pointer checking

[Danny]

In article <228 at gandalf.littlei.UUCP> martin at littlei.UUCP (martin) writes:
~...
~sizeof(ptr) != sizeof(int).  I know that C does not gripe if

    Yes, indeed, it is wrong to assume that sizeof (ptr) == sizeof (int),
BUT: read on!

~Example:
~
~char *ptr;
~
~if (ptr) {		/* WRONG !!!!!! */
~    do something
~}

    Would you expect a C compiler to generate erroneous code for the
following?

    char   a;
    int    b;
    long   c;
    double d;
    
    if (a) {
      ...
    if (b) {
      ...
    if (c) {
      ...
    if (d) {
      ...
    
    The compiler knows exactly what size each of the above types is.
Pointers, as far as comparison goes, are exactly the same.

Any compiler that doesn't properly compile
    char *p;
    
    if (p) {
        do something;
    }
is broken.  The compiler knows the size of the pointer, and _should_
compare against the same size of a constant zero.

                                            Danny
-- 
				Daniel S. Cox
				(seismo!gatech!itm!danny)