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Dec 2nd, 2008
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Re: Help, Im trying to implement my own strcpy

Click to Expand / Collapse  Quote originally posted by StuXYZ ...
can I just add, you need to remember to add a
*dest=0; line after the while. You will need something similar in any of the other posts.
No with Arkm's algorithm you don't because it will also copy the null terminator.
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Re: Help, Im trying to implement my own strcpy

Regrettably, it's not ArkM's algorithm. It's K&R code.
Thank you, Ancient Dragon: this code is OK, it copies null byte
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Re: Help, Im trying to implement my own strcpy

What about Buffer Overflow?
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Re: Help, Im trying to implement my own strcpy

Click to Expand / Collapse  Quote originally posted by Laiq Ahmed ...
What about Buffer Overflow?
Look at the requirements: if you forgot strcpy specification I can recall, try to search the target size there
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Re: Help, Im trying to implement my own strcpy

Click to Expand / Collapse  Quote originally posted by Laiq Ahmed ...
What about Buffer Overflow?
That is a problem with all standard C functions. If you use one of the new Microsoft compilers, Microsoft declared them depreciated and wants us to use the _s functions, such as strcpy_s(), which has an additional destination buffer size parameter. But even that could cause buffer overflow if the calling function passed the wrong buffer size. There is no 100% bullet-proof method in C to prevent buffer overflow. But if you follow the rules and bother to actually read the function's requirements then you can minimize the buffer overflow problem.
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wow this thing is rolling!!

I modified the program it looks like this but no doubt theres something wrong as it wont output anything I await your wisdom guys

C++ Syntax (Toggle Plain Text)
  1. #include <iostream>
  2. #include <cstring>
  3. using std::cin;
  4. using std::cout;
  5.  
  6. void StrCpy(char * Dest , char* Src )
  7. {
  8.  int i;
  9.  char *tmp = new char[strlen(Src)+1];
  10.  for(i = 0 ; *Src!='\0' ; Src++)
  11.     tmp[i]=*Src;
  12.  tmp[i]='\0'; 
  13.  Dest = tmp; 
  14.  for(int i= 0 ; tmp[i]!='\0' ; i++)
  15.    cout << tmp[i];
  16. }
  17.  
  18. void main()
  19. {  
  20.  
  21. char *string1;
  22. char * string2 = "EL";
  23.  
  24.  
  25. StrCpy(string1, string2);
  26.  // while(*string1)
  27.  //   cout << *string1++; 
  28. }
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Re: Help, Im trying to implement my own strcpy

Your version doesn't work because the first parameter Dest needs to be passed by pointer, not by value
C++ Syntax (Toggle Plain Text)
  1. #include <iostream>
  2. #include <cstring>
  3. using std::cin;
  4. using std::cout;
  5.  
  6. void StrCpy(char ** Dest , char* Src )
  7. {
  8.  int i;
  9.  char *tmp = new char[strlen(Src)+1];
  10.  for(i = 0 ; *Src!='\0' ; Src++)
  11.     tmp[i]=*Src;
  12.  tmp[i]='\0'; 
  13.  *Dest = tmp; 
  14.  for(int i= 0 ; tmp[i]!='\0' ; i++)
  15.    cout << tmp[i];
  16. }
  17.  
  18. void main()
  19. {  
  20.  
  21. char *string1 = 0;
  22. char * string2 = "EL";
  23.  
  24.  
  25. StrCpy( &string1, string2);
  26.  // while(*string1)
  27.  //   cout << *string1++; 
  28. }
Last edited by Ancient Dragon; Dec 2nd, 2008 at 10:55 pm.
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Re: Help, Im trying to implement my own strcpy

C++ Syntax (Toggle Plain Text)
  1. for(i = 0 ; *Src!='\0' ; Src++)
  2.     tmp[i]=*Src;

should increment 'i' also. as of now 'i' remains 0 throughout.
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Dec 3rd, 2008
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Re: Help, Im trying to implement my own strcpy

It worked wonders, just a lil bit confused why the extra pointer indirection was needed but I think that'll come in the future
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This thread is solved

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