rms@AI.MIT.EDU (10/31/89)
3) There is no way that I can see to make "#pragma once" safe; that
is, a pragma in the sense defined in the ANSI C proposal.
The letter of the ANSI standard doesn't prohibit #pragma once. It may
be against the spirit, but that is not important. When ANSI specifies
a feature, that is a good reason to implement it as specified; when
ANSI does not specify a feature, that is not a strong reason to oppose
it.