Subj : Re: Thoughts about threads in C++
To   : comp.programming.threads
From : Maciej Sobczak
Date : Thu May 26 2005 11:10 am

Hi,

partow@gmail.com wrote:

> Try this C++ library, I will give you directions
> on how to create and use threads in a c++ context.

In this thread (no pun intended) I claimed that the existence of threads 
should be acknowledged at the level of control statements and that the 
library approach will be always flawed in one way or another.

> http://www.partow.net/programming/posixsynchwrapper/index.html

This is a library.

The Java-like approach (when you have to inherit from some Thread 
interface and pretend that your class Is_A thread) is indeed quite 
popular. I don't think, however, that this is the best you can get.

Few comments considering your code:

1. You use explicit lock and unlock calls in your example code. This is 
not really C++.

2. The POSIXThread base class is copyable, but its copy constructor and 
assignment operator do nothing, not even copy the thread id (so the 
comparison operators are broken). You also use copyable derived thread 
classes in one of the example (you put them into the vector). I'm not 
sure whether this is really what you want to do (for example: can I join 
the copy of the original thread?).

3. The class POSIXScopeMutex makes no sense at all - how do you want to 
use it from multiple threads?

4. The POSIXCondition class contains *both* the condvar and the mutex as 
members. Is there any gain from doing this? Moreover, the wait() method 
takes no parameters. How can I wait for some *condition* (instead of 
just "signal") to take place?

5. Coming back to the POSIXThread base class, it contains the static 
member which is used as a thread start routine. This may not compile on 
some platforms, since class members (even if static) cannot be made 
extern "C".

I don't claim that this list is complete. ;)

-- 
Maciej Sobczak : http://www.msobczak.com/
Programming    : http://www.msobczak.com/prog/

.