On Friday 02 January 2009 17:20:47 Wolfgang Denk wrote:
In message vapier@gentoo.org you wrote:
From: Bryan Wu bryan.wu@analog.com
A couple of buffers in the fat code are declared as an array of bytes. But it is then cast up to a structure with 16bit and 32bit members. Since GCC assumes structure alignment here, we have to force the buffers to be aligned according to the structure usage.
...
+__u8 get_vfatname_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u16))));
...
+__u8 get_dentfromdir_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u32))));
...
+__u8 do_fat_read_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u32))));
What makes you sure that a 16 resp. 32 bit alignment is sufficient, and that gcc does not decide to align such structures even stricter?
read the structures in question. the largest member is 16bit/32bit. i really dont know what other alignment gcc could randomly generate.
Wouldn't it make more sense to use "__alignof__ ()" here to be on the safe side?
i found no such alignment attribute in the gcc docs which is why i suggested Bryan use aligned(sizeof(...)). http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Function-Attributes.html http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Variable-Attributes.html http://gcc.gnu.org/onlinedocs/gcc-4.3.2/gcc/Type-Attributes.html -mike