eMake was invoked with an eMake root specification containing fewer entries than were used when the history file was generated.
The eMake history file records information about missing dependencies discovered while executing a build, for the purpose of improving performance in subsequent builds. The information is recorded as a series of eMake root relative paths, which enables the user to reuse the history file as long as the structure of the filesystem within the eMake roots is consistent from one build to the next, even if the absolute location of the build tree changes. Because the build may use multiple roots, the paths in the history file are specified as relative to a particular root identified by number; naturally if the number of roots used for the build changes, then the numeric identifier for each root may change, which will render eMake unable to match the information in the history file to the currently running build. Therefore, if the history file was generated by a build using a root specification with more entries than the current build has specified, eMake will display this warning.
Note that this message is a warning only, not an error. eMake will proceed to execute the build as expected. Performance may be impacted, but correctness will not be affected.
The user invoked eMake with an eMake root specification that contains fewer entries than the specification that was used when the history file was generated.