Cast alignment warnings

[Russ Allbery]

Russ Allbery <rra at stanford.edu> writes:
> Julien ÉLIE <julien at trigofacile.com> writes:

>> We have in timecaf/timehash an unsigned char class that is casted to an
>> unsigned int* for the sake of sscanf().

>>     n = sscanf(path, "timecaf-%02x/%02x/%04x.CF", (unsigned int*)&class, &t1, &t2);

>> I bet it is not a problem either -- because a char is 1-byte aligned,
>> so it can be cast to any other types, especially a 4-byte aligned int.
>> Please correct me if I am wrong.

> Actually, I think that one *is* a problem; the address of class is not
> guaranteed to be aligned, since it's a char, which means that sscanf may
> do an unaligned store of an integer.  It's also wrong for other reasons:
> integers are probably either four or eight bytes, so sscanf is going to
> write at least four bytes at the address of class, which is going to
> blithely overwrite neighboring variables on the stack.

Also, I think this is only going to work on little-endian systems, isn't
it?  Otherwise, it's always going to write 0 into class.

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

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