On 2/22/21 10:37 AM, Michael J. Baars wrote:
On Mon, 2021-02-22 at 01:29 -0800, Andrew Pinski wrote:
On Mon, Feb 22, 2021 at 1:17 AM Michael J. Baars
<mjbaars1977....@cyberfiber.eu> wrote:
Hi,
I just wrote this little program to demonstrate a possible flaw in both malloc
and calloc.
If I allocate a the simplest memory region from main(), one out of three
optimization flags fail.
If I allocate the same region from a function, three out of three optimization
flags fail.
Does someone know if this really is a flaw, and if so, is it a gcc or a kernel
flaw?
There is no flaw. GCC (kernel, glibc) all assume unaligned accesses
on x86 will not cause an exception.
Is this just an assumption or more like a fact? I agree with you that byte
aligned is more or less the same as unaligned.
IIRC it's a fact, unless you change EFLAGS to enable the unaligned
access exception flag, which is forbidden by the ABI.
Thanks,
Andrew
Regards,
Mischa.
