Access vs. Address ?

Access vs. Address ?

[W. Wesley Groleau (Wes)]

> It is surprising how MUCH Ada code out there relies on the assumption
> that all pointers are the same size as addresses. ...

This assumption is normally accompanied by a more dangerous assumption
that all pointers ARE addresses.  Even though this is usually true,
it IS NOT REQUIRED by either LRM.  And even when it is true, what is
happening is usually NOT what the programmer meant.  I refer to the
Unchecked_Conversion of an access value to an address when what is
wanted is the address of the accessed item.

begin -- Soapbox

   -- The address of  Pointer.all  is  Pointer.all'Address --

   -- it is NOT  Convert_To_Address (Pointer);

   -- The latter works SOMETIMES with SOME compilers.  And when it doesn't
   -- work, it can REALLY screw things up!

end Soapbox;

Feel free to share this with your beginning programmers  :-)

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W. Wesley Groleau (Wes)                                Office: 219-429-4923
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Re: Access vs. Address ?

[Robert Dewar]

Wes says

"   -- The address of  Pointer.all  is  Pointer.all'Address --"

and advises against use of unchecked_conversoin of pointers <-> addresses.

True enough. Even better advice in Ada 95 is always to use the
Address_To_Acces_Conversions package. Note that even with this
package, the conversion of an address to a pointer to unconstrained
array is VERY dubious (where do the bounds come from?)