🚀 go-pugleaf

Submitted-by: rfg@monkeys.com (Ronald F. Guilmette)

Greetings and happy new year.

I would like to know the exact semantics of the _IOFBF, _IOLBF, and
_IONBF mode flags for the `setvbuf' function (subclause 7.9.5.6 of the
ANSI/ISO C tandard).

Correct me if I'm wrong, but there doesn't seem to be any description
whatsoever of the semantics of these flags in the C standard.  Given
that, I rather wonder why these were standardized at all.  Certainly,
to just say ``Here are some possible flags for this function.  We don't
know what they do.'' doesn't help anybody.

What does the term ``full buffering'' mean?

What are the exact semantics of ``line buffering''?  In particular,
what is supposed to happen if I attempt (say, using fprintf) to write
a ``line'' to a given FILE where the length of the line exceeds the
size of the buffer currently associated with the given FILE?

What are the semantics of ``no buffering''?  In particular, what are
the implications for the traditional implementations of the getc and
putc macros of setting _IONBF for a given file?  Given that traditional
definitions of the getc and putc macros (including those which are still
in widespread use today) _assume_ buffering, should these macro defini-
tions be considered ``broken'' with respect to the ANSI/ISO C standard
in the presence of a call to setvbuf which uses _IONBF?  (For all you
POSIX 1003.1c aficionados out there note that this question also applies
equally to the new getc_unlocked and putc_unlocked functions.  Are the
current implementations of those ``broken'' too?)

-
-- Ron Guilmette, Roseville, CA -------- Infinite Monkeys & Co. ------------
---- E-mail: rfg@monkeys.com ----------- Purveyors of Compiler Test Suites -
------ Copyright (c) 1995 by Ronald F. Guilmette; All rights reserved. -----

[ Note the crossposting and Followup-To: line -- mod ]

Volume-Number: Volume 35, Number 75