[PATCH] Define libc_max_align_t

[pinskia@gmail.com]

> On Apr 2, 2015, at 8:40 AM, Rich Felker <dalias@libc.org> wrote:
> 
>> On Thu, Apr 02, 2015 at 12:01:34AM +0200, Andreas Schwab wrote:
>> Florian Weimer <fweimer@redhat.com> writes:
>> 
>>> +/* This mirrors the C11 max_align_t type provided by GCC, but it is
>>> +   also available in C99 mode.  */
>>> +typedef struct {
>>> +  long long ll __attribute__ ((__aligned__ (__alignof__ (long long))));
>>> +  long double ld __attribute__ ((__aligned__ (__alignof__ (long double))));
>>> +} libc_max_align_t;
>> 
>> Why aren't the attributes no-ops?
> 
> Because gcc is insane.

No. Just some abi's are insane. 

> 
> On gcc, __alignof__ returns the "preferred alignment for optimization"
> that gcc would use allocating such objects individually, not the "ABI
> alignment" that would be used in structs, etc.

Except some abis talk about different alignment for where the field is located. 

> 
> Rich