>On 12/9/98 at 5:48 PM, tod.blanchard at kanisa.com (Blanchard, Tod) wrote:
>
>> In practice most C compilers are lax about checking for this and don't
>> produce more than a single read/write data segment.  For instance, I just
>> tried that program on Solaris using gcc and it worked exactly as I expected.
>> Not even a warning. Most good C++ compilers generate a warning at
>> initialization warning that a non-const pointer was initialized pointing to
>Hmmmm.....makes me think this is a generic problem with operating system 
>design in addition to a language problem.

This goes all the way back to some of the original FORTRAN 
implementations.  In FORTRAN (up through FORTRAN-IV and FORTRAN-77, 
anyway), everything is call-by-reference, and most implementations used a 
"constant pool" for literals.  The classic mistake would be to pass a 
"constant" to a subroutine which ended up modifying that constant -- 
future uses would then be corrupted:

       CALL X(1)
       I = 1 + 1
       WRITE (6, 10) I
    10 FORMAT (1H1, 7H1 + 1 =, I2)
       STOP
       END
       SUBROUTINE X(I)
       I = 2
       RETURN
       END


See <http://catless.ncl.ac.uk/Risks/16.38.html#subj9> for more discussion 
on this.



     -- tim