Re: [gdal-dev] Get error handler user data when removing CPL Error Handler
Thanks, that does make sense. Fortunately, like py, Rust also has closures, so user data could be handled directly by the caller. We're also pushing for an impl. without user-data support. The thread local APIs should also be supported (not done yet though); should be much simpler as it doesn't involve concurrency. On Sun, Sep 12, 2021 at 9:53 PM Sean Gillies wrote: > Hi, > > For what it's worth, In the Python package named rasterio we're using the > push/pop API: > https://github.com/mapbox/rasterio/blob/master/rasterio/_env.pyx#L336. > While Rust's needs may differ, a single handler without any support for > user data works well for Python: everything goes to the logging > infrastructure, one of the kind of globals that Howard refers to in > https://github.com/OSGeo/gdal/blob/master/gdal/doc/source/development/rfc/rfc37_cplerror_userdata.rst#rationale, > and Python developers extend the logger if they want behavior that is > different from the basic defaults. > > On Sun, Sep 12, 2021 at 8:12 AM Even Rouault > wrote: > >> Hi, >> >> no there's no thread safe API to do what you want. You'd need a new >> function >> >> CPLErrorHandler CPLSetErrorHandlerEx2( CPLErrorHandler >> pfnErrorHandlerNew, void* pUserData, void** ppOldUserData ) >> >> to do that. >> >> But as you mention threads that might compete to set an error handler, >> using CPLSetErrorHandlerEx() is probably not the best strategy. You'd be >> better with CPLPushErrorHandler() / CPLPopErrorHandler() that only affects >> the current thread. >> >> Even >> Le 12/09/2021 à 16:03, Rajsekar Manokaran a écrit : >> >> Hi, >> >> In the gdal rust bindings (https://github.com/georust/gdal), we're >> trying to facilitate the use of CPLSetErrorHandlerEx and related APIs. >> While setting a handler, we may pass a heap allocated data pointer to the >> second argument, which is then read via the CPLGetErrorHandlerUserData in >> the handler and passed to the user. >> >> However, while removing or setting another handler, we're unable to find >> a race-free method to get the associated user data of the previous >> handler. This is needed to properly deallocate the memory. >> >> Is there an atomic way to get both the previous handler (as returned by >> CPLSetErrorHandler), along with the associated user data? The issue with >> making two calls, is that another thread might make changes in between the >> two calls. >> >> We could synchronize in our API, but it still has the same issue if the >> user parallely used the C APIs directly or via a different interface. >> >> Relevant PR in rust gdal bindings: >> https://github.com/georust/gdal/pull/215 >> >> - >> Regards >> >> > > -- > Sean Gillies > ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Get error handler user data when removing CPL Error Handler
Hi, For what it's worth, In the Python package named rasterio we're using the push/pop API: https://github.com/mapbox/rasterio/blob/master/rasterio/_env.pyx#L336. While Rust's needs may differ, a single handler without any support for user data works well for Python: everything goes to the logging infrastructure, one of the kind of globals that Howard refers to in https://github.com/OSGeo/gdal/blob/master/gdal/doc/source/development/rfc/rfc37_cplerror_userdata.rst#rationale, and Python developers extend the logger if they want behavior that is different from the basic defaults. On Sun, Sep 12, 2021 at 8:12 AM Even Rouault wrote: > Hi, > > no there's no thread safe API to do what you want. You'd need a new > function > > CPLErrorHandler CPLSetErrorHandlerEx2( CPLErrorHandler pfnErrorHandlerNew, > void* pUserData, void** ppOldUserData ) > > to do that. > > But as you mention threads that might compete to set an error handler, > using CPLSetErrorHandlerEx() is probably not the best strategy. You'd be > better with CPLPushErrorHandler() / CPLPopErrorHandler() that only affects > the current thread. > > Even > Le 12/09/2021 à 16:03, Rajsekar Manokaran a écrit : > > Hi, > > In the gdal rust bindings (https://github.com/georust/gdal), we're trying > to facilitate the use of CPLSetErrorHandlerEx and related APIs. While > setting a handler, we may pass a heap allocated data pointer to the second > argument, which is then read via the CPLGetErrorHandlerUserData in the > handler and passed to the user. > > However, while removing or setting another handler, we're unable to find a > race-free method to get the associated user data of the previous handler. > This is needed to properly deallocate the memory. > > Is there an atomic way to get both the previous handler (as returned by > CPLSetErrorHandler), along with the associated user data? The issue with > making two calls, is that another thread might make changes in between the > two calls. > > We could synchronize in our API, but it still has the same issue if the > user parallely used the C APIs directly or via a different interface. > > Relevant PR in rust gdal bindings: > https://github.com/georust/gdal/pull/215 > > - > Regards > > -- Sean Gillies ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Get error handler user data when removing CPL Error Handler
Thanks for the clarification! The API you suggest would indeed be quite convenient. We do intend to support the thread local variants too, but wanted to see how much we can support the global one. - Regards On Sun, Sep 12, 2021 at 7:42 PM Even Rouault wrote: > Hi, > > no there's no thread safe API to do what you want. You'd need a new > function > > CPLErrorHandler CPLSetErrorHandlerEx2( CPLErrorHandler pfnErrorHandlerNew, > void* pUserData, void** ppOldUserData ) > > to do that. > > But as you mention threads that might compete to set an error handler, > using CPLSetErrorHandlerEx() is probably not the best strategy. You'd be > better with CPLPushErrorHandler() / CPLPopErrorHandler() that only affects > the current thread. > > Even > Le 12/09/2021 à 16:03, Rajsekar Manokaran a écrit : > > Hi, > > In the gdal rust bindings (https://github.com/georust/gdal), we're trying > to facilitate the use of CPLSetErrorHandlerEx and related APIs. While > setting a handler, we may pass a heap allocated data pointer to the second > argument, which is then read via the CPLGetErrorHandlerUserData in the > handler and passed to the user. > > However, while removing or setting another handler, we're unable to find a > race-free method to get the associated user data of the previous handler. > This is needed to properly deallocate the memory. > > Is there an atomic way to get both the previous handler (as returned by > CPLSetErrorHandler), along with the associated user data? The issue with > making two calls, is that another thread might make changes in between the > two calls. > > We could synchronize in our API, but it still has the same issue if the > user parallely used the C APIs directly or via a different interface. > > Relevant PR in rust gdal bindings: > https://github.com/georust/gdal/pull/215 > > - > Regards > > > ___ > gdal-dev mailing > listgdal-dev@lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/gdal-dev > > -- http://www.spatialys.com > My software is free, but my time generally not. > > ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
[gdal-dev] Get error handler user data when removing CPL Error Handler
Hi, In the gdal rust bindings (https://github.com/georust/gdal), we're trying to facilitate the use of CPLSetErrorHandlerEx and related APIs. While setting a handler, we may pass a heap allocated data pointer to the second argument, which is then read via the CPLGetErrorHandlerUserData in the handler and passed to the user. However, while removing or setting another handler, we're unable to find a race-free method to get the associated user data of the previous handler. This is needed to properly deallocate the memory. Is there an atomic way to get both the previous handler (as returned by CPLSetErrorHandler), along with the associated user data? The issue with making two calls, is that another thread might make changes in between the two calls. We could synchronize in our API, but it still has the same issue if the user parallely used the C APIs directly or via a different interface. Relevant PR in rust gdal bindings: https://github.com/georust/gdal/pull/215 - Regards ___ gdal-dev mailing list gdal-dev@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/gdal-dev
