stdio line-streaming revisited

[Sean Kelly]

Andrei Alexandrescu (See Website For Email) wrote:
> 
> So what's the recommended use of Cout?
> 
> (a) If you do stdio, use Cout (and don't forget to flush Cout manually 
> every time you plan to read from Cin).

Oh right, this is what tie() is for with iostreams.  It's come up before 
in the past, though I can't recall if any conclusions were reached. 
I'll admit that the current behavior is a tad confusing here though.

> (b) But not for multithreaded programs that do stdio. For those, use the 
> logger facility. If you want multithreaded output to stdout, copy the 
> code from http://www.dsource.org/projects/tango/wiki/ChapterLogging into 
> your program. Be careful that that code might be incorrect; the manual 
> doesn't specify. If it is correct, be careful with what you do inside 
> that code, because you could deadlock yourself.

To be fair, this is mostly a documentation issue.  Though it may be that 
the logger could be made easier to use for your example.  I'll have to 
look at the logger in more detail before I say any more--I've only used 
it a handful of times.

> (c) And not for programs linking with anything that uses C's stdio. For 
> those, use Phobos.

Perhaps more accurately "programs that expect to mix output to the same 
device as linked libraries using C's stdio."  I can't recall ever 
needing this option, YMMV (and it obviously does).  One option might be 
to create a CStdioCondiuit or some such that uses C library calls 
instead of platform calls for IO.  Then the user could choose the 
appropriate one.

I think it's also perhaps worth noting that Tango is truly intended to 
be as much of an application framework as it is a collection of useful 
tools.  In fact, some non-essential features have been deliberately 
excluded to avoid discouraging third-party development.  I would also 
personally consider C stdio integration to be a specialized need for the 
typical D programmer, and therefore it is arguably not appropriate as 
the default configuration for Tango's IO layer if doing so incurs design 
or performance penalties (both of which seem to be the case, based on 
recent experimentation).  Therefore, I am not convinced that C 
integrated IO should be the default behavior for Tango's Cin/Cout, and 
feel it may be better offered as a separate conduit or handled some 
other way.  My opinion may well change if this proves to be a real issue 
for many people, but that's my gut feeling at the moment.


Sean