Char / string Question

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  1. #1
    Supermassive black hole cboard_member's Avatar
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    Char / string Question

    Now I like the way C++ handles strings; I find parsing so much easier in every way.

    But...

    Here's the way I handle strings and such, a few code examples. I was just wondering if there's a more efficient way, or if I'm doing some n00b error type things.

    Code:
    #include <iostream>
    using namespace std;
    
    int main ()
    {
            char* buffer = new char[120];
            
            cout << "Enter a sentance: ";
            cin >> buffer;
    
            delete [] buffer;
            return 0;
    }
    A pretty useless example i know, but anyway...

    Code:
    #include <iostream>
    using namespace std;
    
    char* ret_buffer ()
    {
            char* buf = new char[50];
            return buf;
    }
    
    int main ()
    {
            char* buffer = new char[50];
    
            strcpy (buffer, ret_buffer(), 50);
            delete [] buffer;
            return 0;
    }
    And another.

    I was just wondering if there are any glaring mistakes? I just feel like I'm doing something wrong but can't put my finger on it. I have quarms about my second example where the function 'ret_buffer()' returns the pointer to a buffer (buf) which is never delete []'d.

    Any help appreciated .

    PS Please don't point out syntax errors I'll notice them after i've posted this and won't really care - we all know what it's supposed to do.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    The second one is returning a local variable . . . not good.
    dwk

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  3. #3
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    Code:
    #include <iostream>
    #include <string>
    
    using namespace std;
    
    int main()
    {
         string S1 = "my name is";
         cout << S1;
         S1 += " Petey Pablo!";
         cout << S1 << endl;
         cin.get();
         return 0;
    }
    Code:
    #include <iostream>
    #include <string>
    
    using namespace std;
    
    int main()
    {
         string userinput;
         cout << "Enter a string!  : ";
         getline(cin, userinput, '\n');
         cout << userinput;
         cin.get();
         return 0;
    }

  4. #4
    Registered User
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    Your qualms about the second example are correct. The memory you allocate in ret_buffer is never cleaned up, and you have a memory leak.

    BTW, that is how C handles strings. C++ handles strings with a string class that handles all the memory management for you so you don't have to worry about these things. Look up the C++ string class in the <string> standard header as ILoveVector's examples show.

    Also, the second one does not return a local variable, that statement is incorrect. It returns a pointer to dynamic memory, but that pointer is not saved and the memory is leaked.

  5. #5
    Supermassive black hole cboard_member's Avatar
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    I knew I was doing something wrong. I spelt qualms 'quarms'. Tutt. Summer heat.

    Thanks to all for your help!
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

  6. #6
    FOX
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    Quote Originally Posted by dwks
    The second one is returning a local variable . . . not good.
    I don't see any problem with that as long as you remember to save the return value to a new pointer. The allocated memory from new is not local.

  7. #7
    Supermassive black hole cboard_member's Avatar
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    Duly noted. Cheers.
    Good class architecture is not like a Swiss Army Knife; it should be more like a well balanced throwing knife.

    - Mike McShaffry

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