Question

Little bit of background, I’m more experienced with Java, and have some C/C++ experience.
I’m using Visual Studios 2010.

I created two classes inside a header file and gave them fields.
It compiles ok, and for the longest time it was running just fine.
I copied the entire project directory to a new folder (all files inside) and simply recompiled and ran it. Now whenever I run it I get “Unhandled exception at 0x637779ab in RegistrationExpLib2.exe: 0xC0000005: Access violation writing location 0x00000000.” At this line

FourierTrans[i] = fftwf_plan_dft_2d(imgRows, imgCols, in[i], out[i], FFTW_FORWARD, FFTW_MEASURE);

I checked the debugger, and all of the class fields return could not evaluate expression.
I’ve already checked and the image is being read in correctly. And as far as I can tell All of the memory has been allocated correctly. fftw3 is a C dll I’m linking against.
So I’m really puzzled and was hoping someone could point out a possible issue. I’m thinking its either, I’m doing something wrong with the set up when I copied the Visual Studios Project(Even though I didn’t change anything since it was working), or I’ve incorrectly allocated memory in the header. Another issue I thought of is each image is about 20MB, so I may be messing with the heap.
I really appreciate any help.

The Images being read in are frequently 10-20MB apiece. The code is compiled as a 32 bit binary.

This is the relevent simplified portion of the code that produces the crash.

#define TESTNUM 80

//A simple test main.
int main() {
   ComplexImageFFTW a;
   ComplexImageFFTW b[TESTNUM];
   ComplexImageFFTW* ptrB;
   ptrB = b;

   printf("start\n");
   a.readImage("imagefile1", true);
   printf("Mission\n");
   for(int i = 0; i < TESTNUM; i++) {

          b[i].readImage("imagefile2", true);
   } 
   //Crash occurs here.
   FourierTrans[i] = fftwf_plan_dft_2d(imgRows, imgCols, in[i], out[i], FFTW_FORWARD, FFTW_MEASURE);
         ...
} //End main

Answer 1

Access violation writing location 0x00000000 means that you’re trying to write to memory location 0x00000000, i.e., you’re writing to a null pointer. I think the pointer p probably has the value 0.

Possibly you’re forgetting to call your Registration::setUpRegistration method?