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https://www.lysator.liu.se/c/rat/title.html https://www.lysator.liu.se/c/rat/title.html has the C89 Rationale. “The terms unspecified behavior, undefined behav

• jcranmer 4y ago
  For the commentary on undefined behavior, I find N790 (https://www9.open-std.org/jtc1/sc22/wg14/www/docs/n790.htm https://www9.open-std.org/jtc1/sc22/wg14/www/docs/n790.htm) to be a better assessment of what the C committee thinks about undefined behavior: First consider the term "unspecified behavior". Most commentators on the Standard are of the opinion that this has the following properties: (1) There are a number of possible courses of actions, or the behavior is one that generates a result and then has a number of possible results. (2) The implementation can make any of the available choices, and can make different choices at different places or times. (3) The implementation need not document its choices. (4) No matter what choice the implementation makes, it cannot affect anything outside the range of that choice. If a value has to be chosen, it must be a valid value for that type. Property number 4 is the interesting one: it is usually taken to mean that the implementation cannot generate a spurious signal, branch to a random place in the code, or choose a trap representation. All of these, of course, are valid "undefined behavior".