On Thu, 2021-12-23 at 12:49 +0000, Zhu, Mason wrote: > In GNU Make 3.82, it seems that -j option will be finally added if > Make determines my VM has the parallel build capability.
It has never been the case that any version of GNU make has automatically enabled parallel builds by itself. It's always been required that the user request it via the -j option. If you are seeing parallelism in 3.82 then someone provided -j on the command line or in MAKEFLAGS before starting make. I don't believe that GNU make 3.82 allows -j to be added to MAKEFLAGS inside the makefile and take effect in the current invocation of make. > However in GNU Make 4.2.1, there is no parallel build if I does not > explicitly set -jN option. Does this mean that you discovered a way to make parallel builds work as expected using GNU make 4.2.1? Just by adding this argument? Exactly how did you do this? If so we'll need to fully understand how you are enabling parallel builds in GNU make 3.82 and what change you made to make it work in GNU make 4.2.1.
