Why would it be illegal to inform about “abort”?

Question

The GNU libc documentation of the abort function contains the following notice:

Future Change Warning: Proposed Federal censorship regulations may prohibit us from giving you information about the possibility of calling this function. We would be required to say that this is not an acceptable way of terminating a program.

Uh, what?

I found a seven-year-old Reddit thread discussing this. It appears that the notice was put in by Richard Stallman in 1995 — so it’s been in there for a while. However, except for a 1999 mailing list thread claiming it’s a joke, I couldn’t find any further information.

So: is this just an Easter egg put in by rms? Or is it serious (though probably no longer relevant)? If so, what does/did it refer to?

The Open Group POSIX documentation of the same function doesn’t include anything similar, nor do any of the man pages I consulted.

Answer 1

It is a reference to abortion gag laws, which forbid even mentioning abortion.

The Global Gag Rule was in place in the US in 1995-2009, was reinstated in 2017 and revoked again in 2021:

The “Global Gag Rule,” otherwise known as the Mexico City Policy, requires that any overseas organization receiving U.S. aid not have anything to do with abortion. Doctors, midwives, and nurses could not even mention the word abortion—much less provide abortion services with their own funds—even if it was legal in their country, or if a woman asks.

This is not directly related to software, but FSF has always been strongly opposed to all kinds of censorship legislation.

Answer 2

I would immediately assume it's a joke, yes.

My interpretation would be that it's some kind of reference to "abortion", i.e. stopping a pregnancy.