andrew@rushmore.WV.TEK.COM (Andrew Klossner;685-2505;61-201;;frip) (08/24/89)
Under system V, cplus-lex.c has a cute hack that uses setvbuf to trick
stdio into treating a chunk of memory as a file, so that the lexer can
read characters from a stored inline function. But the hack is fragile
and breaks easily. A problem that I have encountered (while trying to
make the libg++ tests) is that, if the buffer given to setvbuf is
shorter than eight bytes long, setvbuf will (in violation of its man
page) ignore the buffer and call malloc to get a bigger one. The
comment in setvbuf, in vanilla system V release 3.2, says that stdio
needs at least eight bytes of slop because of synchronization problems
after signals.
I hacked the hack with a local copy of setvbuf that operates more
faithfully. But I think the "right" thing to do here is to lose the
hack, and move the switch between file input and inline-buffer input up
above the stdio abstraction. Mucking with the internals of a stdio
(*FILE) is impolite, and ironic when done in the name of a language
that champions strong data abstraction.
-=- Andrew Klossner (uunet!tektronix!frip.WV.TEK!andrew) [UUCP]
(andrew%frip.wv.tek.com@relay.cs.net) [ARPA]