Re: [UPDATED PATCH] fix memory corruption from misinterpreted bad_inode_ops return values

[Al Viro <viro@ftp.linux.org.uk>]

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.