[RFC] libstdc++/10063: stdio_filebuf broken

[Paolo Carlini <pcarlini at unitus dot it>]

Hi everyone.

I'd like to ask your opinion about this PR. I briefly recall you
that, presently, due to the low level use of non-blocking syscalls
in basic_filebuf, stdio_filebuf is broken, in the sense that its
use cannot be really intermixed with stdio.

For 3.4 I see only two options:

1* Rip it out completely. Indeed, stdio_sync_filebuf should be really
used now for the purposes which originally led to the ext::stdio_filebuf
extension. As regards the internal uses of stdio_filebuf (in ios.cc, I
mean, of course) its should be not difficult to use directly basic_filebuf.

2* Option 1* above + a reimplementation stdio_filebuf using underlying C
library calls, to be provided to the users for backward compatibility with
past code using this extension.

In case we think we really need 2*, this means we can do the 1* part only
/after/ having completed the reimplementation. Probably I /could/ still do
the work in time for 3.4, anyway... it's mostly cut and paste...

Ideas?

Paolo.