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array values

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  • P Pryabu

    Hi, In the following code,i have assigned a value "test" to c variable. I have assigned the variable c to sz123. If i copied another value to c,the already assigend value in sz123[0] is getting overide. Can anyone please help me how to avoid this one? LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)c; strcpy(c,"123"); thanks,

    C Offline
    C Offline
    Cool_Dev
    wrote on last edited by
    #3

    you declared array of char pointers sz123 and stored the base adrress of string c to its 0th index. So whenever value in c changes, its reflected in sz123. If you want to store each strings in sz123, allocate memory for each.

    LPSTR sz123[10];

    char c[20] = "test";

    sz123[0] = new char[strlen(c)+1];
    strcpy(sz123[0], c);

    strcpy(c,"123"); //wont affect sz123[0]

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    • P Pryabu

      Hi, In the following code,i have assigned a value "test" to c variable. I have assigned the variable c to sz123. If i copied another value to c,the already assigend value in sz123[0] is getting overide. Can anyone please help me how to avoid this one? LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)c; strcpy(c,"123"); thanks,

      A Offline
      A Offline
      Aescleal
      wrote on last edited by
      #4

      Remember you're not really copying values around, you're copying pointers. So when you do:

      sz123[ 0 ] = c;

      You're just creating an alias to the block of memory that contains "hello." I'd suggest (unless you're stuck programming in C) to avoid using character arrays, character pointers and C style strings and just use C++ strings - then when you copy them around you're actually copying values and not aliases. Cheers, Ash

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      • P Pryabu

        Hi, In the following code,i have assigned a value "test" to c variable. I have assigned the variable c to sz123. If i copied another value to c,the already assigend value in sz123[0] is getting overide. Can anyone please help me how to avoid this one? LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)c; strcpy(c,"123"); thanks,

        CPalliniC Offline
        CPalliniC Offline
        CPallini
        wrote on last edited by
        #5

        sz123[0] = _strdup(c);
        //...
        free(sz123[0]);

        :)

        If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
        This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
        [My articles]

        In testa che avete, signor di Ceprano?

        P 1 Reply Last reply
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        • CPalliniC CPallini

          sz123[0] = _strdup(c);
          //...
          free(sz123[0]);

          :)

          If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
          This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
          [My articles]

          P Offline
          P Offline
          Pryabu
          wrote on last edited by
          #6

          Is it possible to use the globally declared LPSTR variable in other class by using extern function?

          CPalliniC 1 Reply Last reply
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          • P Pryabu

            Is it possible to use the globally declared LPSTR variable in other class by using extern function?

            CPalliniC Offline
            CPalliniC Offline
            CPallini
            wrote on last edited by
            #7

            Karthika85 wrote:

            Is it possible to use the globally declared LPSTR variable in other class by using extern function?

            You're mixing a bit different domains here. If the variable is global then you may use it everywhere (don't forget to call free when you no longer need the string). :)

            If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
            This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
            [My articles]

            In testa che avete, signor di Ceprano?

            P 2 Replies Last reply
            0
            • CPalliniC CPallini

              Karthika85 wrote:

              Is it possible to use the globally declared LPSTR variable in other class by using extern function?

              You're mixing a bit different domains here. If the variable is global then you may use it everywhere (don't forget to call free when you no longer need the string). :)

              If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
              This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
              [My articles]

              P Offline
              P Offline
              Pryabu
              wrote on last edited by
              #8

              No,I am not able to use the globally declared sz123[0] variable in another class: In class1: LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)malloc(sizeof(c[0]) * (strlen(c) + 1)); strcpy(sz123[0], c); In class2: extern LPSTR sz123[10]; char ch1[20]; strcpy(ch1,sz123[0]); It is showing the following error "error LNK2001: unresolved external symbol "char * * sz123":

              CPalliniC L 2 Replies Last reply
              0
              • CPalliniC CPallini

                Karthika85 wrote:

                Is it possible to use the globally declared LPSTR variable in other class by using extern function?

