Re: [Qemu-devel] CMSG_SPACE() causing compile time error on Mac OS X

[Programmingkid <programmingkidx@gmail.com>]

On Jan 18, 2016, at 12:45 PM, Eric Blake wrote:

> On 01/17/2016 04:45 PM, Programmingkid wrote:
>>> What's the definition of the CMSG_SPACE macro under OS X?
>>> 
>>> Paolo
>> 
>> #define	CMSG_SPACE(l)		(__DARWIN_ALIGN32(sizeof(struct cmsghdr)) + __DARWIN_ALIGN32(l))
> 
> And the definition of __DARWIN_ALIGN32()?
> 
> It looks like the definition is not properly resulting in a compile-time
> constant, and therefore the warning about the initializer is resulting
> because you can't initialize a dynamically-sized array.  But you still
> haven't shown us why the headers are resulting in a non-constant size.

I tried what Peter Maydell did and here are the results:

typedef __darwin_size_t size_t;

char control[(((__darwin_size_t)((char *)(__darwin_size_t)(sizeof(struct cmsghdr)) + (sizeof(__uint32_t) - 1)) &~ (sizeof(__uint32_t) - 1)) + ((__darwin_size_t)((char *)(__darwin_size_t)(sizeof(int) * 16) + (sizeof(__uint32_t) - 1)) &~ (sizeof(__uint32_t) - 1)))] = { 0 };

It looks like the problem was actually with this part: = { 0 };