stdio performance in tango, stdlib, and perl

[Andrei Alexandrescu (See Website For Email)]

Walter Bright wrote:
> Sean Kelly wrote:
>> There really isn't any way to do automatic locking with chained opCall 
>> barring the use of proxy objects or something equally nasty. Also, it 
>> hurts efficiency to always lock regardless of whether the user is 
>> performing IO in multiple threads.  The preferred method here is:
>>
>> synchronized( Cout )
>>     Cout( a )( b )( c )();
> 
> The trouble with that design is people working on subsystems or 
> libraries, which will be combined by others into a working whole. Since 
> it is extra work to add the synchronized statement, odds are pretty good 
> it won't happen. Then, the whole gets erratic multithreading performance.
> 
> Ideally, things should be inverted so that thread safety is the default 
> behavior, and the extra-efficiency-dammit-I-know-what-I'm-doing is the 
> extra work.
> 
> One way to solve this problem is to use variadic templates as outlined 
> in http://www.digitalmars.com/d/variadic-function-templates.html
> 
> Back in the early days of Windows NT, when multithreaded programming was 
> introduced to a mass platform, C compilers typically shipped with two 
> runtime libraries - a single threaded one "for efficiency", and a 
> multithreaded one. Also, to do multithreaded code, one had to predefine 
> _MT or throw a command line switch. Inevitably, this was overlooked, and 
> endless bugs consumed endless time. I made the decision early on to only 
> ship threadsafe libraries, and have _MT always on. I've never regretted 
> it, I'm sure it saved me a lot of tech support time, and avoided the 
> perception that the compiler didn't work with multithreading.

MS does the same now if I remember correctly: all of its libraries are 
MT by default.

I agree with Walter's sentiment that Cout(a)(b) is a design mistake. 
Fortunately, now we have compile-time variadic functions, which will 
make it easy to correct the design - Cout(a, b) can be made just as good 
without having to chase typeinfo's at runtime.


Andrei