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SubjectRe: [UPDATED PATCH] fix memory corruption from misinterpreted bad_inode_ops return values
On Thu, Jan 04, 2007 at 03:21:06PM -0800, Mitchell Blank Jr wrote:
> Linus Torvalds wrote:
> > Well, that probably would work, but it's also true that returning a 64-bit
> > value on a 32-bit platform really _does_ depend on more than the size.
>
> Yeah, obviously this is restricted to the signed-integer case. My point
> was just that you could have the compiler figure out which variant to pick
> for loff_t automatically.
>
> > "let's not play tricks with function types at all".
>
> I think I agree. The real (but harder) fix for the wasted space issue
> would be to get the toolchain to automatically combine functions that
> end up compiling into identical assembly.

Can't do.

int f(void)
{
return 0;
}
int g(void)
{
return 0;
}
int is_f(int (*p)(void))
{
return p == f;
}
main()
{
printf("%d %d\n", is_f(f), is_f(g));
}
would better produce
1 0
for anything resembling a sane C compiler. Comparing pointers to
functions for equality is a well-defined operation and it's not
to be messed with.

You _can_ compile g into jump to f, but that's it. And that, AFAICS,
is what gcc does.
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