Checking for string contents? string Length Vs Empty String

Question

Which is more efficient for the compiler and the best practice for checking whether a string is blank?

1. Checking whether the length of the string == 0

Answer 1

In languages that use C-style (null-terminated) strings, comparing to "" will be faster

Actually, it may be better to check if the first char in the string is '\0':

char *mystring;
/* do something with the string */
if ((mystring != NULL) && (mystring[0] == '\0')) {
    /* the string is empty */
}

In Perl there's a third option, that the string is undefined. This is a bit different from a NULL pointer in C, if only because you don't get a segmentation fault for accessing an undefined string.