nul!null.txt

C语言库函数的源代码,是C语言学习参考的好文档。

+++Date last modified: 05-Jul-1997

Q: My compiler gives me a warning whenever I try to assign or compare the
   value of NULL to an integral type (char, short, int, long). What's the
   matter?


A: According to the standard, NULL is a macro defined as a null pointer
   constant so you should expect warnings (at least!) when trying to assign a
   pointer to an integral type without a (highly questionable) cast!

   This is a fairly common error since people hear other programmers talking
   all the time about "a null character". As it turns out, ASCII shorthand
   notation for '\0' happens to be NUL, hence the confusion. In SNIPPETS, I
   explicitly work around this common error (in SNIPTYPE.H) with the line...

   #define NUL '\0'

   The moral of this story is to know the difference between ASCII NUL and C
   NULL, and use whichever is correct for your application. In many cases,
   the correct "null" may be NUL, not NULL.

   Is this confusing enough? ;-)