Strcpy/memory allocation problem

[ImNotaBot]

  char str[]="Hello";                 // 5 chars
  char *tmpstr;
  int size = strlen(str);              // 5
  tmpstr = new char[size+1];   // char[6]
  strcpy_s(tmpstr, size, str);         <error
  tmpstr[size]=0;

results in . But i have no clue why. Why do i get this error?

[Paul McKenzie]

Why do i get this error?

tmpstr = new char[size+1];   // char[6]
strcpy_s(tmpstr, size, str);         <error

http://msdn.microsoft.com/en-us/libr...7;28v=vs.90%29

The strcpy_s function copies the contents in the address of strSource, including the terminating null character, to the location specified by strDestination.

Regards,

Paul McKenzie

[ImNotaBot]

Okay thankyou for the fast reply. But for what reason do I have to state the size of the source string? (2nd parameter)

Greets

[ovidiucucu]

Have a look in MSDN Library, at Security Enhancements in the CRT.

[ImNotaBot]

Ahh untill now i thought, that the new secure functions work in a different way. In case if strcpy_s i thought just <size> characters would be copied. Well, I see no gain in there, hence i wont use them anymore... i guess strncpy is my friend.

Thanks a lot for the enlightment :-D

[VladimirF]

i guess strncpy is my friend

If you are looking for a friend, check out strncpy_s
But to make a copy of a string, use strdup()

[ImNotaBot]

Great suggestion. Thanks!

[ovidiucucu]

Ahh untill now i thought, that the new secure functions work in a different way. In case if strcpy_s i thought just <size> characters would be copied. Well, I see no gain in there, hence i wont use them anymore... i guess strncpy is my friend.

That makes sense to avoid buffer overrun in case you pass a larger source or some non nul-terminated garbage.
If a "_s function" didn't pass the run-time tests, it shows you that something is wrong with your program, while "your friend" strncpy doesn't.

See also these articles:

• Microsoft Visual Studio: Secure CRT Functions
• Michael Howard - Saying Goodbye to an Old Friend

[ Later edit ]
And of course, as Vlad already stated, strncpy_s may be an even better friend...