[LLVMdev] Incorrect loop optimization when building the Linux kernel

[David Majnemer]

On Monday, December 8, 2014, Joerg Sonnenberger <joerg at britannica.bec.de>
wrote:

> On Mon, Dec 08, 2014 at 02:03:28AM -0800, David Majnemer wrote:
> > Nick, consider:
> >
> > char a[0];
> > char b[0];
> >
> > at run-time:
> > (gdb) p &a
> > $1 = (char (*)[]) 0x60103c
> > (gdb) p &b
> > $2 = (char (*)[]) 0x60103c
> >
> > Even if this is not safe at the C or C++ level, this comparison could
> > return equal or not equal depending on what the linker chooses to do.
>
> It is invalid C as is the original code. If you want to play such linker
> games, mark one of the objects involved as weak.


Right, but nothing forbids this comparison at the IR level.


>
> Joerg
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