Patch to expand tz checking scope in TimeZone_md.c

Wed Nov 9 19:09:22 PST 2011

On 11/09/11 03:01, Jonathan Lu wrote:
> On 11/04/2011 01:26 PM, David Holmes wrote:
>> On 4/11/2011 2:53 PM, David Holmes wrote:
>>> On 4/11/2011 2:13 PM, Masayoshi Okutsu wrote:
>>>> Probably the difference isn't documented. I tried Solaris 10 and Ubuntu
>>>> 10.03. The difference still exists.
>>>>
>>>> Solaris 10:
>>>> $ unset TZ
>>>> $ date
>>>> Fri Nov 4 13:04:45 JST 2011
>>>> $ TZ="" date
>>>> Fri Nov 4 13:04:53 JST 2011
>>>>
>>>> Ubuntu 10.04:
>>>> $ unset TZ
>>>> $ date
>>>> Fri Nov 4 13:05:50 JST 2011
>>>> $ TZ="" date
>>>> Fri Nov 4 04:05:55 UTC 2011
>>>>
>>>> When the TZ value is an empty string, Ubuntu uses UTC while Solaris
>>>> still looks up the system default.
>>>
>>> I have to take back my comment regarding this not seeming to be platform
>>> specific code - it is highly platform specific! It seems that on Linux
>>> we are happy to report a TZ of "" but not so on Solaris. I presume this
>>> is an attempt to keep Java's use of TZ consistent with how other apps
>>> handle it on that platform. (environ(5) gives a little insight on
>>> Solaris as to how TZ is used.)
>>>
>>> So the key thing here is to not disturb the existing behaviour on either
>>> linux or Solaris - which suggests the original patch. That said I'm not
>>> convinced - given this is so platform specific - that simply treating
>>> non-linux the same as Solaris is a reasonable thing to do. I think it
>>> would be useful to see what the BSD/OSX port(s) had to do with this code
>>> - if anything.
>>
>> To answer my own queries BSD/OSX does
>>
>>       511 #if defined(__linux__) || defined(_ALLBSD_SOURCE)
>>       512     if (tz == NULL) {
>>       513 #else
>>       514 #ifdef __solaris__
>>       515     if (tz == NULL || *tz == '\0') {
>>       516 #endif
>>       517 #endif
>>
>> so the suggested patch would at least not interfere.
>>
>> Anyway this needs input from other core-libs folk. I didn't intend to 
>> get quite so heavily involved. ;-)
>>
>> David
>> -----
>>
>>
>>
>>> David
>>> -----
>>>
>>>
>>>> Thanks,
>>>> Masayoshi
>>>>
>>>> On 11/3/2011 4:16 PM, Jonathan Lu wrote:
>>>>> Hi Masayoshi,
>>>>>
>>>>> I did find some references about date-time related functions / TZ
>>>>> variables on Linux but got only a few about Solaris, so could not see
>>>>> any differences between those two platforms about the changes
>>>>> described in my patch. Have you got any links or references about
>>>>> these differences? I'm interested in it and may update the patch again
>>>>> after reading them.
>>>>>
>>>>> Thanks a lot!
>>>>> - Jonathan
>>>>>
>>>>> On 11/02/2011 10:27 PM, Masayoshi Okutsu wrote:
>>>>>> Hi Jonathan,
>>>>>>
>>>>>> IIRC, the difference came from some behavioral difference between the
>>>>>> Linux and Solaris libc date-time functions and/or the date command,
>>>>>> and TimeZone_md.c tries to follow the difference. But the code was
>>>>>> written looooong ago. The difference may no longer exist.
>>>>>>
>>>>>> Thanks,
>>>>>> Masayoshi
>>>>>>
>>>>>> On 11/2/2011 8:39 PM, Jonathan Lu wrote:
>>>>>>> On 11/02/2011 07:00 PM, David Holmes wrote:
>>>>>>>> On 2/11/2011 7:01 PM, Jonathan Lu wrote:
>>>>>>>>> On 11/02/2011 04:56 PM, Jonathan Lu wrote:
>>>>>>>>>> Hi core-libs-dev,
>>>>>>>>>>
>>>>>>>>>> In jdk/src/solaris/native/java/util/TimeZone_md.c, starting from
>>>>>>>>>> line
>>>>>>>>>> 626, I found that the scope of "#ifdef __solaris__" might be too
>>>>>>>>>> narrow, since it also works for some kind of OS which I'm 
