On 07/18/2012 07:31 AM, Andrew Haley wrote:
On 07/18/2012 03:00 PM, ap wrote:
I have the following #define in my code
#define SWAP64(p) ( (*(unsigned _int64*)(p)) = _byteswap_uint64(*(unsigned _int64*)(p)))
When I compile I get the error: expected primary-expression before 'unsigned',
when I use SWAP64
Does anybody have any idea?
Yes. This is not legal C code: a cast expression is not an lvalue.
Do this:
#define SWAP64(P) \
unsigned _int64 *tmp = (unsigned _int64 *)P; \
*tmp = _byteswap_uint64(*tmp);
But be aware that you might have aliasing errors, so this code may
still not be legal. I suspect you have some very old C code.
You are also likely to step on any variable named "tmp".
It would be better to re-write _byteswap_uint64() as a macro or
as a function taking two void pointers and do the cast within
the function.
--
Michael Eager eager@xxxxxxxxxxxx
1960 Park Blvd., Palo Alto, CA 94306 650-325-8077
