Ian Lance Taylor writes:
> 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.
Mmmm, but let's say you want a dynamic shared buffer between threads.
How else would you do it, other than a malloc() and a cast?
Andrew.
