splinkersets01 test assumptions

Kinsey Moore kinsey.moore at oarcorp.com
Wed Feb 17 16:41:19 UTC 2021

> On 17/02/2021 16:32, Kinsey Moore wrote:
>>>           .section        .rtemsroset.s.begin,"a"
>>>           .align  8
>>>           .type   _Linker_set_s_begin, %object
>>>           .size   _Linker_set_s_begin, 0
>>> _Linker_set_s_begin:
>>>           .section        .rtemsroset.s.end,"a"
>>>           .align  8
>>>           .type   _Linker_set_s_end, %object
>>>           .size   _Linker_set_s_end, 0
>>> _Linker_set_s_end:
>>>           .ident  "GCC: (GNU) 10.2.1 20210205 (RTEMS 6, RSB
>>> 61dcadee0825867ebe51f9f367430ef75b8fe9c0, Newlib d4a756f)"
>>>> <snip>
>>> I would remove the SUBALIGN() from the linker script. You can also add a
>>> new test case for splinkersets01 similar to struct s from above. Then we
>>> should check if the test fails on aarch64 and why it fails.
>> The example above actually shows the issue I'm having in _Linker_set_i_begin and _Linker_set_i_end. The alignment expands for the larger struct, but does not shrink for data types smaller than 8 bytes, leaving padding that the test interprets as additional space in the linker set.
> I still don't see why a larger alignment is an issue. The begin/end 
> objects have a size of zero. Where do you observe a padding?

Even when the begin/end objects have a size of 0, they're aligned out to 8 bytes forcing empty bytes if the content does not exactly fill a multiple of 8 bytes. Those non-content bytes are counted as part of the section.


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