>>>>>>>>>> currently
>>>>>>>>>> working on, such as AIX.
>>>>>>>>>> So I suggest to just remove the '#ifdef __solaris__' and leave 
>>>>>>>>>> the
>>>>>>>>>> "#else" to accommodate more conditions, see attachment
>>>>>>>>>> 'patch.diff'. I
>>>>>>>>>> think this may enhance the cross-platform ability, any ideas 
>>>>>>>>>> about
>>>>>>>>>> this modification?
>>>>>>>>>>
>>>>>>>>>> Regards
>>>>>>>>>> - Jonathan Lu
>>>>>>>>> I'm not sure why the attachment got filtered, here paste it to the
>>>>>>>>> mail
>>>>>>>>> content directly.
>>>>>>>>>
>>>>>>>>> diff -r 4788745572ef src/solaris/native/java/util/TimeZone_md.c
>>>>>>>>> --- a/src/solaris/native/java/util/TimeZone_md.c Mon Oct 17 
>>>>>>>>> 19:06:53
>>>>>>>>> 2011 -0700
>>>>>>>>> +++ b/src/solaris/native/java/util/TimeZone_md.c Thu Oct 20 
>>>>>>>>> 13:43:47
>>>>>>>>> 2011 +0800
>>>>>>>>> @@ -626,10 +626,8 @@
>>>>>>>>> #ifdef __linux__
>>>>>>>>> if (tz == NULL) {
>>>>>>>>> #else
>>>>>>>>> -#ifdef __solaris__
>>>>>>>>> if (tz == NULL || *tz == '\0') {
>>>>>>>>> #endif
>>>>>>>>> -#endif
>>>>>>>>> tz = getPlatformTimeZoneID();
>>>>>>>>> freetz = tz;
>>>>>>>>> }
>>>>>>>>
>>>>>>>> I'm unclear why any of that code needs to be platform specific - is
>>>>>>>> an empty TZ string somehow valid on linux? I would have thought the
>>>>>>>> following would be platform neutral:
>>>>>>>>
>>>>>>>> if (tz == NULL || *tz == '\0') {
>>>>>>>> tz = getPlatformTimeZoneID();
>>>>>>>> freetz = tz;
>>>>>>>> }
>>>>>>>>
>>>>>>> Hi David,
>>>>>>>
>>>>>>> getenv("TZ") returns NULL when TZ environment variable is not set at
>>>>>>> all and returns '\0' when TZ was exported as empty string. After
>>>>>>> more checking for both cases, I agree with you, nothing useful can
>>>>>>> be retrieved from that environment variable.
>>>>>>> So I changed the patch to this,
>>>>>>>
>>>>>>> diff -r 7ab0d613cd1a src/solaris/native/java/util/TimeZone_md.c
>>>>>>> --- a/src/solaris/native/java/util/TimeZone_md.c Thu Oct 20 10:32:47
>>>>>>> 2011 -0700
>>>>>>> +++ b/src/solaris/native/java/util/TimeZone_md.c Wed Nov 02 19:34:51
>>>>>>> 2011 +0800
>>>>>>> @@ -623,13 +623,7 @@
>>>>>>>
>>>>>>> tz = getenv("TZ");
>>>>>>>
>>>>>>> -#ifdef __linux__
>>>>>>> - if (tz == NULL) {
>>>>>>> -#else
>>>>>>> -#ifdef __solaris__
>>>>>>> if (tz == NULL || *tz == '\0') {
>>>>>>> -#endif
>>>>>>> -#endif
>>>>>>> tz = getPlatformTimeZoneID();
>>>>>>> freetz = tz;
>>>>>>> }
>>>>>>>
>>>>>>>> David
>>>>>>>> -----
>>>>>>>>
>>>>>>>>> Regards
>>>>>>>>> - Jonathan Lu
>>>>>>> Regards
>>>>>>>
>>>>>>> - Jonathan
>>>>>>>
>>>>>
> Copy to bsd-port-dev and macosx-port-dev lists to see if anybody here 
> has some ideas about this issue.

Hi Jonathan,

The above email is a bit hard to follow due to the mixture of top and
bottom replies.

I can confirm that OpenBSD and Mac OS X 10.5.8 follow the Linux behavior
which confirms the need for platform ifdef's in this code.

Seems like you need to make the following change:

-#ifdef __solaris__
+#if defined(__solaris__) || defined(__AIX__)

or something similar to maintain compatibility.

In general the approach taken for adding BSD support was to never
assume you can change other supported code paths. If your architecture
follows an existing code path behavior add it like I did above.
Otherwise just create a #ifdef myarch section for it.

Unifying or changing another architecture's code path requires access
to the arch, research and confirmation that the change is ok. Typically
this may be done by writing independent test programs and running them
on each arch.

Regards,
-Kurt