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quick question

This is a discussion on quick question within the C Programming forums, part of the General Programming Boards category; Hey everyone could someone tell me why the first code is working(without functions) and the second one is not? Code: ...

  1. #1
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    quick question

    Hey everyone could someone tell me why the first code is working(without functions) and the second one is not?
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    int main (void)
    {
      int row_size1,col_size1,row_size2,col_size2,flag =1;
      int **A;
      int i = 0, j = 0;
      char a,c;
    
    
    do
      {
        A = malloc(2 * sizeof (int *));
    
    printf("\ncmd> ");
    c = getchar();
    
    if(c == 'A')
     {
    
    scanf("%d %d",&row_size1,&col_size1);
    
    A[0]= malloc(row_size1*sizeof(int*));
    
    for(i=0;i<row_size1;i++)
       {
           A[i]=malloc(col_size1*sizeof(int));
            }
    
    for(i=0;i<row_size1;i++)
         {
             for(j=0;j<col_size1;j++)
                  {
                    scanf("%d",&A[i][j]);
                    // if (A[i][j] == 99) // 'x' is character variable i declared
                         // break;
                  }
              }
    
    printf("The required matrix is\n");
    for(i=0;i<row_size1;i++)
        {
           for(j=0;j<col_size1;j++)
                printf("%d ",A[i][j]);
                printf("\n");
              }
    
    for(i=0;i<row_size1;i++)
         {
            free(A[i]);
              }
    free(A);
          
    }
    
    
    if(c == 'B')
    {
    scanf("%d %d",&row_size1,&col_size1);
    
    A[1]= malloc(row_size1*sizeof(int*));
    for(i=0;i<row_size1;i++)
        {
           A[i]=malloc(col_size1*sizeof(int));
              }
    
    for(i=0;i<row_size1;i++)
        {
           for(j=0;j<col_size1;j++)
                {
                    scanf("%d",&A[i][j]);
                    if (A[i][j] == 99) // 'x' is character variable i declared
                      break;
                  }
              }
    
    printf("The required matrix is\n");
    for(i=0;i<row_size1;i++)
        {
           for(j=0;j<col_size1;j++)
                printf("%d ",A[i][j]);
                printf("\n");
              }
    
    for(i=0;i<row_size1;i++)
         {
            free(A[i]);
              }
    free(A);
     }
     }
    
    while(flag == 1);
    return 0;
    }
    same code using functions
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    
    
    int main (void)
    {
      int row_size1,col_size1,row_size2,col_size2,flag =1;
      int **A=NULL;
      int i = 0, j = 0;
      char a,c;
    
    
    
    
    
    
    do
      {
        A = malloc(2 * sizeof (int *));
    
    
        printf("\ncmd> ");
        c = getchar();
    
    
        if(c == 'A')
          {
    
    
      scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
      A[0]= malloc(row_size1*sizeof(int*));
      for(i=0;i<row_size1;i++)
        {
          A[i]=malloc(col_size1*sizeof(int));
        }
    
    
    
    
    for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            {
              scanf("%d",&A[i][j]);
     }
        }
     matrix_display(A[0], row_size1, col_size1);
          }
     if(c == 'B')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[1]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[i]=malloc(col_size1*sizeof(int));
           }
    
    
    
    
         for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[1], row_size1, col_size1);
     }
      }
     while(flag == 1);
    //return 0;
    }
    
    
    void matrix_display(int *A, int row_size1, int col_size1)
    {
      int i,j;
      printf("The required matrix is\n");
      for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            printf("%d ",A[i][j]);
          printf("\n");
        }
      for(i=0;i<row_size1;i++)
        {
          free(A[i]);
        }
      free(A);
    }
    Last edited by zafy; 11-15-2012 at 06:42 AM.

