Setting a string to null in C

Is setting 开发者_StackOverflow中文版a string to '\0' the same thing as setting a string to NULL in other languages? Or... does setting a string to '\0' mean that the string is simply just empty?

char* str = '\0'

I have different functions to use for null strings and empty strings, so I don't want to accidentally call one of my empty string functions on a null string.

Your line char *str = '\0'; actually DOES set str to (the equivalent of) NULL. This is because '\0' in C is an integer with value 0, which is a valid null pointer constant. It's extremely obfuscated though :-)

Making str (a pointer to) an empty string is done with str = ""; (or with str = "\0";, which will make str point to an array of two zero bytes).

Note: do not confuse your declaration with the statement in line 3 here

char *str;
/* ... allocate storage for str here ... */
*str = '\0'; /* Same as *str = 0; */

which does something entirely different: it sets the first character of the string that str points to to a zero byte, effectively making str point to the empty string.

Terminology nitpick: strings can't be set to NULL; a C string is an array of characters that has a NUL character somewhere. Without a NUL character, it's just an array of characters and must not be passed to functions expecting (pointers to) strings. Pointers, however, are the only objects in C that can be NULL. And don't confuse the NULL macro with the NUL character :-)

No, in this case you're pointing to a real (non-null) string with a length of 0. You can simply do the following to set it to actual null:

char* str = NULL;