Calling other objects methods inside a constructor

This is a discussion on Calling other objects methods inside a constructor within the C++ Programming forums, part of the General Programming Boards category; If I have this code Code: File 1: typedef class c_Semaphore { public : c_Semaphore() { if (sem_init(&sem, 0,0)) Log.Error("Error ...

  1. #1
    Alessio Stella
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    Thumbs up Calling other objects methods inside a constructor

    If I have this code

    Code:
    File 1:
    
    typedef class c_Semaphore
    {
    public :
    c_Semaphore() 
    {
         if (sem_init(&sem, 0,0)) Log.Error("Error in semaphore init (constructor)");
    }
    ~c_Semaphore()	{	sem_destroy(&sem);	}
    	sem_t  sem;	
    } Type_Semaphore;
    
    Type_Semaphore Sem;
    
    
    File 2 :
    typedef class c_Log
    {
    public :
       ...
       void Error(const char * ch) {..}
    } Type_Log;
    
    Type_Log Log;
    Would you suppose that the compiler+linker is sufficiently fine to call c_Log constructor for object Log and after the constructor for Sem or , as they are in different modules, the compiler+linker gives errors or does not garauntee the correct order in constructor callings?

    thank you
    Last edited by mynickmynick; 09-17-2008 at 03:41 AM.

  2. #2
    Kernel hacker
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    I do not think you can rely on Log being constructed before Sem.

    Log looks like something that could be implemented using a Singleton pattern, so you may not need a constructor as such.

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Alessio Stella
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    Quote Originally Posted by matsp View Post
    I do not think you can rely on Log being constructed before Sem.

    Log looks like something that could be implemented using a Singleton pattern, so you may not need a constructor as such.

    --
    Mats
    What is a singleton pattern?
    Log is a cyclic buffer where to write by multiple threads, which periodically is saved to a log file or sent via socket to a client log

  4. #4
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    google gives this:
    http://en.wikipedia.org/wiki/Singleton_pattern
    which is a much more complete explanation than what I can give. (But in short, it is an object that may have may instances that is represented behind the scenes by a single object).

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
    Cat without Hat CornedBee's Avatar
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    There's no guaranteed order of initialization between globals of different modules.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  6. #6
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    Quote Originally Posted by CornedBee View Post
    There's no guaranteed order of initialization between globals of different modules.
    So, presumably the two global objects could be put in a "globals.cpp" or "main.cpp" and the order of the objects themselves would define the order of initialization.

    This is of course not a very natural way to solve the problem, but it IS a possibility - the biggest problem comes when you have hundreds of different modules with various global objects, in which case wrapping the object into something that can perform it's initialization as needed is the right solution, such as the singleton pattern. [There are other solutions that do similar things, but they all rely on "if this is not set, create an object, else return the existing object"].

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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