  2. #2
    and the hat of wrongness Salem's Avatar
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    The first one might 'work', but it's still broken none the less.
    Code:
    $ valgrind ./a.out
    ==4438== Memcheck, a memory error detector
    ==4438== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
    ==4438== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
    ==4438== Command: ./a.out
    ==4438== 
    
    cmd> A 3 2
    ==4438== Invalid write of size 8
    ==4438==    at 0x400786: main (bar.c:26)
    ==4438==  Address 0x51d2050 is 0 bytes after a block of size 16 alloc'd
    ==4438==    at 0x4C28F9F: malloc (vg_replace_malloc.c:236)
    ==4438==    by 0x4006FB: main (bar.c:14)
    ==4438== 
    1 2 3
    4 5 6
    ==4438== Invalid read of size 8
    ==4438==    at 0x4007B4: main (bar.c:31)
    ==4438==  Address 0x51d2050 is 0 bytes after a block of size 16 alloc'd
    ==4438==    at 0x4C28F9F: malloc (vg_replace_malloc.c:236)
    ==4438==    by 0x4006FB: main (bar.c:14)
    ==4438== 
    The required matrix is
    1 2 
    3 4 
    ==4438== Invalid read of size 8
    ==4438==    at 0x40081A: main (bar.c:40)
    ==4438==  Address 0x51d2050 is 0 bytes after a block of size 16 alloc'd
    ==4438==    at 0x4C28F9F: malloc (vg_replace_malloc.c:236)
    ==4438==    by 0x4006FB: main (bar.c:14)
    ==4438== 
    5 6 
    ==4438== Invalid read of size 8
    ==4438==    at 0x400878: main (bar.c:45)
    ==4438==  Address 0x51d2050 is 0 bytes after a block of size 16 alloc'd
    ==4438==    at 0x4C28F9F: malloc (vg_replace_malloc.c:236)
    ==4438==    by 0x4006FB: main (bar.c:14)
    ==4438== 
    
    cmd>
    Look at this code.
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    int main(void)
    {
      int row_size1, col_size1, row_size2, col_size2, flag = 1;
      int **A[2];
      int i = 0, j = 0;
      char a, c;
    
    
      do {
    //    A = malloc(2 * sizeof(int *));
    
        printf("\ncmd> ");
        c = getchar();
    
        if (c == 'A') {
    
          scanf("%d %d", &row_size1, &col_size1);
    
          A[0] = malloc(row_size1 * sizeof(int *));
          for (i = 0; i < row_size1; i++) {
            A[0][i] = malloc(col_size1 * sizeof(int));
          }
    
          for (i = 0; i < row_size1; i++) {
            for (j = 0; j < col_size1; j++) {
              scanf("%d", &A[0][i][j]);
              // if (A[i][j] == 99) // 'x' is character variable i declared
              // break;
            }
          }
    
          printf("The required matrix is\n");
          for (i = 0; i < row_size1; i++) {
            for (j = 0; j < col_size1; j++)
              printf("%d ", A[0][i][j]);
            printf("\n");
          }
    
          for (i = 0; i < row_size1; i++) {
            free(A[0][i]);
          }
          free(A[0]);
        }
      }
    
      while (flag == 1);
      return 0;
    }
    If you want, you can start with
    int ***A;
    and
    A = malloc( 2 * sizeof(int**) );
    to replace the array of 2 elements.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  3. #3
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    Oh I thought the first one was perfect but thanks

    but why isn't the second one even compiling? I tried the int ***A

    but i honestly thought that this line
    Code:
    A = malloc( 2 * sizeof(int**) );
    

    just tells the program I am allocating space for 2 matrices A and B

  4. #4
    and the hat of wrongness Salem's Avatar
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    Well if you turned everything into pointers, then you need

    void matrix_display(int **A, int row_size1, int col_size1)
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  5. #5
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    is this what you mean?
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    
    
    int main (void)
    {
      int row_size1,col_size1,row_size2,col_size2,flag =1;
      int **A=NULL;;
      int i = 0, j = 0;
      char a,c;
    
    
    
