Andrew Haley <aph@xxxxxxxxxx> writes:
> Matthew Woehlke writes:
> > I have a code snippet that looks roughly like this:
> >
> > extern void my_free(void* ptr);
> >
> > int foo()
> > {
> > volatile long * bar;
> > ...
> > my_free(bar);
> > }
> >
> > This generates the warning 'cast discards qualifiers from pointer target
> > type' at my_free() (gcc 3.4.3). Other than disabling the flag that
> > generates the warning (in general I want these warnings!), how do I
> > suppress this? my_free is of course a free() wrapper, i.e. I don't see
> > any problems discarding the qualifier at this point. I already tried
> > this, which seems like it used to work (I am moving the code from one
> > project to another):
> >
> > my_free(void*)bar);
> >
> > ...and it doesn't help.
>
> I think this is bad practice. You'd be far better advised to malloc()
> the memory, keep a void* pointer to it, but cast to volatile long *
> when volatile is actually required.
Note that this is also somewhat dubious on a strict reading of the C
standard. The standard discusss access to volatile qualified objects,
and it says that casting away volatile is undefined. The standard
says absolutely nothing about volatile qualified pointers to
non-volatile objects. So you should not expect any particular
semantics from a volatile-qualified pointer which points to a
non-volatile-qualified object.
Ian
