Date: Tue, 28 May 2002 20:43:50 -0700 From: "J. Mallett" <jmallett@FreeBSD.org> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: standards@FreeBSD.ORG Subject: Re: Q&D implementation of dlfunc() Message-ID: <20020528204350.B74072@FreeBSD.ORG> In-Reply-To: <200205290340.g4T3erxr010138@khavrinen.lcs.mit.edu>; from wollman@khavrinen.lcs.mit.edu on Tue, May 28, 2002 at 11:40:53PM -0400 References: <20020528195236.A66528@FreeBSD.ORG> <200205290340.g4T3erxr010138@khavrinen.lcs.mit.edu>
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* From Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
> <<On Tue, 28 May 2002 19:52:36 -0700, "J. Mallett" <jmallett@FreeBSD.ORG> said:
>
> > rv = (uintptr_t)dlsym(handle, symbol);
>
> For the same reason as you can't cast from a data pointer to a
> function pointer, there's no guarantee that you can cast from a
> uintptr_t (if such a type even exists) to a function pointer. Since
> we're depending on all pointers having the same representation, I'd
> rather make it explicit.
Right, I understand the situation, and how evil it is. Look at the code
I put below, I think I forgot to include parts of my hello world, which
removes that assumption, by doing (note inocrrectness of hello was to deal
with having prototypes in scope, I could have done something cleaner, but...):
convptr hello(convptr function, uintptr_t *data)
{
printf("## hello: %p, %p\n", function, data);
printf("Hello, world!\n");
return function;
}
int main(int argc, char *argv[])
{
convptr foo, bar;
uintptr_t data[sizeof(convptr)/sizeof(uintptr_t)];
printf("## main: 0x%x, %p\n", argc, argv);
function_to_data_ptr((convptr)data_to_function_ptr, data);
data_to_function_ptr(&foo, data);
function_to_data_ptr((convptr)hello, data);
(*foo)(&bar, data);
(*bar)(NULL, NULL);
return 0;
}
--
J. Mallett <jmallett@FreeBSD.org> FreeBSD: The Power To Serve
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