On 13.03.2016 00:57, Stefan Tauner wrote:
> On Sun, 13 Mar 2016 00:26:41 +0100
> Carl-Daniel Hailfinger <c-d.hailfinger.devel.2...@gmx.net> wrote:
>
>> On 13.03.2016 00:05, Stefan Tauner wrote:
>>> This came up when I was testing if building on SunOS still works
>>> on the buildbot's instance of OmniOS r151014 which is based on illumos.
>>>
>>> The fix is
>>> - to link against libnsl
>>> - a small C type fix in ich_descriptor_tool
>>>
>>> Signed-off-by: Stefan Tauner <stefan.tau...@alumni.tuwien.ac.at>
>>> Acked-by: Stefan Tauner <stefan.tau...@alumni.tuwien.ac.at>
>>>
>>> diff --git a/util/ich_descriptors_tool/ich_descriptors_tool.c
>>> b/util/ich_descriptors_tool/ich_descriptors_tool.c
>>> index c3d9ba1..ad3b6f0 100644
>>> --- a/util/ich_descriptors_tool/ich_descriptors_tool.c
>>> +++ b/util/ich_descriptors_tool/ich_descriptors_tool.c
>>> @@ -170,7 +170,7 @@ int main(int argc, char *argv[])
>>> usage(argv, "Seeking to the end of the file failed");
>>>
>>> #ifdef HAVE_MMAP
>>> - buf = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
>>> + buf = (uint32_t *)mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
>> The compiler may require that to stop complaining, but AFAICS there is a
>> real bug behind this. buf is sometimes casted to uint8_t *, and unless
>> I'm too sleepy already, this buffer violates the strict aliasing rules.
>> We can solve this with -fno-strict-aliasing, or fix the code. With a
>> code fix, in theory the problem should go away.
> While this is true it does not make much sense to try to fix it:
> - all accesses are read-only. The compiler can re-order as much as it
> wants, we won't get wrong results. No compiler writers however mean
> will make this explode. And that's the only potential problem with
> aliasing.
> - ich_descriptor.c intentionally uses undefined behavior by writing to
> some struct members and reading it through others to spare us from
> bit-shifting/masking. That was discussed at length back when I added
> it and since we use the code on x86 only it is fine.
Ah right.
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2...@gmx.net>
>>> if (buf == (void *) -1)
>>> #endif
>>> {
>>
>> Side note (no need to fix this right now)
>> util/ich_descriptors_tool/ich_descriptors_tool.c:182
>> if (len != read(fd, buf, len))
>> usage(argv, "Seeking to the end of the file
>> failed");
>> Somehow that error message doesn't fit with the code.
> Copy and paste error from :170. Fixed in tested_stuff, thanks!
Thanks.
Regards,
Carl-Daniel
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