[cfe-dev] [llvm-dev] [3.8 Release] Please write release notes!

John McCall via cfe-dev cfe-dev at lists.llvm.org
Fri Mar 4 14:47:42 PST 2016

> On Mar 3, 2016, at 6:05 AM, Joerg Sonnenberger via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> On Wed, Mar 02, 2016 at 11:34:27PM -0800, John McCall via llvm-dev wrote:
>> When that’s not practical, you can instead reduce the alignment requirements
>> of the pointer.  If the pointer is to a struct that represents that layout of a
>> serialized structure, consider making that struct packed; this will remove any
>> implicit internal padding that the compiler might add to the struct and
>> reduce its alignment requirement to 1.
>>  struct file_header {
>>    uint16_t magic_number;
>>    uint16_t format_version;
>>    uint16_t num_entries;
>>  } __attribute__((packed));
> If we want to include this example, it is likely a good idea to point
> out that packed and aligned can be combined, i.e. if you know that the
> file_header copies are going to be at an aligned location, adding the
> attribute results in significantly better code on platforms like ARM
> with strict alignment.

I’d like to keep the release note relatively focused on our recommended ways
to fix alignment bugs.


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