    
    
    
    do
      {
        A = malloc(2 * sizeof (int **));
    
    
        printf("\ncmd> ");
        c = getchar();
    
    
        if(c == 'A')
          {
    
    
      scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
      A[0]= malloc(row_size1*sizeof(int*));
      for(i=0;i<row_size1;i++)
        {
          A[0][i]=malloc(col_size1*sizeof(int));
        }
    
    for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            {
              scanf("%d",&A[0][i][j]);
              //      if (A[i][j] == 99) // 'x' is character variable i declared
                        // break;
            }
        }
     matrix_display(A[0][i][j], row_size1, col_size1);
          }
     if(c == 'B')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[1]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[1][i]=malloc(col_size1*sizeof(int));
           }
    
    
    
         for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[1][i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[1][i][j], row_size1, col_size1);
     }
      }
     while(flag == 1);
    }
    
    
    void matrix_display(int **A, int row_size1, int col_size1)
    {
      int i,j;
      printf("The required matrix is\n");
      for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            printf("%d ",A[i][j]);
          printf("\n");
        }
      for(i=0;i<row_size1;i++)
        {
          free(A[i]);
        }
      free(A);
    }

  6. #6
    and the hat of wrongness Salem's Avatar
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    No, nothing like what I meant.

    int ***A;

    A is a pointer to a number of matrices
    A[0] is a pointer to the first matrix
    A[0][0] is a pointer to the first row of the first matrix.


    To display one of the matrices, you would do
    matrix_display(A[1], row_size1, col_size1);

    I suggest you prototype the function before calling it, then you would get some useful diagnostics.
    Though TBH, I can't see how this compiles at all without a great deal of complaining from the compiler.

    FWIW, matrix_display seems good now, if you can figure out how to call it properly.

    Perhaps you should start with
    int **A[2];
    and get that working properly, before trying to allocate something for int ***A;
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  7. #7
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    please tell me this is what you mean
    way too many warnings!
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    void matrix_display(int *matrix, int row_count, int column_count);
    
    
    
    
    int main (void)
    {
      int row_size1,col_size1,row_size2,col_size2,flag =1;
      int **A[2];
      int i = 0, j = 0;
      char a,c;
    
    
    
    
    
    
    do
      {
        A = malloc(2 * sizeof (int **));
    
    
        printf("\ncmd> ");
        c = getchar();
    
    
        if(c == 'A')
          {
    
    
      scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
      A[0]= malloc(row_size1*sizeof(int*));
      for(i=0;i<row_size1;i++)
        {
          A[0][i]=malloc(col_size1*sizeof(int));
        }
    
    
    
    
    for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            {
              scanf("%d",&A[0][i][j]);
              //      if (A[i][j] == 99) // 'x' is character variable i declared
                        // break;
            }
        }
     matrix_display(A[0], row_size1, col_size1);
          }
     if(c == 'B')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[1]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[1][i]=malloc(col_size1*sizeof(int));
           }
    
    
    
    
         for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[1][i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[1], row_size1, col_size1);
     }
      }
     while(flag == 1);
    //return 0;
    }
    
    
    void matrix_display(int *A, int row_size1, int col_size1)
    {
      int i,j;
      printf("The required matrix is\n");
      for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            printf("%d ",A[i][j]);
          printf("\n");
        }
      for(i=0;i<row_size1;i++)
        {
          free(A[i]);
        }
      free(A);
    }

  8. #8
    and the hat of wrongness Salem's Avatar
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    > void matrix_display(int *matrix, int row_count, int column_count);
    Are you paying even the slightest bit of attention?
    In my last post, I said matrix_display was OK, and you go and muck it up again!

    Code:
    $ gcc -Wall bar.c
    bar.c: In function ‘main’:
    bar.c:15:8: warning: unused variable ‘a’ [-Wunused-variable]
    bar.c:12:37: warning: unused variable ‘col_size2’ [-Wunused-variable]
    bar.c:12:27: warning: unused variable ‘row_size2’ [-Wunused-variable]
    bar.c:92:1: warning: control reaches end of non-void function [-Wreturn-type]
    $ 
    $ valgrind ./a.out
    ==6204== Memcheck, a memory error detector
    ==6204== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
    ==6204== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
    ==6204== Command: ./a.out
    ==6204== 
    
    cmd> A
    3 2
    1 2 3
    4 5 6
    The required matrix is
    1 2 
    3 4 
    5 6 
    
