What to do when size of the struct differs on 32 and 64 bit?
marcus at rennboot.schule.loc
Wed Aug 13 08:31:40 CDT 2008
On Tue, Aug 12, 2008 at 11:44:20PM -0600, Vitaliy Margolen wrote:
> While debugging some force-feedback issues ran into an interesting problem.
> The size of one struct from include/linux differs between 32-bit and 64-bit.
> That wouldn't be a major problem except that size is the part of the ioctl()
> request. Which results in EINVAL.
> In more details:
> #define EVIOCSFF _IOC(_IOC_WRITE, 'E', 0x80, sizeof(struct ff_effect))
> The simple test program:
> #include <linux/input.h>
> #include <stdio.h>
> int main(int argc, char * argv)
> printf("sizeof(struct ff_effect) = %d EVIOCSFF=%#x\n", sizeof(struct
> ff_effect), EVIOCSFF);
> return 0;
> $ gcc test_size.c -o test_size && ./test_size
> sizeof(struct ff_effect) = 48 EVIOCSFF=0x40304580
> $ gcc -m32 test_size.c -o test_size32 && ./test_size32
> sizeof(struct ff_effect) = 44 EVIOCSFF=0x402c4580
> The question is what do we do about it? I'm sure there are might be more
> cases like that.
The kernel is supposed to handle this transparently.
I would report this to the kernel developers, mention "32bit compatibility"
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