On Wed, 27 Jan 1999, Matthew Dillon wrote:
> Right now we have a problem with struct sysinit.
>
> The problem is that some SYSINIT functions supply a function taking
> a const void * and a const pointer for data, and other SYSINIT
> functions supply a function taking a void * and a non-const pointer
> for data.
>
> What this means, effectively, is that we want one of two SYSINIT
> structures where both the function argument and udata are of the
> same type. Something like the union shown below. If the function
> argument type does not match the data type we want the initialization
> to generate a warning.
>
> struct sysinit {
> unsigned int subsystem; /* subsystem identifier*/
> unsigned int order; /* init order within
> subsystem*/
> union {
> struct {
> void (*func) __P((void *));
> void *udata; /* multiplexer/argument */
> } n;
> struct {
> void (*func) __P((const void *));
> const void *udata; /* multiplexer/argument */
> } c;
> } u;
> si_elem_t type; /* sysinit_elem_type*/
> };
>
> Unfortunately, GCC isn't smart enough to match the function type
> to the correct structure - it always stuffs it into the first structure.
Overloading a struct? Yuck :(
>
> So the above cool hack will not work :-(.
Overloading is just a bad hack in concept.
>
> I can't think of how to do this without actually having two different
> sysinit structures - on that uses a non-const function and data element,
> and one that uses a const function and data element. While having two
> sysinit structures would work, it would be a little iffy keeping them
> in sync with each other so the kernel init call code doesn't have to deal
> with both types.
>
> struct c_sysinit {
> unsigned int subsystem; /* subsystem identifier*/
> unsigned int order; /* init order within
> subsystem*/
> void (*func) __P((void *));
> void *udata; /* multiplexer/argument */
> si_elem_t type; /* sysinit_elem_type*/
> };
>
> struct n_sysinit {
> unsigned int subsystem; /* subsystem identifier*/
> unsigned int order; /* init order within
> subsystem*/
> void (*func) __P((const void *));
> const void *udata; /* multiplexer/argument */
> si_elem_t type; /* sysinit_elem_type*/
> };
>
> The SYSINIT problem accounts for about half the remaining compilation
> warnings. I would like to find a good solution for it.
>
> -Matt
> Matthew Dillon
> <dil...@backplane.com>
>
>
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