Compile only changed files when doing 'make'?

[Grant Edwards]

On 2022-01-25, Grant Edwards <grant.b.edwards at gmail.com> wrote:

> I'm working on a Renesas supplied port of U-Boot, and it seems that
> 'make' always compiles every single (configured) source file instead
> compiling only the source files that have been changed since the
> previous 'make'.

This problem appears to be caused by an incompatibility between the
Kbuild infrastructure2 and GNU make-4.3.  Switching to make-4.2.1
solved the problem.

The U-Boot source tree we're using is the v2017.01 branch. It's the
latest supported by the Renesas board support files.  I'm not very
happy they haven't contributed the supported upstream to make it
easier to support newer versions. I've asked Renesas about this, and
they have no plans to either support a newer version of U-Boot or
contribute their support files. :/

I assume that this Kbuild incompatibility with make-4.3 has been fixed
in newer versions of U-Boot.

If this Kbuild problem is familiar to anybody, and you know where the
fix was made, I'd appreciate a pointer so that I can back-port that
fix to my v2017.01 sources.

Thanks...

--
Grant