Re: const correctness

Tom Lane <tgl@sss.pgh.pa.us> wrote:
 
> In general I don't have an objection to adding "const" to
> individual routines, so long as it doesn't create propagating
> requirements to const-ify other code.  This may be the only way to
> do it.
 
As I understand it (although I'm no C expert), a "const" qualifier
on a function parameter declaration is a promise that the function
will not modify what is thus qualified.  That means that it can't
pass a const parameter to another function as a parameter not also
declared const.  It doesn't say anything about the object itself or
what is returned from the function.
 
So a non-const parameter in can be passed to a const parameter in a
call, but not vice versa.  And a variable need not be declared const
to pass it to a function as a const parameter.  I don't know if this
meets your conditions for non-propagation.
 
-Kevin