                You're mixing a bit different domains here. If the variable is global then you may use it everywhere (don't forget to call free when you no longer need the string). :)

                If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                [My articles]

                P Offline
                P Offline
                Pryabu
                wrote on last edited by
                #9

                Got it.I should not use static keyword to use in other cpp files

                CPalliniC 1 Reply Last reply
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                • P Pryabu

                  No,I am not able to use the globally declared sz123[0] variable in another class: In class1: LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)malloc(sizeof(c[0]) * (strlen(c) + 1)); strcpy(sz123[0], c); In class2: extern LPSTR sz123[10]; char ch1[20]; strcpy(ch1,sz123[0]); It is showing the following error "error LNK2001: unresolved external symbol "char * * sz123":

                  CPalliniC Offline
                  CPalliniC Offline
                  CPallini
                  wrote on last edited by
                  #10

                  You must be precise. A global variable cannot be declared inside a class (it wouldn't be global). So what do you intend to do? Do you want to use a global variable? Do you want to make an object's member variable available to objects of different classes? :)

                  If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                  This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                  [My articles]

                  In testa che avete, signor di Ceprano?

                  P 1 Reply Last reply
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                  • P Pryabu

                    Got it.I should not use static keyword to use in other cpp files

                    CPalliniC Offline
                    CPalliniC Offline
                    CPallini
                    wrote on last edited by
                    #11

                    Of course. The static qualifier, for varibles declared outside classes, makes the variables themselves having file-scope. :)

                    If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                    This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                    [My articles]

                    In testa che avete, signor di Ceprano?

                    1 Reply Last reply
                    0
                    • CPalliniC CPallini

                      You must be precise. A global variable cannot be declared inside a class (it wouldn't be global). So what do you intend to do? Do you want to use a global variable? Do you want to make an object's member variable available to objects of different classes? :)

                      If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                      This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                      [My articles]

                      P Offline
                      P Offline
                      Pryabu
                      wrote on last edited by
                      #12

                      I decalred a global variable array not class variable in one class and i want to use that gloabl variable in another class.

                      CPalliniC 1 Reply Last reply
                      0
                      • P Pryabu

                        I decalred a global variable array not class variable in one class and i want to use that gloabl variable in another class.

                        CPalliniC Offline
                        CPalliniC Offline
                        CPallini
                        wrote on last edited by
                        #13

                        And what's your problem? For instance:

                        // global.cpp
                        int global_counter=0;

                        and

                        // source.cpp
                        extern int global_counter;

                        void show_counter()
                        {
                        cout << global_counter << endl;
                        }

                        If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                        This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                        [My articles]

                        In testa che avete, signor di Ceprano?

                        P 1 Reply Last reply
                        0
                        • CPalliniC CPallini

                          And what's your problem? For instance:

                          // global.cpp
                          int global_counter=0;

                          and

                          // source.cpp
                          extern int global_counter;

                          void show_counter()
                          {
                          cout << global_counter << endl;
                          }

                          If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
                          This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
                          [My articles]

                          P Offline
                          P Offline
                          Pryabu
                          wrote on last edited by
                          #14

                          previously i used static keyword. so,i got that error. now i removed the keyword static.

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                          • P Pryabu

                            No,I am not able to use the globally declared sz123[0] variable in another class: In class1: LPSTR sz123[10]; char c[20] = "test"; sz123[0] = (LPSTR)malloc(sizeof(c[0]) * (strlen(c) + 1)); strcpy(sz123[0], c); In class2: extern LPSTR sz123[10]; char ch1[20]; strcpy(ch1,sz123[0]); It is showing the following error "error LNK2001: unresolved external symbol "char * * sz123":

                            L Offline
                            L Offline
                            Lost User
                            wrote on last edited by
                            #15

                            You need to declare it extern in all modules, and initialize it in only one.

                            It's time for a new signature.

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