#pragma does only half the job (was Re: Pragma and noalias)

[Henry Spencer]

>... implementation defined means that you can change only a
>very limited subset of things, i.e., those things labeled as
>implementation defined in the standard...

Please justify this with specific citations from X3J11.  I spent quite a
while examining the precise semantics of #pragma when I was arguing with
Doug about this; I recall nothing that would support this interpretation.
The words (2ndP.C. draft) are "causes the implementation to behave in an
implementation-defined manner".  The definition of "implementation-defined"
just says that it depends on the implementation and must be documented.
Even the original GNU CC semantics -- in which recognition of a #pragma
causes the compiler to try to start one of the usual Unix interactive game
programs -- is technically legitimate, albeit unfriendly.

The fact is that the whole effect of a #pragma is implementation-defined,
and the draft does not specify whether it is allowed to alter the language
semantics.  Either interpretation is self-consistent.
-- 
Anyone who buys Wisconsin cheese is  |  Henry Spencer @ U of Toronto Zoology
a traitor to mankind.  --Pournelle   | {ihnp4,decvax,uunet!mnetor}!utzoo!henry