $@; echo hello > $@.tmp; sleep 10; echo bye >> $@; \
          mv -f $@.tmp $@;