Re: Crash when re-initializing as static library

[Klaus Fischer <klaus.fischer@tara-systems.de>]

Hi Ross,

great, it's nice to hear that! :)

I am currently also in touch with Marcelo Roberto Jimenez from libupnp 
over at Sourceforge.net regarding this issue:

https://sourceforge.net/p/pupnp/bugs/119/

He sent me a patch for the latest libupnp that eliminated the calls to 
pthread_win32_process_*() inside libupnp when using PTW32 as static 
library as you suggested, as long as I had a correct understanding of 
your quoted passage from README.NONPORTABLE. I have applied that patch, 
but now I am facing the problem that libupnp hangs indefinitely in a 
call to pthread_cond_wait().

It looks to me that pthread_win32_process_attach_np() was not called 
automatically at application start-up. When my application hits the 
breakpoint right before the call to the blocking pthread_cond_wait(), 
the global variable "ptw32_processInitialized" is still 0, although it 
should have been set to 1 inside pthread_win32_process_attach_np().

I actually don't understand how that function can be called 
automatically at application start-up when building PTW32 as a static 
library. How is this achieved? AFAIK there is no DllMain-equivalent for 
static libraries. Am I wrong here? Or is it maybe that I'm using Visual 
Studio 2005 and it doesn't support that? Are there any options to 
activate in the project solution for doing so? I should mention that I'm 
not using the Visual Studio 6.0 project files delivered with PTW32, 
since Visual Studio 2005 tells me it "Cannot load the project due to a 
corrupt project file.".

Thanks for any help here, and also for your quick and kind response!

Best regards,
Klaus


On 08.11.2013 00:47, Ross Johnson wrote:
> Hi Klaus,
>
> Thanks for providing the extra context. I'll apply your suggested
> change/s, probably early next week.
>
> Regards.
> Ross
>
> On 8/11/2013 1:19 AM, Klaus Fischer wrote:
>> Let me give you a little background in order to understand my situation:
>>
>> I'm actually using the Portable SDK for UPnP Devices (libupnp), which
>> in turn relies on pthreads. I'm developing cross-plattform
>> (Windows/Linux), so I need Pthread-Win32 (henceforth called PTW32) to
>> enable libupnp to run under Windows.
>>
>> libupnp in turn initializes and deinitializes PTW32 every time libupnp
>> itself gets initialized/deinitialized. De-/initialization of PTW32 is
>> explicitly done via pthread_win32_process_* when libupnp is compiled
>> for WIN32 and PTW32 is used as a static library. This is still done
>> that way in the latest libupnp release (1.6.18).
>>
>> One of my first tests was to repeatedly call UpnpInit()/UpnpFinish()
>> to check for general stability, which is also always a good test for
>> software cleanliness according to my experience; unfortunately, this
>> immediately resulted in the access violation in PTW32.
>>
>> It looks like libupnp still has to adapt to the changed calling
>> behavior of PTW32, although they had plenty of time for it (the latest
>> libupnp release is from January 2013, while the latest PTW32 is from
>> May 2012). They probably overlooked the change in calling
>> pthread_win32_process_*; I will send them a note for it.
>>
>> Nevertheless, I will continue to use my locally patched version of
>> PTW32 until either libupnp adapted to the changed PTW32 behavior or
>> PTW32 is available with initialization of globals during the attaching
>> phase. I've ran into the same problem in some of my libraries too, and
>> decided to give my globals a proper initialization in an
>> Init()-function to avoid such issues during repeated
>> de-/initialization. It would be nice if you could consider doing this
>> in PTW32 too, just for the sake of backwards-compatibility (if this
>> actually worked in pre-2.9.0 versions).
>>
>> Best regards,
>> Klaus
>>
>>
>> > Hi,
>> >
>> > Applications statically linked with current versions of the library
>> no longer need to call those routines explicitly. From
>> README.NONPORTABLE:
>> >
>> >     These functions contain the code normally run via DllMain
>> >     when the library is used as a dll. As of version 2.9.0 of the
>> >     library, static builds using either MSC or GCC will call
>> >     pthread_win32_process_* automatically at application startup and
>> >     exit respectively.
>> >
>> > But you are also detaching and reattaching within the same process,
>> which is unintended use. Is this how you expect to use the library or
>> are you just analysing?
>> >
>> >> On 7/11/2013 4:53 AM, Klaus Fischer wrote:
>> >> Dear pthreads-win32 developers,
>> >>
>> >> I have experienced a crash when building pthreads-win32 as static
>> library and re-initializing it using the following sequence:
>> >>
>> >> - pthread_win32_process_attach_np()
>> >> - pthread_win32_process_detach_np()
>> >> - pthread_win32_process_attach_np()
>> >>
>> >> The global variable ptw32_threadReuseTop still points to memory
>> used between the first attach/detach run, but this memory was already
>> freed in function ptw32_processTerminate(), which was called during
>> detaching.
>> >>
>> >> When using e.g. pthread_self() afterwards, the global
>> ptw32_threadReuseTop now points to invalid memory, causing an access
>> violation writing to that memory location.
>> >>
>> >> A simple code change fixed that problem by assigning the default
>> value PTW32_THREAD_REUSE_EMPTY to that global variable at the end of
>> function ptw32_processTerminate(), after the while loop freeing all
>> still allocated thread handles.
>> >>
>> >> A better way to fix that would probably be to initialize all the
>> library globals of global.c during the attaching stage. In a static
>> library, those globals are only initialized once when the process
>> starts, but _should_ be re-initialized on every attach.
>> >>
>> >> I know this is not a concern when using this library as dynamic
>> library, but since there is an option to use it as static library and
>> other people also use it that way according to the mailing list, it
>> would be great if it could survive multiple re-initializations.
>> >>
>> >> Thanks in advance,
>> >> Klaus
>

-- 
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Dipl. Inf. Klaus FISCHER  -  Software Engineer

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