    cmd> 
    cmd> ^C==6204== 
    ==6204== HEAP SUMMARY:
    ==6204==     in use at exit: 0 bytes in 0 blocks
    ==6204==   total heap usage: 4 allocs, 4 frees, 48 bytes allocated
    ==6204== 
    ==6204== All heap blocks were freed -- no leaks are possible
    ==6204== 
    ==6204== For counts of detected and suppressed errors, rerun with: -v
    ==6204== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 4 from 4)
    TWO changes.
    1. fix the prototype of matrix_display
    2. remove line A = malloc(2 * sizeof (int **));
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  9. #9
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    So I did what you said I got warnings but... THE program works!
    in total I need 4 variables A B C and D so I added for C and D and once again we're back to square 1
    Code:
    #include<stdio.h>
    #include <stdlib.h>
    
    
    void matrix_display(int *matrix, int row_count, int column_count);
    
    
    
    
    int main (void)
    {
      int row_size1,col_size1,row_size2,col_size2,flag =1;
      int ****A[4];
      int i = 0, j = 0;
      char a,c;
    
    
    
    
    
    
    do
      {
        //  A = malloc(2 * sizeof (int **));
    
    
        printf("\ncmd> ");
        c = getchar();
    
    
        if(c == 'A')
          {
    
    
      scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
      A[0]= malloc(row_size1*sizeof(int*));
      for(i=0;i<row_size1;i++)
        {
          A[0][i]=malloc(col_size1*sizeof(int));
        }
    
    
    
    
    for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            {
              scanf("%d",&A[0][i][j]);
              //      if (A[i][j] == 99) // 'x' is character variable i declared
                        // break;
            }
        }
     matrix_display(A[0], row_size1, col_size1);
          }
     if(c == 'B')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[1]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[1][i]=malloc(col_size1*sizeof(int));
           }
     for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[1][i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[1], row_size1, col_size1);
    
    
    
    
       }
    
    
     if(c == 'C')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[2]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[2][i]=malloc(col_size1*sizeof(int));
           }
    
    
         for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[2][i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[2], row_size1, col_size1);
       }
    
    
     if(c == 'D')
       {
    
    
         scanf("%d %d",&row_size1,&col_size1);
    
    
    
    
         A[3]= malloc(row_size1*sizeof(int*));
         for(i=0;i<row_size1;i++)
           {
             A[3][i]=malloc(col_size1*sizeof(int));
           }
    
    
         for(i=0;i<row_size1;i++)
           {
             for(j=0;j<col_size1;j++)
               {
                 scanf("%d",&A[3][i][j]);
                 //      if (A[i][j] == 99) // 'x' is character variable i declared
                 // break;
               }
           }
         matrix_display(A[3], row_size1, col_size1);
       }
    
    
    
    
      }
     while(flag == 1);
    //return 0;
    }
    
    void matrix_display(int ****A, int row_size1, int col_size1)
    {
      int i,j;
      printf("The required matrix is\n");
      for(i=0;i<row_size1;i++)
        {
          for(j=0;j<col_size1;j++)
            printf("%d ",A[i][j]);
          printf("\n");
        }
      for(i=0;i<row_size1;i++)
        {
          free(A[i]);
        }
      free(A);
    }

  10. #10
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    I made the same changes right?

  11. #11
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    what thing did i miss again?

  12. #12
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    Quote Originally Posted by zafy View Post
    Code:
    void matrix_display(int *matrix, int row_count, int column_count);
    void matrix_display(int ****A, int row_size1, int col_size1)
    The prototype doesn't match the definition, and now you have... how many stars in there?

  13. #13
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    Yes! I got it
    honestly guys thank you so much I appreciate it so much

  14. #14
    TEIAM - problem solved
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    I asked you to do it on the last topic you posted - Can you PLEASE fix your indentation

    This is my preferred style - Indent style - Wikipedia, the free encyclopedia
    AndiPersti likes this.
    Fact - Beethoven wrote his first symphony in C

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    Replies: 3
    Last Post: 06-29-2005, 08:36 AM

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