On 2007-07-26 15:43:07 +0200, Michael Kerrisk wrote: > By the way, note the following in the spec of <stddef.h>: > > 11296 CX NULL Null pointer constant. The macro shall expand to an integer > constant expression + > 11297 with the value 0 cast to type void *.
Yes, "The macro shall expand to an integer constant expression with the value 0 cast to type void *" was not in Issue 6. Now, note that the type of a null pointer is not necessarily void *, and a null pointer is not necessarily constant! So, if you say NULL instead of "null pointer", the behavior remains unspecified if the pointer is null and not constant. Remember that the C standard allows to implement functions of the standard library as macros, so that an implementation may be able to do the difference between a constant value and a non-constant value, something in this style: #define mpfr_cmp_ui(_f,_u) \ (__builtin_constant_p (_u) && (_u) == 0 ? \ mpfr_sgn (_f) : \ mpfr_cmp_ui_2exp ((_f),(_u),0)) (this is taken from the MPFR source code, but this is just to show you the possible implications). -- Vincent Lefèvre <[EMAIL PROTECTED]> - Web: <http://www.vinc17.org/> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/> Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)
