I'm writing a C++ wrapper, for Node.js, around the Outside In PDF Export library, on Ubuntu Linux. Node.js has a single threaded event loop and therefor any long-running processing is done on a worker thread. So, my wrapper is calling all of the PDF Export methods inside of this worker thread. I mention this so that you can be sure of two things: this is a threaded environment, and all PDF Export functions are being called on the same worker thread. Also, I am not making use of any redirected IO or PDF Export-handled threading. I've initialized the library specifying to use no threads. So all of this processing should be occuring within the thread that I call the functions on.
Everything seems to go fine when exporting a single PDF or even maybe two or three in quick succession. When I up the number of PDFs that I try to export to 5+, I receive a SIGSEGV segementation fault from within the OIT libs. The back trace is below:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff4fd0700 (LWP 1577)]
0x00007fffeef1da26 in HandlePoolCreateHandle () from /usr/local/lib/pdfexport/libwv_core.so
#0 0x00007fffeef1da26 in HandlePoolCreateHandle () from /usr/local/lib/pdfexport/libwv_core.so
#1 0x00007fffeef1925d in Win32VCreateHandle () from /usr/local/lib/pdfexport/libwv_core.so
#2 0x00007fffed49046b in WrapBrush(void*, GdiBrush*) () from /usr/local/lib/pdfexport/libos_pdf.so
#3 0x00007fffed46e8c8 in ?? () from /usr/local/lib/pdfexport/libos_pdf.so
#4 0x00007fffed46df63 in GNGetOutputSolutionInfoAt () from /usr/local/lib/pdfexport/libos_pdf.so
#5 0x00007fffeef1e32a in ?? () from /usr/local/lib/pdfexport/libwv_core.so
#6 0x00007fffeef1e214 in ?? () from /usr/local/lib/pdfexport/libwv_core.so
#7 0x00007fffeef18ed3 in Win32VLoadOS () from /usr/local/lib/pdfexport/libwv_core.so
#8 0x00007fffeddffb24 in VwExportOpen () from /usr/local/lib/pdfexport/libex_pagelayout.so
#9 0x00007ffff4062c4d in FAOpenExport () from /usr/local/lib/pdfexport/libsc_fa.so
#10 0x00007ffff7e53270 in EXOpenExport () from /usr/local/lib/pdfexport/libsc_ex.so
#11 0x00007ffff43c0a4d in topdf_convert(uv_work_s*) ()
#12 0x00000000006e2ec7 in worker (arg=<optimized out>) at ../deps/uv/src/unix/threadpool.c:65
#13 0x00007ffff6fa6e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#14 0x00007ffff6cd3cbd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#15 0x0000000000000000 in ?? ()
I'll explain the back trace a little. The function on #11 is the function inside my code. That is the function in which I call all of the OIT lib functions. The functions on lines #12 and higher are the Node.js-related threading functions, setting up the thread to run my code's function. Functions on lines #10 down to #1 are all the OIT-called functions.
In the documentation for PDF Export, it says that if you're going to be using this library inside a threaded environment, then you need to call the init and deinit functions each time within the worker thread. I'm doing this in my code, which you can see here: https://github.com/ryancole/topdf/blob/master/src/topdf.cc#L29-L74
Is there anything else that I need to be setting that would cause this? I'm only specifying the font directory, explicitly. Are these libraries actually thread-safe? It doesn't look like they are.
Well, upon receiving a second opinion on the meaning of the phrasing in the documentation, I have got the library working in a threaded environment now. The first parameter to DEInitEx was supposed to specify to enable PTHREAD support, which I did not have. I thought that it meant something other than it actually does.