wxConvFile (and wxFileExists) not thread safe on Mac

[Stefan Csomor]

Hi Joost
>
> I'm encountering occasional crashes in the mac version of my app, 
> related to the simultaneous use of wxFileExists in multiple threads. 
> I've narrowed the problem down to the following test case:
>
>   for(int i=0; i < 100000; i++)
>   {
>     wxConvFile.WC2MB(NULL, wxT("Test"), 0);
>   }
>
> If this is executed in two threads simultaneously, an access violation 
> occurs.
>
> wxConvFile is actually a global wxMBConv_macUTF8D object 
> (strconv.cpp). It has three member variables, which are used 
> internally in calls to OSX character set conversion functions. 
> Apparently these members are modified during the conversion, causing a 
> clash when multiple threads are doing a conversion simultaneously 
> using the same global conversion object.
>
> Bottom line is that wxFileExists is not thread safe, and probably any 
> function that accesses a file based on its file name!
>
> I'd like to fix it somehow, but I'm not familiar with the OSX specific 
> functions used in wxMBConv_macUTF8D.
thanks for spotting this, unfortunately I haven't found any clues on 
Apple's site as which parts of the implementation might not be thread 
safe, do you always get the stack trace ?

Thanks,

Stefan

Joost wrote: