🚀 go-pugleaf

People have correctly pointed out that "undefined behaviour" allows
the program to execute the "halt and catch fire" instruction, declare
Armageddon, or anything else.

But your other meaning "return an undefined value" also exists in the
standard, as does "return a valid but undefined value" (which is not
the same), and "return an undefined member of a set of defined values".
If I remember correctly, I found at least two and possibly three other
possibilities when I studied this area.

However, these extra categories are rarely (if ever) CALLED "undefined"
in the standard.  The standard uses the term "undefined" in a specific
way, and uses other phraseologies to describe the other possibilities.
If you find an exception to this, it is probably an error in the
wording of the standard.


Nick Maclaren,
University of Cambridge Computer Laboratory,
New Museums Site, Pembroke Street, Cambridge CB2 3QG, England.
Email:  nmm1@cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679