Re: Memory overwrite?

[dewar@cs.nyu.edu (Robert Dewar)]

T.E.D. says that all four Ada compilers he has used generate warnings if
uninitialized variables are passed as in parameters.

Just so that no one gets confused, it is *impossible* to generate such
warnings in all cases (to do so would require:

   (a) telepathy on the part of the compiler to guess the input in advance
   (b) a solution to the halting problem

otherwise, no sweat :-)

Of course warnings can be generated in some simple cases. But it is not the
case that worrying about the semantic effects of uninitialized variables
is unimportant because warnings can be generated.

Some obvious examples where the compiler cannot check is for the case of
array elements, references to dynamically allocated values (x.all), and
global variables where the compiler cannot tell who might have initialized
them.

So T.E.D. is I am afraid operating from a sense of false security (it is
in fact one disadvantage of the generation of such error messages, it
sometimes lulls people into this sense of false security). It is true
that the warnings are very useful, but don't depend on them!