Programming: Windows Threading Vs Linux Threading (Part 2)

This is in continuation of the previous article 'Windows Threading Vs. Linux Threading', here we'll see a subtle but significant difference in the thread start routine which gets a call from CreateThread() API in the Windows world or pthread_create() function call in the Linux world.

The ThreadProc function in Windows:

DWORD WINAPI ThreadProc(
_In_ LPVOID lpParameter
);

This is an application-defined function that serves as the starting address for a thread.

Note: As per MSDN, Do not declare this callback function with a void return type and cast the function pointer to LPTHREAD_START_ROUTINE when creating the thread.
Code that does this is common, but it can crash on 64-bit Windows.

The return value indicates the success or failure of this function. The return value should never be set to STILL_ACTIVE (259).

In Linux: The function passed as start_routine in the pthread_create() function should correspond to the following C function prototype:
void *threadStartRoutinName(void *);

This is one of the differences we need to take care of while writing thread start routines between Windows and Linux.

Comments

Reversing char array without splitting the array to tokens

I was reading about strdup, a C++ function and suddenly an idea came to my mind if this can be leveraged to aid in reversing a character array without splitting the array into words and reconstructing it again by placing spaces and removing trailing spaces. Again, I wanted an array to be passed as a function argument and an array size to be passed implicitly with the array to the function. Assumed, a well-formed char array has been passed into the function. No malformed array checking is done inside the function. So, the function signature and definition are like below: Below is the call from the client code to reverse the array without splitting tokens and reconstructing it. Finally, copy the reversed array to the destination. For GNU C++, we should use strdup instead _strdup . On run, we get the following output: Demo code

A simple approach to generate Fibonacci series via multi-threading

T his is a very simple approach taken to generate the Fibonacci series through multithreading. Here instead of a function, used a function object. The code is very simple and self-explanatory. #include <iostream> #include <mutex> #include <thread> class Fib { public: Fib() : _num0(1), _num1(1) {} unsigned long operator()(); private: unsigned long _num0, _num1; std::mutex mu; }; unsigned long Fib::operator()() { mu.lock(); // critical section, exclusive access to the below code by locking the mutex unsigned long temp = _num0; _num0 = _num1; _num1 = temp + _num0; mu.unlock(); return temp; } int main() { Fib f; int i = 0; unsigned long res = 0, res2= 0, res3 = 0; std::cout << "Fibonacci series: "; while (i <= 15) { std::thread t1([&] { res = f(); }); // Capturing result to respective variable via lambda std::thread t2([&] { res2 = f(); }); std::thread t3(

Close a Window Application from another application.

This is just a demo application code to show how the WM_CLOSE message can be sent to the target process which has a titled window to close the application. To achieve this, either we can use SendMessage or PostMessage APIs to send required Windows messages to the target application. Though both the APIs are dispatching WM_XXXXX message to target application two APIs has some differences, these are as below: 1. SendMessage () call is a blocking call but PostMessage is a non-blocking call(Asynchronous) 2. SendMessage() APIs return type is LRESULT (LONG_PTR) but PostMessage() APIs return type is BOOL(typedef int). In Short, SendMessage () APIs return type depends on what message has been sent to the Windowed target process. For the other one, it's always a non-zero value, which indicates the message has been successfully placed on the target process message queue. Now let's see how can I close a target windowed application "Solitaire & Casual Games" from my custom-

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