Unaligned access to packed structs on ppc405
Mon Jan 30 12:03:00 GMT 2006
David Edelsohn wrote:
>>>>>>Yaro Pollak writes:
>>I am cross-compiling on GCC 3.4.1 for the PowerPC 405, which can handle
>>unaligned accesses in hardware.
>>Whenever I am accessing members of a packed bit-struct by pointer, the
>>compiler produces byte accesses, instead of 4-byte acceses.
>>I've tried to use |-mstrict-align but to no avail.
> What does "|-mstrict-align" mean? -mstrict-align means "do not
>assume that unaligned accesses are handled by the system." You are
>requesting that the compiler assume the target requires strict alignment
>and then questioning why it is accessing a packed bit-struct assuming the
Yes, I actually couldn't tell whether I should use -mno-strict-align or
-mstrict-align from the explanation in GCC documentation (thank you for
your explanation) so I tried both, but it didn't matter at all. I guess
I should have mentioned that before. Perhaps any other ideas? I feel it
is something fundamental that I keep missing.
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