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

For C strings,

if (s[0] == 0)

will be faster than either

if (strlen(s) == 0)

or

if (strcmp(s, "") == 0)

because you will avoid the overhead of a function call.