I always considered threads to be operating system oriented , where you can't simply "invade" the system inner processes and force them to execute code in a parallel fashion , you have to ask the OS to do so, if it's an allowed and given API.
Languages like Java have system-suited VM where they can implement threads in each OS using it's given API (as win32api , etc.).
just out of curiosity , how c++11, which has a portable code implements OS-independent threads?
They have a standardized memory model, and the standard library handles the wrapping of the OS-specific portions. This is exactly the same thing that Java and .Net do.
What can this strange device be?
When I touch it, it gives forth a sound
It's got wires that vibrate and give music
What can this thing be that I found?
Just like the new keyword is used to call operating system specific heap allocation routines, so thread library functions will call operating system specific functions to launch and handle threads.
C++ doesn't have a VM, so those operating system calls are part of the compiled executable. This is why C++ executables are not portable.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.
If you use dynamic linking the executable is portable as far as the standard library handling the OS calls because it will be linked in on whatever system you transfer the binary too. The reason it's not portable across systems like windows and linux is because the executable format itself is different on across those systems. The source is of course still portable though and can simply be recompiled on the new system to gain a locally compatible executable (or use cross-compiling on a single host).
So , as I can see it the C++ committee only implement the logic of the threads, and it's up to compiler developers to implement specific OS linking/compiling things?
I would wager, yes. This is in the same line of reasoning as King Mir and Elkvis.Originally Posted by Dave11
Heap allocations are OS-specific too so adding threads to the list is in the same ballpark.
That being said, I love, love, love C++11 for introducing std::thread and lambdas. It makes threading an application so simple I can't help but fall in love.
Yes. The committee only describes what shall happen and produces a document that describes that. It's up to the compiler developers and standard library developers to make sure that actually happens.
