What to do when size of the struct differs on 32 and 64 bit?
anssi.hannula at gmail.com
Sun Sep 21 03:55:03 CDT 2008
Marcus Meissner wrote:
> 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"
> or so.
Just for the record, it has been fixed for 2.6.27:
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