Re: make: warn about fallback from parallel to compat mode

["Simon J. Gerraty" <sjg%juniper.net@localhost>]

Christoph Badura <bad%bsd.de@localhost> wrote:
> On Sun, May 25, 2025 at 10:18:36AM -0700, Simon J. Gerraty wrote:
> > Roland Illig <roland.illig%gmx.de@localhost> wrote:
> > > The attached patch warns about cases like this. The warning is quite
> > > verbose, but I didn't manage to make it shorter without sacrificing
> > > understandability.
> >
> > Including .CURDIR is a good improvement.
> 
> Looks to me like this is not at all that useful.  See the log below from a
> build I ran this afternoon.
> 
> Maybe .PARSEDIR/.PARSEFILE would be more appropriate?  The idea is that I'd
> like to know which line in which makefile is the offending one.  Referring
> to random directories that don't even contain Makefiles is not actually
> helpful.

Note that the make instance reporting the issue has no clue about what
makefile the parent was reading, and none of the makefiles it is reading
(if any) are necessarily relevant.  .CURDIR probably is the best clue
available.
 
> Also, wasn't the message supposed to get shortened?  This turns out to be
> quite spammy.

Yes that was my initial reaction too.
Given you should see it very rarely, I can live with it.
A cryptic error that does nothing to help track down the origin is no
help.
A reference to a specific sub-section in make(1) would be a good option.
Eg. something like?

Errors
     Some errors or warnings reported by make require explaination.

     Rather than have make output voluminous descriptions, it can refer to
     this section of the manual.

     -J      This is an internal flag passed in the environment variable
             MAKEFLAGS.  It communicates the file descriptors for accessing
             the job token pipe.  If in jobs mode, make finds that the
             descriptors referenced are not valid, it will drop to
             compatibility mode.

             Adding the -B option or setting .MAKE.MODE to `compat' lets make
             know it is supposed to be in compatibility mode and no warning
             will be issued.



Then make could just give a warning like

nbmake[2]: warning: internal option "-J" in "${.CURDIR}" refers to
unopened file descriptors; falling back to compat mode.
Refer to '-J' in make(1) Errors section.