DWARF 1 array bounds descriptors supported indicating an array of unknown
bounds. In DWARF 2, subrange type descriptors are used instead of array
bound descriptors, and no mechanism is defined for arrays of unknown
bounds.

DWARF 2 defines a missing bound value for a subrange to mean "default
value". It seems to me that an appropriate "default value" for the upper
bound in C/C++ would be "unknown"; this should be made explicit.

Editorial:  Reword comment in 5.10 to clarify that missing upper bound for an array indicates unknown
bound, rather than constant value.