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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When using the IANA tz data and code (version 2017B) on AIX and/or HPUX, I got core dumps.
<o:p></o:p></p>
<p class="MsoNormal">I was not able to figure out the root cause, but after I had renamed the timezone, daylight and tzname variables to something else (i.e., prefixed with olson_), the error disappeared.<o:p></o:p></p>
<p class="MsoNormal">A similar crash happened on AIX 7.2, but in only one test case (compared to all our test cases on AIX 7.1 and HPUX 11.31). I don’t have a good explanation for the different behavior between AIX 7.1 and 7.2.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The tz code was incorporated into two parts of our product:<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l2 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>The tzcode was built with USG_COMPAT enabled, i.e. timezone, daylight and tzname symbols are used and incorporated into our binaries<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l2 level1 lfo1">
<![if !supportLists]><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>The tzcode was also built into a shared library that uses another shared library that calls some of the time functions from libc (e.g. tzset(), or gettimeofday())<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">BTW: in our code, I’m renaming (using defines) all tz functions too, and prefix them with ‘olson_’. So, at symbol level, no duplicates between system functions and TZ code functions should exist.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In our code, the error happened under the following circumstances:<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo2">
<![if !supportLists]><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>A binary of us is using the tz library (using USG_COMPAT)<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo2">
<![if !supportLists]><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>That binary loads dynamically (with dlopen(), with RTLD_GLOBAL flag) another shared library of us, also containing the tz library<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo2">
<![if !supportLists]><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>A 3<sup>rd</sup> party shared library was loaded by our own shared library. Also with dlopen/RTLD_GLOBAL flag.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Both our binary (#1) a shared library (#2) were creating using export lists/versions scripts. None of the tz code or variables was exported. And our shared library is using a flag that forces the loader to perform ‘innermost symbol resolution’
(in such way that C++ exceptions still work). The 3<sup>rd</sup> party library was either the Oracle or DB2 client database library. Both perform a call to libc that triggers a time function (gettimeofday() or tzset()).<o:p></o:p></p>
<p class="MsoNormal">The core dump happens in libc, on one of the time functions, called by the 3<sup>rd</sup> party shared library.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Using IANA tz functions from our binaries, without loading 3<sup>rd</sup> party shared libraries works fine.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hypothesis: the fact that the tzcode (compiled with USG_COMPAT) changes (one of) the (libc exported) timezone, daylight, tzname, causes the time functions in libc to crash.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Notes:<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l1 level1 lfo3">
<![if !supportLists]><span style="mso-list:Ignore">a.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>making timezone, daylight, tzname static in the IANA localtime.c and added a get_xxx function did not help either.<o:p></o:p></p>
<p class="MsoListParagraph" style="margin-left:.25in;text-indent:-.25in;mso-list:l1 level1 lfo3">
<![if !supportLists]><span style="mso-list:Ignore">b.<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Building without USG_COMPAT did not help either.<o:p></o:p></p>
<p class="MsoNormal">It is quite strange that none of these both (#a and #b) did help, but I lack time to do more research. As I now have a suitable workaround (by renaming/prefixing involved variables), it is fine for me now.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This mail is just intended to inform about conflicts/core dumps, most probably related to ‘similar named’ variables with the system libc (and thus generate a trap on some platforms).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If the tz code can get changed (ever/in the future) to prevent such conflicts, it would be great. No other action is needed (by me) for now.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Kees<o:p></o:p></p>
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