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In article <4elq8a$j0b@taurus.fccc.edu> slifker@castor.fccc.edu
(Michael J. Slifker) writes: 
<snip>
   Question 1:

   According to K&R II, "pointer comparison is defined only for parts
   of the same object". In particular, this is stated to apply to 
   equality operators (== and !=). Harbison & Steele (_C: A Reference
   Manual_) agree with this in the case of relational operators, but
   state that pointer equality is defined provided both operands are
   pointers to compatible types. The latter makes much more sense to
   me, but can anyone tell me what the Standard has to say? 

Equality and inequality are defined for any two valid pointers of the
same type, or if one is a pointer to void and the other is a pointer
to an object or incomplete type.

<snip>
   Question 2:

   I've compiled the following program with gcc:

   -----------

   #include <stdio.h>

   char *str1 = "Hello, World\n";
   const char *str2 = "Hello, World\n";

   int main(void)
   {
     str1[0] = 'J';
     printf("%s", str2);
     return 0;
   }

   -----------

   ...and it prints out "Jello, World". This seems odd, at least to
   me. Is this a bug, or is the behavior above officially undefined?

Attempt to modify a string literal results in undefined behaviout. Any
behaviour by the implementation is then valid.

Cheers
Tanmoy
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