Proper way to empty a C-String

It depends on what you mean by “empty”. If you just want a zero-length string, then your example will work.

This will also work:

buffer[0] = '\0';

If you want to zero the entire contents of the string, you can do it this way:

memset(buffer,0,strlen(buffer));

but this will only work for zeroing up to the first NULL character.

If the string is a static array, you can use:

memset(buffer,0,sizeof(buffer));