Re: [Xen-devel] mini-os: x86_64: crash passing double arguments

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.07.14 at 14:54, <Ian.Campbell@xxxxxxxxxx> wrote:
> On Wed, 2014-07-02 at 13:44 +0100, Jan Beulich wrote:
>> >>> On 02.07.14 at 14:37, <Ian.Campbell@xxxxxxxxxx> wrote:
>> > I was assuming that 16-bytes (-mpreferred-stack-boundary=4) was the
>> > implied default by the architecture's ABI, hence the compiler would
>> > already naturally deal with things requiring 32 or 64 byte alignment
>> > (with a starting assumption of 16-byte alignment on function entry).
>> 
>> That is the default in the absence of any other options. Someone
>> adding -mavx or some such to their compiler options would, however,
>> break this. One might argue that (s)he should then also add the
>> other option, but we can as well be on the safe side from the
>> beginning.
> 
> OK.
> 
> I wonder how e.g. pthreads handles this? Is there some gcc provided
> #define which exposes the result of all these options so pthreads can
> DTRT with the stacks?

I have no idea, but would kind of expect user land stacks to start at
page (or at least cache line) boundaries anyway.

Jan


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