urgent - pointers to pointers

Hello
I coded this: (in Borland 5.02)
run it! it create 2d array and free allocated memories.
regards

#include <windows.h>
#include <stdio.h>
int main()
{
int i;
char **str;
//allocate 2d array in heap
*str = calloc(5,sizeof(char*));
for(i=0;i<5;i++)
{
str[i] = (char*)(calloc(10,sizeof(char)));
strcpy(str[i],"test text\n");
printf("%s",str[i]);
}
//free heap
for(i=0;i<5;i++)
free(str[i]);
free(str);
system("pause");
}

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>> *str = calloc(5,sizeof(char*));

You shouldn't dereference an uninitialized pointer.


>> strcpy(str[i],"test text\n");

You only allocated space for 10 characters. That's not enough for the terminating '\0'.

>>char **str;

>>i dont know what is it.

Concentrating on this bit of your question ... maybe this would help [added as points.txt - so rename it]?

#include<stdio.h>

int main(void)
{
    char c = 'z';
   
    char * cp = &c;
   
    char ** cpp = &cp;

    puts("\tConsider the following\n");

    puts("char    c   = 'z';");
    puts("char *  cp  = &c;");
    puts("char ** cpp = &cp;");

    /* outputs z z z */
   
    puts("\nprintf(\"%c %c %c\", c, *cp, **cpp);");
    printf("\n%c %c %c\n\n", c, *cp, **cpp);
   
    printf("c is located in memory at: %p\n\n", &c);
   
    printf("cp is pointing to c, and that means it contains the same value: %p\n\n", cp);
   
    printf("cp is itself located at memory address: %p\n\n", &cp);
   
    printf("and, as cpp is pointing to cp, it contains that same address: %p\n\n", cpp);
   
    printf("so, if we dereference, cpp we'll get: %p\n\n", *cpp);
   
    printf("and, if we dereference that, we'll get c itself again: %c\n\n", **cpp);
   
    return 0;
}





points.txt

trying oout now..thanks

would it matter if the string literal is stored in the token...

while(fgets(maxline,80,fp)!=NULL)
{
maxline[strlen(maxline)]='\0';
token = strtok(line, limit);
while(token!=NULL)
{
str=token;

token=strtok(NULL,limit);
}

table[i]=token;

...
,...

while(fgets(maxline,80,fp)!=NULL)
{
maxline[strlen(maxline)]='\0';             // <--- this is unnecessary. fgets already adds the '\0'
token = strtok(line, limit);               // <--- didn't you mean to use maxline instead of line ?
while(token!=NULL)
{
str=token;                                 // <--- you're not using str ...
 
token=strtok(NULL,limit);
}
 
table[i]=token;                            // <--- token is NULL here. Is that what you want ?

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sorry, this is the one..i was typing too fast...


while(fgets(line,80,fp)!=NULL)
      {  
            token = strtok(line, delimiter);
            count=0;
            
            while(token != NULL)
            {      
                  count++;
                  
                  if(count == 2)
                        str = token;
      
                  token = strtok(NULL, delimiter);
            }
            
       table[i] =calloc(strlen(str)+1,sizeof(char));
            
            strcpy(table[i],str);
            
            i++;
      }

i  think, i do understand now...

since the str would be holding the value of token, when i change the token and pass it to str to keep the value, it would be holding the latest value...so, the pointer would be pointing to th elatest value...