Howard Chu writes:

OK, you're right, it's trivial, and I see that the configure script already #defines sig_atomic_t to int if the system doesn't already define it. So your suggested changes are harmless, go ahead and make them. If you're going to that trouble, you should change gotintr to use an explicitly defined contiguous range of values.

OK, later.. that's why I filed an its first (in particular, need to look at WAKE_LISTENER first.)

Which makes the rest of this reply irrelevant to the ITS, so skip it if that helps your blood pressure:

Backward compatibility only reinforces my point, since int has always been atomic in the past.

Where do you get that from? A brief search find nothing like that in the draft and standard versions I've lying around. It would also mean that sig_atomic_t would be a pointless type.

...

Otherwise the standard would not have needed to define sig_atomic_t.

Note that sig_atomic_t is an *optional* part of the standard; implementations are not required to provide it.

Irrelevant. Freestanding implementations need not provide it (nor most of the rest of the C library), but <signal.h> requires it.

The standard says it is impossible for arithmetic operations on valid values to generate trap representations. Think about it - if it were *possible* for intermediate states to be invalid, (...)

A signal breaks the rest of the execution model. A variable need not be in an "intermediate state" according to that model when a signal arrives. Otherwise C could not use *any* inherently non-atomic types, which would rather limit which CPUs could support C. That's why the standard says signal handlers can do so aburdly few things in the first place.

Nobody is stupid enough to design a machine like that, and the standard guarantees that programmers never have to worry about such a stupidity ever existing. (...) Not on any machine ever built (for which a C translator exists).

On the countrary, the existence of such hosts is precicely why the section about signal handlers explicitly contradicts you. And as Doug Gwyn said, even the little part it does guarantee was hard to get agreement for.