Problem solved - A buffer length was not properly initialized. On Mon, Feb 9, 2015 at 3:50 PM, Mirko Vukovic <mirko.vuko...@gmail.com> wrote:
> Hello, > > I am running 64-bit CCL 1.10 on Windows 7. I'm writing an interface to a > National Instruments library (dll) > The library was downloaded from the NI site. It was compiled using > Microsofts C++ compiler. > > I get a stack dump when a pointer is being freed using foreign-free. This > error occurs not in a fresh lisp > session, but after a second or third call to the same function (with same > arguments). > > One more detail: the library is used to access data in files in NI's TDMS > format. This error does not > seem to happen on all files that I am trying to access, only some of them. > > I don't have much experience in cross-language library interface building, > and I am wondering if I am making > some kind of mistake. I am hoping for pointers on how to debug this > further. > > I define a pointer of type :uint to access results of a call to a library > function that places them into an > unsigned int variable. I then retrieve the value using using mem-ref, and > the free the pointer. > This is where the stack dump happens. > > What follows is the defcfun, and the lisp function. I mark with *** the > pointer, and the relevant variable > definitions that pertain to it: > > The C-function interface (with the C-documentation included) is > (defcfun (ddc-get-num-channel-group-properties > "DDC_GetNumChannelGroupProperties") > ddc-code > " > This function will get numberOfProperites (via a pointer) > > int DDC_GetNumChannelGroupProperties (DDCChannelGroupHandle channelGroup, > unsigned int *numberOfProperties); > *******" > (group-handle group-handle) ;; group-handle is define to be a pointer > type > (num-channel-group-properties :pointer)) ;;******* > > The pointer issue arises with the second variable > num-channel-group-properties. > > The lisp code where the error occurs is below (relevant lines highlighted > with ***). > > (defun get-num-channel-group-properties (group-handle*) > "Get number of file properties > > FILE-HANDLE* is a pointer to the file handle" > ;; (trace foreign-alloc) > (let ((number-of-properties > (let ((number-of-properties* (foreign-alloc :uint))) ;;****** > (print 'allocated-pointer) > (print number-of-properties*) > (ddc-get-num-channel-group-properties group-handle* > number-of-properties*) > (print 'done-with-ddc) > (prog2 > (print 'acessing-number-of-properties) > (mem-ref number-of-properties* :uint) ;; ******** > (print 'freeing-pointer) > (foreign-free number-of-properties*) ;; ******** > (print 'freed-pointer))))) > ;; (untrace foreign-alloc) > (print 'ready-to-return-with-value) > number-of-properties)) > > The traceback is: > > ALLOCATED-POINTER > #<A Foreign Pointer #x5FFC70> > DONE-WITH-DDC > ACESSING-NUMBER-OF-PROPERTIES > FREEING-POINTER > 1> Calling (FOREIGN-FREE #<A Foreign Pointer #x5FFC70>) > > and the debugger traceback is > > (#x0000000026479810) #x00000000000F532C : #<Function FREE > #x00000001000F51BF> + 365 > (#x0000000026479840) #x0000000001491314 : #<Function (TRACED FOREIGN-FREE) > #x000000210149109F> + 629 > (#x0000000026479888) #x000000000139DE14 : #<Function > GET-NUM-CHANNEL-GROUP-PROPERTIES #x000000210139DCDF> + 309 > > So, to summarize: > > I have created a pointer to access results of a library call. Library > accesses contents of files created with National > Instruments software. Library is compiled with MS C++. > > The pointer free crash occurs on the third call of the lisp function. The > first two calls (with same arguments) > run OK. > > Thanks, > > Mirko >
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