[bug #57575] --load-average changes order or jobs

[Andre Heider]

URL:
  <https://savannah.gnu.org/bugs/?57575>

                 Summary: --load-average changes order or jobs
                 Project: make
            Submitted by: aheider
            Submitted on: Fri 10 Jan 2020 05:23:38 PM UTC
                Severity: 3 - Normal
              Item Group: Bug
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: 4.2.1
        Operating System: POSIX-Based
           Fixed Release: None
           Triage Status: None

    _______________________________________________________

Details:

When using -l, it seems the order of jobs is different compared to not using
-l.

For some projects, this difference is enough to break the build. 

For the cases where I observed this, it was always a bug in a Makefile.
Examples are GNU screen and bash. Both projects create a header using a make
rule, with missing dependencies for the files including it.
Another example is MAME, where the directory for a to-be created object file
was not created in time (missing " | $(OBJDIR)")

Building those projects without -l always succeeds.

For distros, which compile many packages in parallel, -l is a gift, but breaks
random packages too easily. Is it possible to not change the behavior when
using -l?

I can easily reproduce this locally (8 core box) with GNU screen 4.6.2 using
make 4.2.1 or 4.2.93:
./configure
while true; do make clean; make -j8 -l0.5 || break; done
...
screen.h:48:10: fatal error: comm.h: No such file or directory




    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?57575>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/