Re: [RFC][PATCH] compat_uint64_t type

[Patrick McHardy <kaber@trash.net>]

Andreas Schwab wrote:
> Patrick McHardy <kaber@trash.net> writes:
> 
>>I'm not sure if we should really introduce this new type, it is
>>misleading for at least x86. IIRC the situation there is:
>>
>>- gcc < 4.0 always aligns u64 types to 4byte
> 
> 
> Are you sure about that? I can't reproduce that with gcc 3.3.3.

I mixed up the versions, the change was between 2.x and 3.x:

gcc-2.95 -O2:
basic type:     align 4
embedded type:  align 4
gcc-3.3 -O2:
basic type:     align 8
embedded type:  align 4

It only shows with optimization, with -O0 gcc-2.95 also uses 8 for
the basic type.

>>So there is no one compat_uint64_t type, but it depends on the
>>situation.
> 
> 
> The alignment of standalone objects is uninteresting, what is important is
> getting compatible layout of aggregates.

I couldn't come up with a realistic example where people would make
mistakes because of this, so I guess I have to agree, although my
feeling still disagrees :)