This is the mail archive of the
gcc-help@gcc.gnu.org
mailing list for the GCC project.
Re: Where does C standard mention alignment requirements as written in gcc manual?
- From: john smith <wempwer at gmail dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: gcc-help at gcc dot gnu dot org
- Date: Tue, 18 Aug 2015 17:57:36 +0200
- Subject: Re: Where does C standard mention alignment requirements as written in gcc manual?
- Authentication-results: sourceware.org; auth=none
- References: <CAKmQUfai7NdLwiQRQ-0Nd4biPjyBgMp46K3WhO7xOn=Oi4zLLw at mail dot gmail dot com> <20150818155042 dot GC30482 at gate dot crashing dot org>
On Tue, Aug 18, 2015 at 5:50 PM, Segher Boessenkool
<segher@kernel.crashing.org> wrote:
> On Tue, Aug 18, 2015 at 05:04:28PM +0200, john smith wrote:
>> In gcc manual it says:
>>
>> "Note that the alignment of any given struct or union type is required
>> by the ISO C standard to be at least a perfect multiple of the lowest
>> common multiple of the alignments of all of the members of the struct
>> or union in question."
>>
>> Where exactly is this requirement mentioned in C standard? I was
>> looking for it in both C99 and C11 drafts and couldn't find it.
>
> C99 6.7.2.1/12 ?
It just says that "Each non-bit-field member of a structure or union
object is aligned in an implementation-defined manner appropriate to
its type.". It doesn't require an overall alignment of the structure
to be "at least a perfect multiple of the lowest common multiple of
the alignments of all of the members of the struct".
--
<wempwer@gmail.com>