If strings are missing (e.g. because the last value of a range changed
unknowingly or adding a string was simply forgotten) compilation will
now fail.
This could be problematic if the upper limit is out of our control (e.g.
from a system header like pfkeyv2.h), in which case patches might be
required on certain platforms (enforcing at least, and not exactly, the
required number of strings might also be an option to compile against
older versions of such a header - for internal enums it's obviously
better to enforce an exact match, though).
Handling the result for enum_from_name() is difficult, as checking for
negative return values requires a cast if the enum type is unsigned. The new
signature clearly differentiates lookup result from lookup value.
Further, this actually allows to convert real -1 enum values, which could not
be distinguished from "not-found" and the -1 return value.
This also fixes several clang warnings where enums are unsigned.
Tobias Brunner