[odb-users] Use of thread local storage in ODB

[Hales, Steve]

Yes, our app does run simultaneous transactions in multiple threads. Regarding the use of another mechanism instead of __thread do you have any suggestions for how to do that? We have gotten a human involved at Apple but they tend to be rather intransigent about these things. A number of developers have complained on-line about Apple’s prohibition against __thread and Apple has announced that Xcode 8 will support the thread_local modifier introduced in C++11. We are up against a schedule deadline on this and would be most appreciative of any guidance you can provide. If it matters, we are using sqlite as our backing database with ODB.

Thanks,
Steve

From: <admin at a-cunningham.com<mailto:admin at a-cunningham.com>> on behalf of Andrew Cunningham <odb at a-cunningham.com<mailto:odb at a-cunningham.com>>
Date: Saturday, September 3, 2016 at 11:35 AM
To: "Hales, Steve" <Steve.Hales at garmin.com<mailto:Steve.Hales at garmin.com>>
Cc: "odb-users at codesynthesis.com<mailto:odb-users at codesynthesis.com>" <odb-users at codesynthesis.com<mailto:odb-users at codesynthesis.com>>
Subject: Re: [odb-users] Use of thread local storage in ODB

It depends on whether your app is running transactions in multiple threads. ODB has a concept of the "current transaction"  and the "current session" which are  variables that are TLS ( local to a thread).
You might need to come up with another mechanism if you can't use the standard __thread.

I would protest to Apple about rejecting your app. I can't see how compiling against "public" POSIX threading API's could be seen as using private APIs. Apple , of course, uses some automatic scanning of the app, maybe get a human involved.


On Fri, Sep 2, 2016 at 4:54 PM, Hales, Steve <Steve.Hales at garmin.com<mailto:Steve.Hales at garmin.com>> wrote:
My team has created an iOS app that uses ODB. We recently submitted the app to Apple to be published in the app store. Our app was rejected due to the presence of the symbol "__tlv_bootstrap" which Apple considers to be part of an unapproved private API. Our research indicates that this symbol results from use of the "__thread" modifier to create a thread local variable. The only place we can find __thread in our code is in the ODB header tls.hxx where it appears to take effect when POSIX threads are enabled. When we built the ODB library for our app we specified --enable-threads in the configure step. Can you tell us if that header, specifically the __thread use, is likely to be included in our code? If so, would rebuilding ODB with threads disabled remove it? And what effect might that have on our app?

Thanks,
Steve

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