Difference between 'strcpy' and 'strcpy_s'?

Question

When i tries to use strcpy to copy a string it gave me a compile error.

error C4996 \'strcpy\': This function or variable may be unsafe.
         


        

Answer 1

strcpy is a unsafe funtion. When you try to copy a string using strcpy(), to a buffer which is not large enough to contain it, it will cause a buffer overflow.

strcpy_s() is a security enhanced version of strcpy(). With strcpy_s you can specify the size of the destination buffer to avoid buffer overflows during copies.

char tuna[5];  // a buffer which holds 5 chars incluing the null character.
char salmon[] = "A string which is longer than 5 chars";

strcpy( tuna, salmon ); // This will corrupt your memory because of the buffer overflow.

strcpy_s( tuna, 5, salmon ); // strcpy_s will not write more than 5 chars.