Thread: Simple Question on Correct Usage of memset

Using sizeof as the size argument will only work for arrays. For dynamically allocated memory you need to give the same size argument as you gave to new:

Code:

char *p;
...
p = new char[strlen ( SOME_STRING ) + 1];
memset ( p, 0, strlen ( SOME_STRING ) + 1 );

Your current code only takes the sizeof a pointer, which would be something small like 4.

>Should one memset the additional element used for the null or not?
It depends on the value you set the other elements to. If it's 0 then it couldn't hurt. If it's not 0 then there's no real point because you'll have to set it to 0 separately. However, memset for strings isn't really needed as you can allocate the memory and make the string empty by setting the first character to '\0':

Code:

char *p;
...
p = new char[strlen ( SOME_STRING ) + 1];
*p = '\0;

The effect is the same as long as you treat p as the start of the string when you begin to work with it.