[Scons-users] Bug MD5-timestamp and --debug=explain

[Mats Wichmann]

On 6/3/20 3:46 AM, orenaud at coventor.com wrote:
> Hi,
> 
> I observe a strange behavior of --debug=explain, when the MD5-timestamp
> decider is used. When I change a single file, --debug=explain marks all
> the "sibling" dependencies as "changed". It does not affect the build
> itself though, as expected only the necessary files are recompiled.

this isn't much of an answer, just sort of an ack to your ping...

I see the same on a Linux system with your test. There's a testcase that
should trigger this:

test/Decider/MD5-timestamp-explain.py

but it doesn't, because it doesn't use an external command whose
signature would thus be included in the implicit dependencies, it uses
Copy().


There have been a few issues with explain() not explaining very well.

Fortunately (and as you've apparently surmised, as you've noted it
doesn't impact the build), the explain function is completely separate,
if you've asked for debugging at this level, and the decider decides a
rebuild is needed, only then is it called, and it does its own
calculations in preparing the messages eventually output.