This warning indicates that the named history file is invalid. The build proceeds as if no history file is available, so the build may run longer than expected due to conflicts, but correctness is unaffected.
The Electric Make (eMake) history file consists of several plain-text sections. One of these is the serial-deps section, which enumerates the discovered dependencies in the build using a simple encoding consisting of lists of indexes into the makes and jobs sections. Message EC1043 indicates that there was an error processing the serial-deps section. Generally this means that the history file is corrupt or truncated.
The best way to eliminate this warning is to generate a new history file
by running the build to completion. eMake automatically generates a new,
properly formatted history file when the build finishes as long as the
--emake-history mode is either merge (the default if nothing is
specified) or create.
--emake-history mode is read, then eMake does not replace the
history file automatically. In that case you must rerun the build with
--emake-history set to merge or create.
You may also eliminate this warning by deleting the invalid history file, but you will still have to generate a new history file for the build in this case.